10

Abstract Th is chapter presents a paleoecological analysis of nonshycamivorous Sanlacrucian marsupials of the orders Paucitubershyculara and Microbiothelia Different ecological niches are infen-ed [Tom estimates of bcxIy mass diet and iocomOior behavior Body masses were estimated using a regression analysis based on living marsupials Possible dietary prefershyences were explored by an analys is of the developmeut ofmolar shearing crests Inferences about locomotor behaviors of some species with well -preserved postcran iaJ skeletal remains were deJived from a publ is hed morphofunctional analysis From the wide range of estimated body masses and diet several niches were infened small- to medium-sized insecti vores small- to medium-sized insectivore-frugivores and medium- to largeshysized fmgivores According to our results Paucituberclilata and Microbiothelia of thc Sant1 Cruz FonnatiQJl conStilule an ecoshylogically diverse assemblage tbat inhabited forested habitats developed under wltum temperanlres and seasonaj rainfall These fores ted habitats could have supported severn] nnn-carshynivorous marsupi~1 niches offering diverse resources both in the spatial dimensions and ill the lrophic ones

Resumen En eS le capitulo se presenta un ana lisis paleoecologico de los mars upiales no carn ivoros del Santacrucense perteneshycientes a los 6rdenes PHlcituberculata y Microbio the ri a Para establecer los dislinlos nichos ecologicos se anali shyzaron las masas corporales d ietas y eSlJltt tegialt locomoshyloras El tamafio cOlx)ral fue es ti mado a partir de una recta de regrcsion liuear obtenida a part ir de marsupiales actuaJes Las pos ibles prefe renc ias dietarias fueron explorshyadas mediante un anaJi5is del grado de desalTo llo de las crestas cortantes de los molares L1s es trateg ias locomotoras en e l easo de aqllelJas especies que poseen un esque leto postcraneano bien preservado fueron infershyidas a partir de un amili sis morfofunciona1 A partir del

Early Miocelle Paleobiology ill Paragonia Hi~h-Lolifllde

Paleocommunities of he Sama Cmz Formaioll ed Sergio F Vizcaino Ri chard F Kay and M Susana Bargo Published by Cambridge Uni vtrsil Y Press (C Cltlmbridge Univers ity Press 2012

156

Paleoecology of the Paucituberculata and Microbiotheria (Mammalia Marsupialia) from the late Early Miocene of Patagonia Mara Alejandro Aluilo Edgardo Ortiz-JaureguizaT

anti Adriana M Candela

ami li sis de los result ados de las mas as corporales y [a dietas se reconocieran diversos nichos ecologicos pequenos a medianos insec tivoros pequenos a medianos insecliv oros~ frug ivoros y medianos a grandes ft1Jgivoros Nuestros resultados nos pemliten coneluir que los Pauejshytu berculata y los Microbio the ria de la FOlmaci6n Santa Cruz constituyen ull agregado ecologicamente diverso que habit6 zonas boscosas desarrolladas bajo un c lima calido y con lIuvias es tac ionales ESlas zonas habrian ofrecido una amplia diversidad de recursos fanlo espashyciale- como troficos para los diversos ni chos ecologicos de los marslipiaies no ca rn lvo ros Nuestfa reconstrucci6n paleoam biental es compatible con la ex isrenc ia de heteroshygeneidad arnbie nl al dmante el SanlltlCfUCenSe inferenc ia est deri vada de otras indicadores c limatico-ambienlltlles

101 Introduction

During the Cenozoic a high dive rsity of mctatherians occupied

a broad range of ecological niches jn South America This

array included medium 10 IMge carn ivorous and cami vorousshy

omnivorous (ie Sparassodonra Prevosti e aI Chapter [I )

small granivorous (eg poJydolopimOlphian ArgyroJagoidea

Goin el a in press) and several sma ll to medium insectivorous

and insectivorolis-flUgivorou ~ spec ies (eg didelphimorphian

Didelphidae Paucitubercu lata Gain (( al in press Dumont

el aI 2000) All of the larger taxa are now ex tinct and a fe~

of the small- to medium-sized insecti vorous insec ti vorous-shy

fmgivorous and carnivorous taxa (microbiotherians paucirushy

berculatans and didelphids) surv ive to the presenl

Pallcituberculata and Microbiotheria are two major

Marsupia lia clades (Fig 101) As a result of all current

phyl ogeJli e~ (eg Amrine-Madsen el 01 2003 Horovitz amI

Sanchezmiddot ViUagra 2003 Phillips cf aI 2006 Asher ef al 2001 Nilsson el al 2004 Beck 2008 Meredith el 01 20081 there is consensus on Ihe close affinities between (he extruu

microbiotheriid Dromiciops gliroides and the A ustralasian

marsupials (Ausualidelphia Szalay 1982 1994) However the pos ilion of D gfiroides wi thin AustralicJelphia js srill

con trover~ i a J (Nilson et 01 20JO) On the othe r hand mo~

157 Paleoec RY of Santacrucian Pauciruherculata alld Microhiotheria

--------_________ remMonol ~l~

--_----------- -- Vmcelesfes

Euthaflll

------------ DeJlellleriClum

-_________ Pucadffphys

--------- CMolphlll1orpllta

-______ Paucltubercullta

-____ Oasywomorphla

-___ Pernmella

Microbiothera

Diprolodon tJa

Fig 101 Phylogenetic Iree showing the relationships of li ving marsupial oruers (modified from HoroviTz and Srinchez~Villagra 2003 )

phylogenetic studies based on molecular or combined data (eg Nilson et al 2004 Asher et aI 2004 Beck 2008 Meredi th ef 0 2008) as well as some morphological studies based on cranial postcranial and soft tissue anatomy (Horovitz and Sanchezmiddot Villagra 2003) indicilte that Paucituberculata is the sister group of Australidelphia

Microbi otherialls and pallci tuberculatans are poorly represented in presenlday ecosyste ms (Flores 2006a b PatterSon 2007 Patterson and Rogers 2007) The only extant microbiotherian is the so-called monito del mome (Dromiciops gliroides) a small insectivorous marsupial endemic to the temperate forests of southern Chi Ie and Argentina associated wi th (he southern beech forests (Nothofagus) and South American mountain bamboos (Chusquea) (Hershkovitz 1999) Dromiciops gLiroides is lhe only South American marsupial reported to exhibit deep torpor or hibemation (Greer 1966 Bozinovic el a l 2004) In the summer season this species is active during the night being a common mammal of the understory stratum (Rodriguez-Cabal et al 2008)

The living Paucituberculata include five species that are grouped in the genera Caenoestes Lestoros and RhYllcholestes all belonging 10 Caenolestidae (shrew oppomiddot sum s) This clade has a disjunct Andean distribution that ranges from Venezuela Lo northern Pem (Caenolestes Albuja and Patterson 1996) central Pem and Bolivia (ustoros inca Anderson 1997 Ramirez er ol 2(07) and southern Chile and Argen tina (Rhyncholestes Patterson and Gallardo 1987 Birney et aI 1996) Caeno1estids have a wide latitudinal and al tirudinal (up to 4000 meters above sea level) distribution spanning several biomes including Paramo Montane foresl and Valdi vian forest Extant caenoshyIelttids are small shrewmiddotsized marsupials which inhabit moist and dense vegetated microhabitaLs (Kirsh and WaJler 1979 Kelt el al 1994) The scanty ecological data reported in the literature indicate that caenolestids have a cursorial-leaping locomotion and a plimarily insecti vorous diet (Kirsh and Waller 1979 Barkley and Whitaker 1984 Patterson and GaiJardo 1987 Patterson 2007)

1l1e fossiJ record of Paucitubercula[a and M icrobiotheria indicates that these marsupials had a wider geographic disllibution and higher taxonomic diversity than those of the present (Abell o 2007 G01n ef al in press) The oldestmiddot known Paucituberculata and Microbiotheria date from the Paleocene and include fonns such as the paucituberculatan Bardalestes Goin Candela Abello and Oli veira 2009 (ltabora ian Age Argentina Goin el a l in press) and the microbiotherian Mirandarheriw71 (Paula Couto 1952) from Brazil (Itaboraian Age Goin e( al in press) Bolh groups achieved their hi ghes t taxonomic di versity in the Early Mi ocene Colhuehuapian ~nd Santacrucian Ages but the infened cladogenetic events that gave rise to the Miocene fOims seem to have OCC UlTed during the Oligocene (Abello 2007 Goin el al 2010) By the Early Miocene microshybiotherians are represented by nine species belonging to Microbiotheriidae At [he same time paucituberculatans are represented for 23 species gro uped among Caenolestjshydae Pichipilidae Palaeothentidae and Abderitidae

Despite the abundant representation of small marsupials (particularly paucituberculatans) in the Early Miocene (Bown nd Fleagle 1993 Abello 2007) they are mainly known by mandibular and maxillalY remains and isolated leeth Consequently the reconstructions of cerrain paleoshyecological aspects (eg_ body size diet) have been de rived from the sLud y of dental remains

Several ecological niches have been identified among Paucituberculala (Dumont el 01 2(00) small insectivores (Caenolestidae and Pichipilic1ae) small middot to medium-size inseclivore- fru givores (Palaeotbentidae) and small- to mediummiddotsize frugivores (AbdeliLidae) As yet only two specimiddot mens including postcrartial and cranial rem ains are reported for Pancituberculata (Abello and Candela 2010) These were referred (0 two palaeothentid species Palaeothentes minurus Ameghino L887 and Paloeolhentes lemoinei Ameghino 1887 from the late Early Miocene (Santa Cruz Fonnation) Curso-saltatorial locomotor srrategies were inferred for both species (Abello and Candela 20 I 0)

In this chapter we summarize previous paleoecological studies of Sanlacrucian Paucituberculala and present the results of a new paleoecological analysis of Santacrllcian Microbiotheria Additionally we evaluate the paleoenvironshymental significance of non-carnivorous Miocene marsupials

102 Santacrucian pattcituberculatans and microbiotherians

During the South American Miocene paucituberculatans and microbiotherians coexisted with other metalhelians such as Sparassodonta polydolopimorphian Argyrolagoidea and Didelphimorphia Paucituberculatans occur in most Miocene assemblages but Argyrolagidae and Didelphimorphia are rare or absent as is tbe c15e for the late Early Miocene fauna of Santa

158 Mana Aleiandra Abello e t al

a

b

e

n

Fig 102 De ntition of se lec ted Pauciluberculala and Microbiotheriidae species or the Sama Cruz Formation a b MicrohiolherillrJ acicIIlcl (MACN-A 5727) left mandibula r fragmen with 1111-4 in labial (a) and occlusal (b) views c d MicrohiothenllfJ1 gallegosll1se (Lype AMNH 9591) right mandibular fragment wilh p3- rn3 in lab ial (c) and occlusal (eI) views e f Stifotherium dissimile ([ype MACNmiddotA 8464) right mandibular fragme nt wit h i2 i3 a lveoJous three one-roOfed teeth and p2-m4 in labial (e) and occlusal (f) views g h PhOllocdromlls gacilis (lype MACN-A 8457) left mandibular fragment with p3-m3 in labial (g) and occlusal (h) views i j Palaeolhenfes minutllS (MACN-A 5591-5518a) right malldibular fragme nt wilh p3- m4 in labial (i) and occlusal (j) views k) Acdesfil owenii (type 11ACN~A 1379) mandibular fragment wi th i2 fonr a lveoli of onemiddotrooted teeth complete p3-m 1 and m2 trigonid in labial (k) and occJugtal (I) views In n Abderites meridionalis (01) (MLP 55middot XIlmiddot13-145) mandibular fragment wilh iI four alveolous of onemiddotrooled teeth and p3- 01 1 in labia l view (n) (Lype MACNmiddotA 12) mandibular fra gment with T)lI - 3 and m4 alveolous in occlusal view Scale bar 2 mm

Cruz beds To date microbio theri ans (Fig 102a- d) and paucituberculatan s (Figs lO2e- n and 103) are the only non-carnivorous merarheria ns recorded in rhe Santa Cmz Formation Metarherian s of this formation were first described by Ameghino (1887 1891) Sinc lair ( 1906) and Marshall (1976a 1980 1982) made significant contribushytions to the knowledge of the di versity of Sa nfacruc ian pauc irubercularans and mic robiolheriids Recent revisions include those of Bown and Fleagle ( 1993) Tauber (1997) Abe llo (2007) and Abello and Rlibilar-Rogers (in press) An updated taxonom ic list and the records of pauc itubershyculalans and microbiothe riids from localities of the Santa Cru z Formation are presented in Appendix 10 1

103 Materials and methods

The mareJia l studied is li sted in Append ix 102

1031 Abbeviations The generalized metatherian dental formula is IIi 54 Cc 11 Pip 33 Mm 44

Institutional abbreviations MACN Museo Argentino de Ciencias Naturales B Rivadavia Buenos Aires Argenrina MACN-A Colecci6n Nacional Ameghino

MLP Museo de La Plata La Plata Argentina AMNH American Museum of Natural History New

York EEUU MPM-PY Museo Regional Provinc ial Padre Manuel

Jesus Molina RIO Gallegos Argentina

1032 Melbodology To estimate body masses and infer dietary prete rences of SantacllJc ian non -camivorous marsupials we fo llow the methodologies of Dumont er al (2000) In (he context of an analysis of dietary preferences of Pauciruberculta Dumont el al (2000) studied all available Santacrucian species Here we summari ze the results of these dietary reconstructions and apply the same rnethcxlalogy to [he Sancac[1Jcian Micro shybiotheriidae In contrast to Dumont et al (2000) we follov Abello and Rubilar-Rogers (in press) in considering A merdionalis Ameghino 1887 La be a different specie 5i from the Colhuehuapian Ahderitemiddot crisplls Ameghina 1902

159 Paleoecology of Santacrucian Paucituberculata and Microbiofheria

Ru

b

Ft

f

Tt

m

k n

d

It

9 Mm

Latf

ff~ Anf

Fig 103 Postcranial skeleton of Paaeothentcs species Paacofhenres minutus a b right humerus (MACN-A 56 I 9-5639c) in anterior (a) and posterior (b) views c d right ulna (MACN-A 5619-563ge) in lateral (c) and anterior (d) views e f Right radius (MACN-A 56 I 9-5639d) in proximal (e) and medial (f) views g Pelvis (MACN-A 5619-5639f) in lateral view h right femur (MACN-A 56 I 9-5639g) in anterior view i left femur (MACN-A 5619-5639h) in anterior view PaaeOlhelltes emoinei (MPM-PV 3494) j k left tibia in anterior U) and lateral (k) views I right tibia in distal view m right asrragalus in dorsal view PaiaeOlhenies minUius (MACN-A 5619-5639i) n right calcaneum in dorsal view Scale bar 4 mm Abbreviations A acetabulum Aff astragalofibular facet Auf astragalouavicular facet Atc anterIor tibial crest Bt bicipital tuberosity C capitulum Cacud cuboid facet distal half Dc delLopectoral crest Ef ectal facet Ft femoral tubercle Gt great trochanter It ischial tuberosity Latf lateral astragalmibial facet Lec lateral epicondylar crest Lt lesser trochanter Matf medial astragalotibial facet Me medial epicondyle Mm medial mallcolus Of olecranon fossa Op olecranon process Pt peroneal tubercle Pte proximal trochlear crest Raf radial articular faceL for the capitulum Ru radio-ulnar facet Sc supracondyloid crest Sfa sustentacular facet Sfo supracondyloid foramen Srf supratrochlear foramen T trochlea Tn trochlear notch Tpe ribial posterior extension Tl third trochanLer

160 M ara Alejandra Ahello el al

Regarding the locomotor habits of Palaevchentes species we present here a synthesis of Abello and Candelas (2010) main results

Body mass Body masses were esrimated from the occlusal area (mesiodisLal length x labiolinguaJ breadth)

of the second lower molar using the linear regress ion equation

In bod y mass = 24 19 + ( 1727 x In 111 2 area) (Eq 101)

deri ved by Dumont el al (2000) for li ving marsupials T his equation included 27 extant marsupial species whose body masses range from approximately 10 10 1500g ltI wide range encompass ing that of Sanl3cI1Jcian marsupia ls

Locomotion and use of the substrate To assess the locoshymotor strategies of Palaeohemes minutus and P emoinei A bello and Candela (2010) performed a 1ll0lJgthofunct ionai analysis based on comparisons with living South American marsupials

PalaeOlhenles minUlus (MACN-A 56 19- 5639a-i) is the most iUlportant specimen available being represented by the humeros radius ulna femur pelvis and calcaneum (Fig lOJa- i n) The postcranium of P lemoinei (MPM-PY 3494) preserves the hurnenJs ulna pelvis tibiae and astragshyalus (Fig 1O3j-m) The postcranial features with functional significance preserved in these fossils were compared to those or extant marsupials having various locomotor behavshyiors Abell o and Candela (2010) evaluated uai ts functionally related to different movements (eg flexionextension promlshytionsupination) In this context special attention was paid in the analysis of articular surfaces (eg elbow cmroastragalar and hip joints) and areas of muscular attachment Cuelloestes fuiiginoslls and the dideJphids Melaczrus l1udicoudotus and

MOl1udelphis dimidiota were considered as lerrestriaJ model species The didelphid Didelphis Giilita and the microbiothershyjid Dromiciops gliroides were included as scansoriaJ and arboreal mode ls respectively

Feeding habits The dietary habits of the Santacrucian microbio theliids were investiga ted following the method of die tary reconstructions proposed by Stra it (1 993a b) Thjs approach relies on the assumption that tJle developshyment of sheariug crests on [he molars should reflecr the physical properties of [he foods lhat must be comminu ted (Strait 1993b Kay and Hylander 1978)

Two molar shearing ratios are calculated to discriminate frugivorous from faunivorous small-bodied taxa in a comshyparative framework with extant mammals whose dietary preferences are well known Both ratios consider the sum of six shearing crests (cres ts 1--6 of Kay and Hiiemae 1974 Fig 104) and two size surrogates m2 length and the square root of m2 area The shearing ratio based on area

Labial

L Anterior

Fig lOA Occlusal view of lert lower second molar showing lhe shearing cresls 1-6 (Kay and Hiiemac 1974) measured in Ihi s study

(SRA) is the SUul or length or crests l-u divided by the square root of tooth area ilnd the shearing ratio based on length (SRL) is the sum of lengths of cres ts I-u divided by molar length

The present ana lysis is based on those performed by Dumont el al (2000) for paucituberculatans who included the following living marsupials as models four insectivores (the p~lU cituberc ulltltans Lestoros inca and CoenoLesles canivenfer the dasyurids Antechinus stuartii and Sminf7opsis crassicClldata) and I-wo frugivores (the petaurids PetalfilS brevceps and Acrohates py~maeus) To broaden the compararive sample of extant marsupials we inclu ded here the in sec ti vorous microbiotheriid Dromishyciopt gliroides (Patterson and Rogers 2007 and references there in)

Living marsupials especially those of fh e Australasian region have a broad dietary d iversity including a wide range of (ood suc h as verte brate and invertebrate prey vegetat ive and reproducti ve ti ssues of plants plam ex udshyates and fungi (Hume 2006) For the living marsupials several feedin g categories may be established (Lee and COCkburn (985) however the definition of strict trophic categories is imprecise (Vie ira and Astu ltl de Momes 2003) Taking into account this constraint we have followed DUnlont el al (2000) and used broad dietary ca tegor ies to infer the die t of the Santacnlc ian marsupials lllese authors used two ca tegories faunivores and frugivores but we have preferred to use insec ti vores instead of faunivores for two reasons (I) faunivores is an equivocal term because it has been used to refer to those ca rnivorous mammals thai ea t ven ebrate (eg Hume 2003) as well as to those thar eat invertebrate (eg Heesy 2008) and (2) all the living species used by Dumont eT al (2000) to represent faunishyvores are acrualJy insec tivores (= insectivoreomnivore of Lee and Cockburn 1985) because they reed primarily on arthropods (whicb may be consumed as adu lts or juvenile stages) but thei r die t may include in some cases vegetable

158 Mana Aleiandra Abello e t al

a

b

e

n

Fig 102 De ntition of se lec ted Pauciluberculala and Microbiotheriidae species or the Sama Cruz Formation a b MicrohiolherillrJ acicIIlcl (MACN-A 5727) left mandibula r fragmen with 1111-4 in labial (a) and occlusal (b) views c d MicrohiothenllfJ1 gallegosll1se (Lype AMNH 9591) right mandibular fragment wilh p3- rn3 in lab ial (c) and occlusal (eI) views e f Stifotherium dissimile ([ype MACNmiddotA 8464) right mandibular fragme nt wit h i2 i3 a lveoJous three one-roOfed teeth and p2-m4 in labial (e) and occlusal (f) views g h PhOllocdromlls gacilis (lype MACN-A 8457) left mandibular fragment with p3-m3 in labial (g) and occlusal (h) views i j Palaeolhenfes minutllS (MACN-A 5591-5518a) right malldibular fragme nt wilh p3- m4 in labial (i) and occlusal (j) views k) Acdesfil owenii (type 11ACN~A 1379) mandibular fragment wi th i2 fonr a lveoli of onemiddotrooted teeth complete p3-m 1 and m2 trigonid in labial (k) and occJugtal (I) views In n Abderites meridionalis (01) (MLP 55middot XIlmiddot13-145) mandibular fragment wilh iI four alveolous of onemiddotrooled teeth and p3- 01 1 in labia l view (n) (Lype MACNmiddotA 12) mandibular fra gment with T)lI - 3 and m4 alveolous in occlusal view Scale bar 2 mm

Cruz beds To date microbio theri ans (Fig 102a- d) and paucituberculatan s (Figs lO2e- n and 103) are the only non-carnivorous merarheria ns recorded in rhe Santa Cmz Formation Metarherian s of this formation were first described by Ameghino (1887 1891) Sinc lair ( 1906) and Marshall (1976a 1980 1982) made significant contribushytions to the knowledge of the di versity of Sa nfacruc ian pauc irubercularans and mic robiolheriids Recent revisions include those of Bown and Fleagle ( 1993) Tauber (1997) Abe llo (2007) and Abello and Rlibilar-Rogers (in press) An updated taxonom ic list and the records of pauc itubershyculalans and microbiothe riids from localities of the Santa Cru z Formation are presented in Appendix 10 1

103 Materials and methods

The mareJia l studied is li sted in Append ix 102

1031 Abbeviations The generalized metatherian dental formula is IIi 54 Cc 11 Pip 33 Mm 44

Institutional abbreviations MACN Museo Argentino de Ciencias Naturales B Rivadavia Buenos Aires Argenrina MACN-A Colecci6n Nacional Ameghino

MLP Museo de La Plata La Plata Argentina AMNH American Museum of Natural History New

York EEUU MPM-PY Museo Regional Provinc ial Padre Manuel

Jesus Molina RIO Gallegos Argentina

1032 Melbodology To estimate body masses and infer dietary prete rences of SantacllJc ian non -camivorous marsupials we fo llow the methodologies of Dumont er al (2000) In (he context of an analysis of dietary preferences of Pauciruberculta Dumont el al (2000) studied all available Santacrucian species Here we summari ze the results of these dietary reconstructions and apply the same rnethcxlalogy to [he Sancac[1Jcian Micro shybiotheriidae In contrast to Dumont et al (2000) we follov Abello and Rubilar-Rogers (in press) in considering A merdionalis Ameghino 1887 La be a different specie 5i from the Colhuehuapian Ahderitemiddot crisplls Ameghina 1902

159 Paleoecology of Santacrucian Paucituberculata and Microbiofheria

Ru

b

Ft

f

Tt

m

k n

d

It

9 Mm

Latf

ff~ Anf

Fig 103 Postcranial skeleton of Paaeothentcs species Paacofhenres minutus a b right humerus (MACN-A 56 I 9-5639c) in anterior (a) and posterior (b) views c d right ulna (MACN-A 5619-563ge) in lateral (c) and anterior (d) views e f Right radius (MACN-A 56 I 9-5639d) in proximal (e) and medial (f) views g Pelvis (MACN-A 5619-5639f) in lateral view h right femur (MACN-A 56 I 9-5639g) in anterior view i left femur (MACN-A 5619-5639h) in anterior view PaaeOlhelltes emoinei (MPM-PV 3494) j k left tibia in anterior U) and lateral (k) views I right tibia in distal view m right asrragalus in dorsal view PaiaeOlhenies minUius (MACN-A 5619-5639i) n right calcaneum in dorsal view Scale bar 4 mm Abbreviations A acetabulum Aff astragalofibular facet Auf astragalouavicular facet Atc anterIor tibial crest Bt bicipital tuberosity C capitulum Cacud cuboid facet distal half Dc delLopectoral crest Ef ectal facet Ft femoral tubercle Gt great trochanter It ischial tuberosity Latf lateral astragalmibial facet Lec lateral epicondylar crest Lt lesser trochanter Matf medial astragalotibial facet Me medial epicondyle Mm medial mallcolus Of olecranon fossa Op olecranon process Pt peroneal tubercle Pte proximal trochlear crest Raf radial articular faceL for the capitulum Ru radio-ulnar facet Sc supracondyloid crest Sfa sustentacular facet Sfo supracondyloid foramen Srf supratrochlear foramen T trochlea Tn trochlear notch Tpe ribial posterior extension Tl third trochanLer

160 M ara Alejandra Ahello el al

Regarding the locomotor habits of Palaevchentes species we present here a synthesis of Abello and Candelas (2010) main results

Body mass Body masses were esrimated from the occlusal area (mesiodisLal length x labiolinguaJ breadth)

of the second lower molar using the linear regress ion equation

In bod y mass = 24 19 + ( 1727 x In 111 2 area) (Eq 101)

deri ved by Dumont el al (2000) for li ving marsupials T his equation included 27 extant marsupial species whose body masses range from approximately 10 10 1500g ltI wide range encompass ing that of Sanl3cI1Jcian marsupia ls

Locomotion and use of the substrate To assess the locoshymotor strategies of Palaeohemes minutus and P emoinei A bello and Candela (2010) performed a 1ll0lJgthofunct ionai analysis based on comparisons with living South American marsupials

PalaeOlhenles minUlus (MACN-A 56 19- 5639a-i) is the most iUlportant specimen available being represented by the humeros radius ulna femur pelvis and calcaneum (Fig lOJa- i n) The postcranium of P lemoinei (MPM-PY 3494) preserves the hurnenJs ulna pelvis tibiae and astragshyalus (Fig 1O3j-m) The postcranial features with functional significance preserved in these fossils were compared to those or extant marsupials having various locomotor behavshyiors Abell o and Candela (2010) evaluated uai ts functionally related to different movements (eg flexionextension promlshytionsupination) In this context special attention was paid in the analysis of articular surfaces (eg elbow cmroastragalar and hip joints) and areas of muscular attachment Cuelloestes fuiiginoslls and the dideJphids Melaczrus l1udicoudotus and

MOl1udelphis dimidiota were considered as lerrestriaJ model species The didelphid Didelphis Giilita and the microbiothershyjid Dromiciops gliroides were included as scansoriaJ and arboreal mode ls respectively

Feeding habits The dietary habits of the Santacrucian microbio theliids were investiga ted following the method of die tary reconstructions proposed by Stra it (1 993a b) Thjs approach relies on the assumption that tJle developshyment of sheariug crests on [he molars should reflecr the physical properties of [he foods lhat must be comminu ted (Strait 1993b Kay and Hylander 1978)

Two molar shearing ratios are calculated to discriminate frugivorous from faunivorous small-bodied taxa in a comshyparative framework with extant mammals whose dietary preferences are well known Both ratios consider the sum of six shearing crests (cres ts 1--6 of Kay and Hiiemae 1974 Fig 104) and two size surrogates m2 length and the square root of m2 area The shearing ratio based on area

Labial

L Anterior

Fig lOA Occlusal view of lert lower second molar showing lhe shearing cresls 1-6 (Kay and Hiiemac 1974) measured in Ihi s study

(SRA) is the SUul or length or crests l-u divided by the square root of tooth area ilnd the shearing ratio based on length (SRL) is the sum of lengths of cres ts I-u divided by molar length

The present ana lysis is based on those performed by Dumont el al (2000) for paucituberculatans who included the following living marsupials as models four insectivores (the p~lU cituberc ulltltans Lestoros inca and CoenoLesles canivenfer the dasyurids Antechinus stuartii and Sminf7opsis crassicClldata) and I-wo frugivores (the petaurids PetalfilS brevceps and Acrohates py~maeus) To broaden the compararive sample of extant marsupials we inclu ded here the in sec ti vorous microbiotheriid Dromishyciopt gliroides (Patterson and Rogers 2007 and references there in)

Living marsupials especially those of fh e Australasian region have a broad dietary d iversity including a wide range of (ood suc h as verte brate and invertebrate prey vegetat ive and reproducti ve ti ssues of plants plam ex udshyates and fungi (Hume 2006) For the living marsupials several feedin g categories may be established (Lee and COCkburn (985) however the definition of strict trophic categories is imprecise (Vie ira and Astu ltl de Momes 2003) Taking into account this constraint we have followed DUnlont el al (2000) and used broad dietary ca tegor ies to infer the die t of the Santacnlc ian marsupials lllese authors used two ca tegories faunivores and frugivores but we have preferred to use insec ti vores instead of faunivores for two reasons (I) faunivores is an equivocal term because it has been used to refer to those ca rnivorous mammals thai ea t ven ebrate (eg Hume 2003) as well as to those thar eat invertebrate (eg Heesy 2008) and (2) all the living species used by Dumont eT al (2000) to represent faunishyvores are acrualJy insec tivores (= insectivoreomnivore of Lee and Cockburn 1985) because they reed primarily on arthropods (whicb may be consumed as adu lts or juvenile stages) but thei r die t may include in some cases vegetable

159 Paleoecology of Santacrucian Paucituberculata and Microbiofheria

Ru

b

Ft

f

Tt

m

k n

d

It

9 Mm

Latf

ff~ Anf

Fig 103 Postcranial skeleton of Paaeothentcs species Paacofhenres minutus a b right humerus (MACN-A 56 I 9-5639c) in anterior (a) and posterior (b) views c d right ulna (MACN-A 5619-563ge) in lateral (c) and anterior (d) views e f Right radius (MACN-A 56 I 9-5639d) in proximal (e) and medial (f) views g Pelvis (MACN-A 5619-5639f) in lateral view h right femur (MACN-A 56 I 9-5639g) in anterior view i left femur (MACN-A 5619-5639h) in anterior view PaaeOlhelltes emoinei (MPM-PV 3494) j k left tibia in anterior U) and lateral (k) views I right tibia in distal view m right asrragalus in dorsal view PaiaeOlhenies minUius (MACN-A 5619-5639i) n right calcaneum in dorsal view Scale bar 4 mm Abbreviations A acetabulum Aff astragalofibular facet Auf astragalouavicular facet Atc anterIor tibial crest Bt bicipital tuberosity C capitulum Cacud cuboid facet distal half Dc delLopectoral crest Ef ectal facet Ft femoral tubercle Gt great trochanter It ischial tuberosity Latf lateral astragalmibial facet Lec lateral epicondylar crest Lt lesser trochanter Matf medial astragalotibial facet Me medial epicondyle Mm medial mallcolus Of olecranon fossa Op olecranon process Pt peroneal tubercle Pte proximal trochlear crest Raf radial articular faceL for the capitulum Ru radio-ulnar facet Sc supracondyloid crest Sfa sustentacular facet Sfo supracondyloid foramen Srf supratrochlear foramen T trochlea Tn trochlear notch Tpe ribial posterior extension Tl third trochanLer

160 M ara Alejandra Ahello el al

Regarding the locomotor habits of Palaevchentes species we present here a synthesis of Abello and Candelas (2010) main results

Body mass Body masses were esrimated from the occlusal area (mesiodisLal length x labiolinguaJ breadth)

of the second lower molar using the linear regress ion equation

In bod y mass = 24 19 + ( 1727 x In 111 2 area) (Eq 101)

deri ved by Dumont el al (2000) for li ving marsupials T his equation included 27 extant marsupial species whose body masses range from approximately 10 10 1500g ltI wide range encompass ing that of Sanl3cI1Jcian marsupia ls

Locomotion and use of the substrate To assess the locoshymotor strategies of Palaeohemes minutus and P emoinei A bello and Candela (2010) performed a 1ll0lJgthofunct ionai analysis based on comparisons with living South American marsupials

PalaeOlhenles minUlus (MACN-A 56 19- 5639a-i) is the most iUlportant specimen available being represented by the humeros radius ulna femur pelvis and calcaneum (Fig lOJa- i n) The postcranium of P lemoinei (MPM-PY 3494) preserves the hurnenJs ulna pelvis tibiae and astragshyalus (Fig 1O3j-m) The postcranial features with functional significance preserved in these fossils were compared to those or extant marsupials having various locomotor behavshyiors Abell o and Candela (2010) evaluated uai ts functionally related to different movements (eg flexionextension promlshytionsupination) In this context special attention was paid in the analysis of articular surfaces (eg elbow cmroastragalar and hip joints) and areas of muscular attachment Cuelloestes fuiiginoslls and the dideJphids Melaczrus l1udicoudotus and

MOl1udelphis dimidiota were considered as lerrestriaJ model species The didelphid Didelphis Giilita and the microbiothershyjid Dromiciops gliroides were included as scansoriaJ and arboreal mode ls respectively

Feeding habits The dietary habits of the Santacrucian microbio theliids were investiga ted following the method of die tary reconstructions proposed by Stra it (1 993a b) Thjs approach relies on the assumption that tJle developshyment of sheariug crests on [he molars should reflecr the physical properties of [he foods lhat must be comminu ted (Strait 1993b Kay and Hylander 1978)

Two molar shearing ratios are calculated to discriminate frugivorous from faunivorous small-bodied taxa in a comshyparative framework with extant mammals whose dietary preferences are well known Both ratios consider the sum of six shearing crests (cres ts 1--6 of Kay and Hiiemae 1974 Fig 104) and two size surrogates m2 length and the square root of m2 area The shearing ratio based on area

Labial

L Anterior

Fig lOA Occlusal view of lert lower second molar showing lhe shearing cresls 1-6 (Kay and Hiiemac 1974) measured in Ihi s study

(SRA) is the SUul or length or crests l-u divided by the square root of tooth area ilnd the shearing ratio based on length (SRL) is the sum of lengths of cres ts I-u divided by molar length

The present ana lysis is based on those performed by Dumont el al (2000) for paucituberculatans who included the following living marsupials as models four insectivores (the p~lU cituberc ulltltans Lestoros inca and CoenoLesles canivenfer the dasyurids Antechinus stuartii and Sminf7opsis crassicClldata) and I-wo frugivores (the petaurids PetalfilS brevceps and Acrohates py~maeus) To broaden the compararive sample of extant marsupials we inclu ded here the in sec ti vorous microbiotheriid Dromishyciopt gliroides (Patterson and Rogers 2007 and references there in)

Living marsupials especially those of fh e Australasian region have a broad dietary d iversity including a wide range of (ood suc h as verte brate and invertebrate prey vegetat ive and reproducti ve ti ssues of plants plam ex udshyates and fungi (Hume 2006) For the living marsupials several feedin g categories may be established (Lee and COCkburn (985) however the definition of strict trophic categories is imprecise (Vie ira and Astu ltl de Momes 2003) Taking into account this constraint we have followed DUnlont el al (2000) and used broad dietary ca tegor ies to infer the die t of the Santacnlc ian marsupials lllese authors used two ca tegories faunivores and frugivores but we have preferred to use insec ti vores instead of faunivores for two reasons (I) faunivores is an equivocal term because it has been used to refer to those ca rnivorous mammals thai ea t ven ebrate (eg Hume 2003) as well as to those thar eat invertebrate (eg Heesy 2008) and (2) all the living species used by Dumont eT al (2000) to represent faunishyvores are acrualJy insec tivores (= insectivoreomnivore of Lee and Cockburn 1985) because they reed primarily on arthropods (whicb may be consumed as adu lts or juvenile stages) but thei r die t may include in some cases vegetable

160 M ara Alejandra Ahello el al

Regarding the locomotor habits of Palaevchentes species we present here a synthesis of Abello and Candelas (2010) main results

Body mass Body masses were esrimated from the occlusal area (mesiodisLal length x labiolinguaJ breadth)

of the second lower molar using the linear regress ion equation

In bod y mass = 24 19 + ( 1727 x In 111 2 area) (Eq 101)

deri ved by Dumont el al (2000) for li ving marsupials T his equation included 27 extant marsupial species whose body masses range from approximately 10 10 1500g ltI wide range encompass ing that of Sanl3cI1Jcian marsupia ls

Locomotion and use of the substrate To assess the locoshymotor strategies of Palaeohemes minutus and P emoinei A bello and Candela (2010) performed a 1ll0lJgthofunct ionai analysis based on comparisons with living South American marsupials

PalaeOlhenles minUlus (MACN-A 56 19- 5639a-i) is the most iUlportant specimen available being represented by the humeros radius ulna femur pelvis and calcaneum (Fig lOJa- i n) The postcranium of P lemoinei (MPM-PY 3494) preserves the hurnenJs ulna pelvis tibiae and astragshyalus (Fig 1O3j-m) The postcranial features with functional significance preserved in these fossils were compared to those or extant marsupials having various locomotor behavshyiors Abell o and Candela (2010) evaluated uai ts functionally related to different movements (eg flexionextension promlshytionsupination) In this context special attention was paid in the analysis of articular surfaces (eg elbow cmroastragalar and hip joints) and areas of muscular attachment Cuelloestes fuiiginoslls and the dideJphids Melaczrus l1udicoudotus and

MOl1udelphis dimidiota were considered as lerrestriaJ model species The didelphid Didelphis Giilita and the microbiothershyjid Dromiciops gliroides were included as scansoriaJ and arboreal mode ls respectively

Feeding habits The dietary habits of the Santacrucian microbio theliids were investiga ted following the method of die tary reconstructions proposed by Stra it (1 993a b) Thjs approach relies on the assumption that tJle developshyment of sheariug crests on [he molars should reflecr the physical properties of [he foods lhat must be comminu ted (Strait 1993b Kay and Hylander 1978)

Two molar shearing ratios are calculated to discriminate frugivorous from faunivorous small-bodied taxa in a comshyparative framework with extant mammals whose dietary preferences are well known Both ratios consider the sum of six shearing crests (cres ts 1--6 of Kay and Hiiemae 1974 Fig 104) and two size surrogates m2 length and the square root of m2 area The shearing ratio based on area

Labial

L Anterior

Fig lOA Occlusal view of lert lower second molar showing lhe shearing cresls 1-6 (Kay and Hiiemac 1974) measured in Ihi s study

(SRA) is the SUul or length or crests l-u divided by the square root of tooth area ilnd the shearing ratio based on length (SRL) is the sum of lengths of cres ts I-u divided by molar length

The present ana lysis is based on those performed by Dumont el al (2000) for paucituberculatans who included the following living marsupials as models four insectivores (the p~lU cituberc ulltltans Lestoros inca and CoenoLesles canivenfer the dasyurids Antechinus stuartii and Sminf7opsis crassicClldata) and I-wo frugivores (the petaurids PetalfilS brevceps and Acrohates py~maeus) To broaden the compararive sample of extant marsupials we inclu ded here the in sec ti vorous microbiotheriid Dromishyciopt gliroides (Patterson and Rogers 2007 and references there in)

Living marsupials especially those of fh e Australasian region have a broad dietary d iversity including a wide range of (ood suc h as verte brate and invertebrate prey vegetat ive and reproducti ve ti ssues of plants plam ex udshyates and fungi (Hume 2006) For the living marsupials several feedin g categories may be established (Lee and COCkburn (985) however the definition of strict trophic categories is imprecise (Vie ira and Astu ltl de Momes 2003) Taking into account this constraint we have followed DUnlont el al (2000) and used broad dietary ca tegor ies to infer the die t of the Santacnlc ian marsupials lllese authors used two ca tegories faunivores and frugivores but we have preferred to use insec ti vores instead of faunivores for two reasons (I) faunivores is an equivocal term because it has been used to refer to those ca rnivorous mammals thai ea t ven ebrate (eg Hume 2003) as well as to those thar eat invertebrate (eg Heesy 2008) and (2) all the living species used by Dumont eT al (2000) to represent faunishyvores are acrualJy insec tivores (= insectivoreomnivore of Lee and Cockburn 1985) because they reed primarily on arthropods (whicb may be consumed as adu lts or juvenile stages) but thei r die t may include in some cases vegetable

Paleoecology of Santacrucion Pau6 tuherculata and Microhiotheria L6J

maHer and fungi On the other hand the marsupials used by Dumon t el 01 (2000) to represent frugivores feed mainly on plant materia ls such as nectar pollen exudates (gum sap and sugar encrusrations produced by sap-sucking insects and known as manna) and fruirs but their diet may be complemented with insects when seasonally available In thi s context this category includes those exudate feeders insectivores and frugivoreso mnivores of Lee and Cockbum (1985) Finally Dumont et al (2000) also found a third feeding category (ie mixed feeders or frugivorous- faushynivorous) fonned by rhose marsupials that emerge as fmgivorous or faunivorous depending on shearing ratio (i e the caenolestid SlilOlherium dissimile Amegino 1887 the abderitid Pitheculites minimlls Ameghino 1902 and (he palaeorhentid Acdestis lemairei Bown and Fleagle 1993) We prefe r to use inseclivore-frugivore because both mixed feeders and frugivorous-fauni vorous are ambigushyous renns The former is more frequently used 10 designale those herbivorous mammals that are intermediate between grazers and browsers ealing bOlh browse and grass (eg the red deer Cervl s eLaphus the impala Aepyceros melampllS tJle nyaJa Trageaphus ongasi Staver ef of 2009) The

difficulty with the latter is the ambiguity in the usage of fau nivore as explained above

Measurements of lower second molar maximum length maxi muln width and the lengths of six of its shearing cres ts were made on a Carl Zeiss Microscope using a measureshyment module (Axiovision 42 and 46)

104 Results

1041 Body mass The estimated body masses were 20 g for MicrobiOlherium acicufa 40 g for M palagonicurn 61 g for M leIwechum 147 g for M galiegasellSe and 487 g for Abderites meridionalis Table IOl shows the current body mass estimashyLions for microbiotherians and A meridionalis and those previshyously presented by Dumont et al (2000) for pauciuberculaans with the exception of A meridionalis (see Methodology)

1042 Locomotion and use of substrate The results of comparative analysis with extant marsupials showed that several postcranial features of Potaeoritenres species resemble those of modern curso-saltatorial fomls

Table 101 Body mass es timates and diet of Santacrucian M icrobiotheriidae and Paucituberclllata

Sample size m2 area (mm 2) Body mass Diet

Microbiotheria Microbiolheriidae Microbiolherium acicflla 138 20 g [nsectivorous M icrobiorherium patagolliCLlJl1 207 40g Insecti vorous Microbiorherium fehuelchum 266 6 1 g Insectivorous M icrobiofherilln galegoSeJ1se 444 147 g I nsecti vorous- frugivorous Paucituberculata Caenolesrid ae SliLOlheriurn dissimile 3 148 37 g In secti vo rou s- frug i vorous Pichipilidae Phonocdromus gracilis 2 104 28 g lnsecti vorou s PalaeO lhentidae PaacOlhentes aratae 13 1134 860 g Frugivorous Paiaeorhellles minuus 112 306 82 g Insecrivorou s Paacorhclues internedius 30 467 192 g Insec ri vorous Paaeori1etlfes lemoinei 28 718 425 g Insectivorous PaiaeOlhellles pasuali 6 225 38 g Insecti vorous Acdeslis owenpound II3 67 1 344g Frugivorous Acdesis Icmairei 18 S 13 256 g Insecti vorous-fiu gi vorous Abderilidae Abderi les meridpoundonalis IS 886 487 g Frugivorous

The sample size and mean m2 area (mm2) from which the body mass was reconstructed are presented Inferred diet (Die t) is

based on shearing rat io and body mass data

162

such as CQenolestesfuliginosus and Metachirus nudicaudalus (Abello and Candela 2010) Characteristics of the forelimbs include among other features a deep and high humeral trochlea (Fig 103a) a deep olecranon fossa (Fig JO3b) and mediolaterally broad proximal trochlear crest (Fig lO3c d) These featmes indicate a well-stabilized elbow joint The short lateral epicondylar crest (Fig 103b) and the suboval radial head (Fig lO3e) suggest that pronation-supinshyation was limited (Abello and Candela 2010 1520) The pelvis better preserved in P minutus shows a restrictive acetabulum (ie tightly articulating Szalay and Sargis 2001) lengthened ischium and prominent femoral tubercle as well as ischial ruberosity (Fig 1O3g) The morphology of the pelvis indicates a high stability at the ilio-femoral joint and an increased mechanical advantage of the flexors and extensors of the hip (ie rectus femoris and hamstring muscles) which are well developed in saltatorial species (Argot 2003a) The greater trochanter of the femur projects beyond the proximal surface of the femoral head (Fig 103i) indicating that the gluteal muscles were favorably positioned to produce fast extension at the hip joint as occms in agile and leaping species Additionally the hind limbs of Palaeothentes species like those of curso-saltatorial f0I111s have features associated with marked stability for flexion and extension in the parasagittal plane Among these functionally significant traits are the right angle betvleen the medial and lateral astragalotibial facets at the cruroastragalar joint (Fig 1031 m) and the conformation of the transverse tarsal joint characterized by tbe distal and proximal calcaneoshycuboid facet forming a right angle (Fig 1O3n)

(a) (b)

Frugivores Insectivores Frugivores Insectivores

+1 +2

+2 3+3+ 4+ 4+

5 5 +6+6 +7+7 +8+8

9+9 1110 + + 12 + 11 + 12 +

13e13 14e1415 0 15160 1717 160

18 18 20 1919

20 bull 2121

200 250 300 350 150 200 250 300

SRA ratio SRL ratio

Mara Alejandro Abello et a

1043 Feeding habits Plots of SRL and SRA show the separation between extinct and extant frugivorous and insectivorous speCIes (Fig 105) Both ralios indicate that most extinct microshybiotheriids were insectivorous Microbiotherium acicula is the microbiotheriid with the highest SRA and SRL values equaling the living insectivorous Caenolestes caniventer and Sminthopsis crassieaudata 10 SRA ratio The SRL value of Microbiotherium patagonicum is close to that estimated for Dromiciops gliroides while M tehuelchum and M gallegosense present lesser SRL values than D gliroides and M aeicula indicating a less shearing development in these species Microbiotheriurn gallegosense has an SRA value comparable to those of the living Australian frugivores Petaurus breviceps and Acrobates pygmaeus However M galegosense clusters with the modern insectivores based on SRL ratio (Fig 1OSb)

Among pauciluberculatans three species (Abderites meridionalis Aedestis owenn Ameghino 1887 and Palaeothentes aratae Ameghino 1887) cluster with modem frugivores on the basis of SRA and SRL ratios Conversely Phonocdromus gracilis Ameghino 1894 (Fig 102g h) and the palaeothentids Palaeothentes pascuali Bown and Fleashygle 1993 P minutus P intermedius Ameghino 1887 and P lemoinei cluster with the living insectivores Finally the caenolestid Stifotherium dissimife (Fig 1O2e f) and the palaeo then tid Aedestis lemairei are classified as frugivorous or insectivorous depending on shearing ratio (ie as insectshyivore-frugivore Fig 105a b)

Fig 105 Partition be[ween frugivorous and insecLivorous Laxa based on SRA (a) and SRL (b) ratios Paucituberculatans (crosses) petaurids (filled circles) dasyurids (open circles) microbiotherids (diamonds) Specie are I Sfilothlrium dissimile 2 Phonocdromus gracilis 3 Ahderites meridionalis 4 Acdestis owenii 5 Acdestis lemairei 6 Palaeothentes millutlls 7 PalaeOhenle1 pascuafi 8 Palaeolhellres nlermedius 9 Pafaearhenfes lemaine to Palaeorherlres aralae 11 LestQros inca 12 eaenolestes coni Fenter 13 Anechinus stuartii 14 Sminlhopsis crassicaufialO 15 Petaurus breviceps 16 AUobates pygmaells 17 Dromiciops giroides 18 MicroJiorheriulrI acicula 19 Microbiotherillm poagoncum 20 MicrohiorheriunI galiegosellse and 21 Microbiorherium tehLlechum

163 Paleoecology oj Somacrucian Paucifuberculara and Microbiorheria

105 Discussion

1051 Body mass In a study of extant Neotropical marsupials Birney and Monjeau (2003) analyzed the distribution of body size among species and estab lished three size categories (a) small-sized (less than 100 g) (b) medium-sized (from 100 to 499 g) and (c) large-sized (500 g or more) Taking into account these size categories we found that Santacrucian microbiOlheriids were mainly small -sized with estimated body masses ranging from 20 g in MicrobiOlherium acicula to l47 g in M gallegosense (Fig lO2c d) Santac rucian pauc iluberculatans show a much greater body-mass range extending from l3 g in PhoJlocdromus gracilis to 800 g in Paloeothemes aratae and with more than half of the species being small- to medium-sized (Table 101)

Throughout the Cenozoic most South American metashytherians were small- to medium-sized (see Goin 2003) In extant fauuas smaU- to medium-sized marsupials represent about 90 of the marsupial fauna of the Americas (see Birney and Monjeau 2003) and they are also abundant in the marsupial fauna of Australas ia (Dickman and Vieira 2006) Our results are in agreement with this pattern because 52 of the Santaclllcian marsupia species are small- to mediurn-si ~ed (nine paucituberculatans plus four microbiotherLan species see Table 101) and 48 are large (one paucituberculatan species plus II sparassodon( species see Table 101 and Prevosti ef aI Chapter 11 )

Sanracrucian paucitubecculatans and microbiotheriids show a body mass overlap in the small and medium size categories (Fig 106a c) Nevertheless the differential use of space and food resources may have miuimized or avoided competition among spec ies of similar body mass as in extant marsupial ctssemblages (CharleS-Dominique e 01 198 1 Charles-Domiuique 1983 Vte tra and Monteiro-Filho 2003)

10-5_2 Locomotion and use of the substrate Locomotor strategies constitute an imporLant dimension of a species niche For extinct mammals locomotion may be inferred from fossil postcranial remain s and have implicashytions for species paleoecology Unfortunate ly only Iwo skeletons of non-carni vorous Santacrucian marsupi als are known Both skeletons (pertaining to two different palaeothentid spelties) were recently analyzed by Abello and Candela (2010) who paid particular attention to the reconstruction of locomotor pattern As noted earlier in lenns of func tionally significam features Ihe major similarshyities were found with the extant marsupials Caenolesfes juiginosus and Meta(hirus nudicaudofus The latter is the most terrestrial dide lphid (Miles el af 198 1 Delciellos and Vieira 2006 2009) This marsupial inhabits a wide range of forest habitats (Miranda el of 2009) from open scrub

700 600 500 lt0O9

300 9

200 0

t bull bullbull

~ j

__-

_ -

_~ fl

a ~ l

bull ~ a

a

OCO

0 ~----------------------------------I~--

------shy------------- -~------------------------------------4rf__1

~--------------------------------_~f__1

~---------------------------------f~f_~1

~---------------------------p~---~4ri_~1

~--------------------------

~ ~---------------------------~-~---_F~i_~1

I j i ~ Q

6OO0

~

oog

WO

200 ~

1 0 0

b

OO

oo

~

~ ~----------------------------------------1

~-----------------------------------------I

~~-----------------------------------------l

500~------------------------------------__1

OO 9~----------------------------------------_1

300~----------------------------------------_1

~~----------------------~----- --------~

100 Q bullbullbull_ ________ ---- --------shy

c

Fig 106 Body mass averages of insecrivorous (a) frugivorous (b) and insec tiv orou~-rrug ivorous (c) non -camivorollS marsupi als of Santa CruL Formalion Gray bars paueitubercul utans black bars microbiotherjids Values fro m Table 101

164

vegetation (M il es ef at (981) to lowland and hill side woodlands (Moraes 2004) In the wild it was observed bonnding on the ground swiftly negotia ting obstacles at high speed (Miles el 01 198 J) Caenofesles species occur in the Andean highlands biomes such as Montane and e land forestlt and Paramo In these biomes caenoles tids inhabit forests with or without dense undergrowth and the grassland- forest ecotone (Ki rsh and Waller 1979 Albuja and Patterson 1996) Coenoestes and its relative Lestoros cau leap at high speed using anterior and posterior limbs simultaneously (Kirsh and Waller 1979)

Locomotor behaviors of M nudicaudatus and caenolesshylids have clear anatomical correlates in the ir poslcraniai skeletons (Grand 1983 Argot 2003a b) a particularly importan l aspect for functi ona l intetpretations in fossil species Pa faeoth entes species exhi bit en hanced joint stashybility and parasagittal movement (Abello and Cande la 2010) Addi tiona lly features associated with fa st moveshyments and leaping have been identified In conclusion P minutus and P lemoinei were probably agile species with running and leaping abilities resembling Caenolestes Lesforos and Merachirus

Even though the locomotor strategies described by AbeHu and Candela (20 I0) were established for only two Palaeorhenles species il may be speculaled that other species of the genus such as P pascuai and P i11lermedius may have had similar locomofor abilities In ilddition it is possible that scansorial or arboreal locomotor behaviors evolved among non-camivorous Santacruciall marsupiaLs

We note that the ecological diversity o[ nOll-carui vorons Santacrucian marsupials evaluated here is simil ar to thal of CU1Tent tropical habitats of South America (see below) In extant ecosyslems) ecological diversity is positively corre lshyated with habitat complexi ty (ie with the development of vert ical strata in a habitat August 1983) In the case of Santacrucian marsupials the ecological diversity inferred here would seem to reflect a vertical heterogeneity In this comext it is possible to infer that [he vertical space of these habi tats could be exploi ted by Santacrucian marsupials through scansoria l andor arboreal habi ts Vertical space offers an additional dimens ion for niche partitioning and hence the possibility of more species coexisting in the same area (Mi les et al 198 I Vieira and Monteiro-Filho 2003 Croft and Eisenberg 2006 and references there in)

1053 Feeding habits According to the cro wn morphology of its molars Miocene microbiotheri ids were considered insectivores or insec(shyivoresfrugivores (Pascual and Bond 1986 Goin 1997) Based on an analysis of molar wear facels Goin e al (jn press) concluded that Early Oligocene Patagonian members of this family (including Microhiotherium ltJ genus that we analyzed in this study) were insecti vores

Maria Alejandro Abello et al

According (Q our results Miocene microbiotheJiids also were mainly insec ti vores Only one s~cies M gaJlegosense has shearing wtios that indicate a more limited shearing component suggesting an insectivorous-frugivorous diet (Fig 105a b) Microbiotherium acicula is tile most exLreme insectivorous species showing the highest SRL and SRA va lues Microbiotherium palaROnicum is closer to the extant Dromiciops giiroides in SRL va lues aud it achieved a similar degree of molar crest developme ut as in the living species

In our analysis D gliroides is grouped wi th insecti vorous species (Fig 105a b) This resu lt is consistent with the information of its main dietary prefe rences in the wild Analys is of stomach contenrs indicated that this species feeds primarily on arlhropods and othe r inveltebrates (Mann 1955 Meserve et 01 1988) Howeve r it also feeds seasonall y on fruits (Amico ef af 2009) This strategy could be extrapolated to SanLacJlJcian microbiotherijds as insectivores may consume plant material either regularl y or seasonally when prey species are scarce or unavailable (Hume 2003)

According to molar crown morphOlogy Miocene paucituberculatans were considered insec ti vores insectshyivores-frug ivores and insec tivores- phytophages (eg Ortiz-Jaureguizar 2003) Our ana lys is corroborates this inference showing that insec(j vores are more di verse (five species) than insectivore- frugivores and frugivores (induding the insec tivorous-phytophagous category of Ortiz-Jaureguir 2003 see above) (Table 101) As Dumont et af (2000) pointed out folivory seems not to

have evolved in pauci rn berculatans as no taxon with high shear ing ratios has an es timated body mass higher than 600 g (Smith and Lee 1984)

Most insecti vorous paucittlberculatans di ffer markedly in body magtS (eg Palaeothentes milluus P intermedius and P lenlOnei) suggesting that ecological separation among them may have been achi eved by differences in dietary composi tion andor consumption of prey of different body size In living insectivores such as dasyurid marsushypials and soricid piacentaLs there is a positive cOlTe lalion between body size of predators and their prey (Fisher and Dickman 1993 ChLlrchfield e aI 1999) Even so both small and large dasyurids can exploit a relatively large range of prey sizes and there is no phys ical constraint on the size of prey consumed Consequently dasyurid species max imized their rates of energy intake by feeding on prey of a selec ted size (Fisher and Dickman 1993) Thus larger dasyurids prefer larger invertebrates because of grea ter energy return per prey item conversely for he smaller dasyurids prey consumption requi res more chewing time and this could resull in a fall in the rale of energy intake from eacb prey (Fisher nd Dickman 1993) Despite small differences in body size and overall ecology niche overlap is minimized in shrews as they differ in terms of the

162

such as CQenolestesfuliginosus and Metachirus nudicaudalus (Abello and Candela 2010) Characteristics of the forelimbs include among other features a deep and high humeral trochlea (Fig 103a) a deep olecranon fossa (Fig JO3b) and mediolaterally broad proximal trochlear crest (Fig lO3c d) These featmes indicate a well-stabilized elbow joint The short lateral epicondylar crest (Fig 103b) and the suboval radial head (Fig lO3e) suggest that pronation-supinshyation was limited (Abello and Candela 2010 1520) The pelvis better preserved in P minutus shows a restrictive acetabulum (ie tightly articulating Szalay and Sargis 2001) lengthened ischium and prominent femoral tubercle as well as ischial ruberosity (Fig 1O3g) The morphology of the pelvis indicates a high stability at the ilio-femoral joint and an increased mechanical advantage of the flexors and extensors of the hip (ie rectus femoris and hamstring muscles) which are well developed in saltatorial species (Argot 2003a) The greater trochanter of the femur projects beyond the proximal surface of the femoral head (Fig 103i) indicating that the gluteal muscles were favorably positioned to produce fast extension at the hip joint as occms in agile and leaping species Additionally the hind limbs of Palaeothentes species like those of curso-saltatorial f0I111s have features associated with marked stability for flexion and extension in the parasagittal plane Among these functionally significant traits are the right angle betvleen the medial and lateral astragalotibial facets at the cruroastragalar joint (Fig 1031 m) and the conformation of the transverse tarsal joint characterized by tbe distal and proximal calcaneoshycuboid facet forming a right angle (Fig 1O3n)

(a) (b)

Frugivores Insectivores Frugivores Insectivores

+1 +2

+2 3+3+ 4+ 4+

5 5 +6+6 +7+7 +8+8

9+9 1110 + + 12 + 11 + 12 +

13e13 14e1415 0 15160 1717 160

18 18 20 1919

20 bull 2121

200 250 300 350 150 200 250 300

SRA ratio SRL ratio

Mara Alejandro Abello et a

1043 Feeding habits Plots of SRL and SRA show the separation between extinct and extant frugivorous and insectivorous speCIes (Fig 105) Both ralios indicate that most extinct microshybiotheriids were insectivorous Microbiotherium acicula is the microbiotheriid with the highest SRA and SRL values equaling the living insectivorous Caenolestes caniventer and Sminthopsis crassieaudata 10 SRA ratio The SRL value of Microbiotherium patagonicum is close to that estimated for Dromiciops gliroides while M tehuelchum and M gallegosense present lesser SRL values than D gliroides and M aeicula indicating a less shearing development in these species Microbiotheriurn gallegosense has an SRA value comparable to those of the living Australian frugivores Petaurus breviceps and Acrobates pygmaeus However M galegosense clusters with the modern insectivores based on SRL ratio (Fig 1OSb)

Among pauciluberculatans three species (Abderites meridionalis Aedestis owenn Ameghino 1887 and Palaeothentes aratae Ameghino 1887) cluster with modem frugivores on the basis of SRA and SRL ratios Conversely Phonocdromus gracilis Ameghino 1894 (Fig 102g h) and the palaeothentids Palaeothentes pascuali Bown and Fleashygle 1993 P minutus P intermedius Ameghino 1887 and P lemoinei cluster with the living insectivores Finally the caenolestid Stifotherium dissimife (Fig 1O2e f) and the palaeo then tid Aedestis lemairei are classified as frugivorous or insectivorous depending on shearing ratio (ie as insectshyivore-frugivore Fig 105a b)

Fig 105 Partition be[ween frugivorous and insecLivorous Laxa based on SRA (a) and SRL (b) ratios Paucituberculatans (crosses) petaurids (filled circles) dasyurids (open circles) microbiotherids (diamonds) Specie are I Sfilothlrium dissimile 2 Phonocdromus gracilis 3 Ahderites meridionalis 4 Acdestis owenii 5 Acdestis lemairei 6 Palaeothentes millutlls 7 PalaeOhenle1 pascuafi 8 Palaeolhellres nlermedius 9 Pafaearhenfes lemaine to Palaeorherlres aralae 11 LestQros inca 12 eaenolestes coni Fenter 13 Anechinus stuartii 14 Sminlhopsis crassicaufialO 15 Petaurus breviceps 16 AUobates pygmaells 17 Dromiciops giroides 18 MicroJiorheriulrI acicula 19 Microbiotherillm poagoncum 20 MicrohiorheriunI galiegosellse and 21 Microbiorherium tehLlechum

163 Paleoecology oj Somacrucian Paucifuberculara and Microbiorheria

105 Discussion

1051 Body mass In a study of extant Neotropical marsupials Birney and Monjeau (2003) analyzed the distribution of body size among species and estab lished three size categories (a) small-sized (less than 100 g) (b) medium-sized (from 100 to 499 g) and (c) large-sized (500 g or more) Taking into account these size categories we found that Santacrucian microbiOlheriids were mainly small -sized with estimated body masses ranging from 20 g in MicrobiOlherium acicula to l47 g in M gallegosense (Fig lO2c d) Santac rucian pauc iluberculatans show a much greater body-mass range extending from l3 g in PhoJlocdromus gracilis to 800 g in Paloeothemes aratae and with more than half of the species being small- to medium-sized (Table 101)

Throughout the Cenozoic most South American metashytherians were small- to medium-sized (see Goin 2003) In extant fauuas smaU- to medium-sized marsupials represent about 90 of the marsupial fauna of the Americas (see Birney and Monjeau 2003) and they are also abundant in the marsupial fauna of Australas ia (Dickman and Vieira 2006) Our results are in agreement with this pattern because 52 of the Santaclllcian marsupia species are small- to mediurn-si ~ed (nine paucituberculatans plus four microbiotherLan species see Table 101) and 48 are large (one paucituberculatan species plus II sparassodon( species see Table 101 and Prevosti ef aI Chapter 11 )

Sanracrucian paucitubecculatans and microbiotheriids show a body mass overlap in the small and medium size categories (Fig 106a c) Nevertheless the differential use of space and food resources may have miuimized or avoided competition among spec ies of similar body mass as in extant marsupial ctssemblages (CharleS-Dominique e 01 198 1 Charles-Domiuique 1983 Vte tra and Monteiro-Filho 2003)

10-5_2 Locomotion and use of the substrate Locomotor strategies constitute an imporLant dimension of a species niche For extinct mammals locomotion may be inferred from fossil postcranial remain s and have implicashytions for species paleoecology Unfortunate ly only Iwo skeletons of non-carni vorous Santacrucian marsupi als are known Both skeletons (pertaining to two different palaeothentid spelties) were recently analyzed by Abello and Candela (2010) who paid particular attention to the reconstruction of locomotor pattern As noted earlier in lenns of func tionally significam features Ihe major similarshyities were found with the extant marsupials Caenolesfes juiginosus and Meta(hirus nudicaudofus The latter is the most terrestrial dide lphid (Miles el af 198 1 Delciellos and Vieira 2006 2009) This marsupial inhabits a wide range of forest habitats (Miranda el of 2009) from open scrub

700 600 500 lt0O9

300 9

200 0

t bull bullbull

~ j

__-

_ -

_~ fl

a ~ l

bull ~ a

a

OCO

0 ~----------------------------------I~--

------shy------------- -~------------------------------------4rf__1

~--------------------------------_~f__1

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~--------------------------

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I j i ~ Q

6OO0

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1 0 0

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~ ~----------------------------------------1

~-----------------------------------------I

~~-----------------------------------------l

500~------------------------------------__1

OO 9~----------------------------------------_1

300~----------------------------------------_1

~~----------------------~----- --------~

100 Q bullbullbull_ ________ ---- --------shy

c

Fig 106 Body mass averages of insecrivorous (a) frugivorous (b) and insec tiv orou~-rrug ivorous (c) non -camivorollS marsupi als of Santa CruL Formalion Gray bars paueitubercul utans black bars microbiotherjids Values fro m Table 101

164

vegetation (M il es ef at (981) to lowland and hill side woodlands (Moraes 2004) In the wild it was observed bonnding on the ground swiftly negotia ting obstacles at high speed (Miles el 01 198 J) Caenofesles species occur in the Andean highlands biomes such as Montane and e land forestlt and Paramo In these biomes caenoles tids inhabit forests with or without dense undergrowth and the grassland- forest ecotone (Ki rsh and Waller 1979 Albuja and Patterson 1996) Coenoestes and its relative Lestoros cau leap at high speed using anterior and posterior limbs simultaneously (Kirsh and Waller 1979)

Locomotor behaviors of M nudicaudatus and caenolesshylids have clear anatomical correlates in the ir poslcraniai skeletons (Grand 1983 Argot 2003a b) a particularly importan l aspect for functi ona l intetpretations in fossil species Pa faeoth entes species exhi bit en hanced joint stashybility and parasagittal movement (Abello and Cande la 2010) Addi tiona lly features associated with fa st moveshyments and leaping have been identified In conclusion P minutus and P lemoinei were probably agile species with running and leaping abilities resembling Caenolestes Lesforos and Merachirus

Even though the locomotor strategies described by AbeHu and Candela (20 I0) were established for only two Palaeorhenles species il may be speculaled that other species of the genus such as P pascuai and P i11lermedius may have had similar locomofor abilities In ilddition it is possible that scansorial or arboreal locomotor behaviors evolved among non-camivorous Santacruciall marsupiaLs

We note that the ecological diversity o[ nOll-carui vorons Santacrucian marsupials evaluated here is simil ar to thal of CU1Tent tropical habitats of South America (see below) In extant ecosyslems) ecological diversity is positively corre lshyated with habitat complexi ty (ie with the development of vert ical strata in a habitat August 1983) In the case of Santacrucian marsupials the ecological diversity inferred here would seem to reflect a vertical heterogeneity In this comext it is possible to infer that [he vertical space of these habi tats could be exploi ted by Santacrucian marsupials through scansoria l andor arboreal habi ts Vertical space offers an additional dimens ion for niche partitioning and hence the possibility of more species coexisting in the same area (Mi les et al 198 I Vieira and Monteiro-Filho 2003 Croft and Eisenberg 2006 and references there in)

1053 Feeding habits According to the cro wn morphology of its molars Miocene microbiotheri ids were considered insectivores or insec(shyivoresfrugivores (Pascual and Bond 1986 Goin 1997) Based on an analysis of molar wear facels Goin e al (jn press) concluded that Early Oligocene Patagonian members of this family (including Microhiotherium ltJ genus that we analyzed in this study) were insecti vores

Maria Alejandro Abello et al

According (Q our results Miocene microbiotheJiids also were mainly insec ti vores Only one s~cies M gaJlegosense has shearing wtios that indicate a more limited shearing component suggesting an insectivorous-frugivorous diet (Fig 105a b) Microbiotherium acicula is tile most exLreme insectivorous species showing the highest SRL and SRA va lues Microbiotherium palaROnicum is closer to the extant Dromiciops giiroides in SRL va lues aud it achieved a similar degree of molar crest developme ut as in the living species

In our analysis D gliroides is grouped wi th insecti vorous species (Fig 105a b) This resu lt is consistent with the information of its main dietary prefe rences in the wild Analys is of stomach contenrs indicated that this species feeds primarily on arlhropods and othe r inveltebrates (Mann 1955 Meserve et 01 1988) Howeve r it also feeds seasonall y on fruits (Amico ef af 2009) This strategy could be extrapolated to SanLacJlJcian microbiotherijds as insectivores may consume plant material either regularl y or seasonally when prey species are scarce or unavailable (Hume 2003)

According to molar crown morphOlogy Miocene paucituberculatans were considered insec ti vores insectshyivores-frug ivores and insec tivores- phytophages (eg Ortiz-Jaureguizar 2003) Our ana lys is corroborates this inference showing that insec(j vores are more di verse (five species) than insectivore- frugivores and frugivores (induding the insec tivorous-phytophagous category of Ortiz-Jaureguir 2003 see above) (Table 101) As Dumont et af (2000) pointed out folivory seems not to

have evolved in pauci rn berculatans as no taxon with high shear ing ratios has an es timated body mass higher than 600 g (Smith and Lee 1984)

Most insecti vorous paucittlberculatans di ffer markedly in body magtS (eg Palaeothentes milluus P intermedius and P lenlOnei) suggesting that ecological separation among them may have been achi eved by differences in dietary composi tion andor consumption of prey of different body size In living insectivores such as dasyurid marsushypials and soricid piacentaLs there is a positive cOlTe lalion between body size of predators and their prey (Fisher and Dickman 1993 ChLlrchfield e aI 1999) Even so both small and large dasyurids can exploit a relatively large range of prey sizes and there is no phys ical constraint on the size of prey consumed Consequently dasyurid species max imized their rates of energy intake by feeding on prey of a selec ted size (Fisher and Dickman 1993) Thus larger dasyurids prefer larger invertebrates because of grea ter energy return per prey item conversely for he smaller dasyurids prey consumption requi res more chewing time and this could resull in a fall in the rale of energy intake from eacb prey (Fisher nd Dickman 1993) Despite small differences in body size and overall ecology niche overlap is minimized in shrews as they differ in terms of the

163 Paleoecology oj Somacrucian Paucifuberculara and Microbiorheria

105 Discussion

1051 Body mass In a study of extant Neotropical marsupials Birney and Monjeau (2003) analyzed the distribution of body size among species and estab lished three size categories (a) small-sized (less than 100 g) (b) medium-sized (from 100 to 499 g) and (c) large-sized (500 g or more) Taking into account these size categories we found that Santacrucian microbiOlheriids were mainly small -sized with estimated body masses ranging from 20 g in MicrobiOlherium acicula to l47 g in M gallegosense (Fig lO2c d) Santac rucian pauc iluberculatans show a much greater body-mass range extending from l3 g in PhoJlocdromus gracilis to 800 g in Paloeothemes aratae and with more than half of the species being small- to medium-sized (Table 101)

Throughout the Cenozoic most South American metashytherians were small- to medium-sized (see Goin 2003) In extant fauuas smaU- to medium-sized marsupials represent about 90 of the marsupial fauna of the Americas (see Birney and Monjeau 2003) and they are also abundant in the marsupial fauna of Australas ia (Dickman and Vieira 2006) Our results are in agreement with this pattern because 52 of the Santaclllcian marsupia species are small- to mediurn-si ~ed (nine paucituberculatans plus four microbiotherLan species see Table 101) and 48 are large (one paucituberculatan species plus II sparassodon( species see Table 101 and Prevosti ef aI Chapter 11 )

Sanracrucian paucitubecculatans and microbiotheriids show a body mass overlap in the small and medium size categories (Fig 106a c) Nevertheless the differential use of space and food resources may have miuimized or avoided competition among spec ies of similar body mass as in extant marsupial ctssemblages (CharleS-Dominique e 01 198 1 Charles-Domiuique 1983 Vte tra and Monteiro-Filho 2003)

10-5_2 Locomotion and use of the substrate Locomotor strategies constitute an imporLant dimension of a species niche For extinct mammals locomotion may be inferred from fossil postcranial remain s and have implicashytions for species paleoecology Unfortunate ly only Iwo skeletons of non-carni vorous Santacrucian marsupi als are known Both skeletons (pertaining to two different palaeothentid spelties) were recently analyzed by Abello and Candela (2010) who paid particular attention to the reconstruction of locomotor pattern As noted earlier in lenns of func tionally significam features Ihe major similarshyities were found with the extant marsupials Caenolesfes juiginosus and Meta(hirus nudicaudofus The latter is the most terrestrial dide lphid (Miles el af 198 1 Delciellos and Vieira 2006 2009) This marsupial inhabits a wide range of forest habitats (Miranda el of 2009) from open scrub

700 600 500 lt0O9

300 9

200 0

t bull bullbull

~ j

__-

_ -

_~ fl

a ~ l

bull ~ a

a

OCO

0 ~----------------------------------I~--

------shy------------- -~------------------------------------4rf__1

~--------------------------------_~f__1

~---------------------------------f~f_~1

~---------------------------p~---~4ri_~1

~--------------------------

~ ~---------------------------~-~---_F~i_~1

I j i ~ Q

6OO0

~

oog

WO

200 ~

1 0 0

b

OO

oo

~

~ ~----------------------------------------1

~-----------------------------------------I

~~-----------------------------------------l

500~------------------------------------__1

OO 9~----------------------------------------_1

300~----------------------------------------_1

~~----------------------~----- --------~

100 Q bullbullbull_ ________ ---- --------shy

c

Fig 106 Body mass averages of insecrivorous (a) frugivorous (b) and insec tiv orou~-rrug ivorous (c) non -camivorollS marsupi als of Santa CruL Formalion Gray bars paueitubercul utans black bars microbiotherjids Values fro m Table 101

164

vegetation (M il es ef at (981) to lowland and hill side woodlands (Moraes 2004) In the wild it was observed bonnding on the ground swiftly negotia ting obstacles at high speed (Miles el 01 198 J) Caenofesles species occur in the Andean highlands biomes such as Montane and e land forestlt and Paramo In these biomes caenoles tids inhabit forests with or without dense undergrowth and the grassland- forest ecotone (Ki rsh and Waller 1979 Albuja and Patterson 1996) Coenoestes and its relative Lestoros cau leap at high speed using anterior and posterior limbs simultaneously (Kirsh and Waller 1979)

Locomotor behaviors of M nudicaudatus and caenolesshylids have clear anatomical correlates in the ir poslcraniai skeletons (Grand 1983 Argot 2003a b) a particularly importan l aspect for functi ona l intetpretations in fossil species Pa faeoth entes species exhi bit en hanced joint stashybility and parasagittal movement (Abello and Cande la 2010) Addi tiona lly features associated with fa st moveshyments and leaping have been identified In conclusion P minutus and P lemoinei were probably agile species with running and leaping abilities resembling Caenolestes Lesforos and Merachirus

Even though the locomotor strategies described by AbeHu and Candela (20 I0) were established for only two Palaeorhenles species il may be speculaled that other species of the genus such as P pascuai and P i11lermedius may have had similar locomofor abilities In ilddition it is possible that scansorial or arboreal locomotor behaviors evolved among non-camivorous Santacruciall marsupiaLs

We note that the ecological diversity o[ nOll-carui vorons Santacrucian marsupials evaluated here is simil ar to thal of CU1Tent tropical habitats of South America (see below) In extant ecosyslems) ecological diversity is positively corre lshyated with habitat complexi ty (ie with the development of vert ical strata in a habitat August 1983) In the case of Santacrucian marsupials the ecological diversity inferred here would seem to reflect a vertical heterogeneity In this comext it is possible to infer that [he vertical space of these habi tats could be exploi ted by Santacrucian marsupials through scansoria l andor arboreal habi ts Vertical space offers an additional dimens ion for niche partitioning and hence the possibility of more species coexisting in the same area (Mi les et al 198 I Vieira and Monteiro-Filho 2003 Croft and Eisenberg 2006 and references there in)

1053 Feeding habits According to the cro wn morphology of its molars Miocene microbiotheri ids were considered insectivores or insec(shyivoresfrugivores (Pascual and Bond 1986 Goin 1997) Based on an analysis of molar wear facels Goin e al (jn press) concluded that Early Oligocene Patagonian members of this family (including Microhiotherium ltJ genus that we analyzed in this study) were insecti vores

Maria Alejandro Abello et al

According (Q our results Miocene microbiotheJiids also were mainly insec ti vores Only one s~cies M gaJlegosense has shearing wtios that indicate a more limited shearing component suggesting an insectivorous-frugivorous diet (Fig 105a b) Microbiotherium acicula is tile most exLreme insectivorous species showing the highest SRL and SRA va lues Microbiotherium palaROnicum is closer to the extant Dromiciops giiroides in SRL va lues aud it achieved a similar degree of molar crest developme ut as in the living species

In our analysis D gliroides is grouped wi th insecti vorous species (Fig 105a b) This resu lt is consistent with the information of its main dietary prefe rences in the wild Analys is of stomach contenrs indicated that this species feeds primarily on arlhropods and othe r inveltebrates (Mann 1955 Meserve et 01 1988) Howeve r it also feeds seasonall y on fruits (Amico ef af 2009) This strategy could be extrapolated to SanLacJlJcian microbiotherijds as insectivores may consume plant material either regularl y or seasonally when prey species are scarce or unavailable (Hume 2003)

According to molar crown morphOlogy Miocene paucituberculatans were considered insec ti vores insectshyivores-frug ivores and insec tivores- phytophages (eg Ortiz-Jaureguizar 2003) Our ana lys is corroborates this inference showing that insec(j vores are more di verse (five species) than insectivore- frugivores and frugivores (induding the insec tivorous-phytophagous category of Ortiz-Jaureguir 2003 see above) (Table 101) As Dumont et af (2000) pointed out folivory seems not to

have evolved in pauci rn berculatans as no taxon with high shear ing ratios has an es timated body mass higher than 600 g (Smith and Lee 1984)

Most insecti vorous paucittlberculatans di ffer markedly in body magtS (eg Palaeothentes milluus P intermedius and P lenlOnei) suggesting that ecological separation among them may have been achi eved by differences in dietary composi tion andor consumption of prey of different body size In living insectivores such as dasyurid marsushypials and soricid piacentaLs there is a positive cOlTe lalion between body size of predators and their prey (Fisher and Dickman 1993 ChLlrchfield e aI 1999) Even so both small and large dasyurids can exploit a relatively large range of prey sizes and there is no phys ical constraint on the size of prey consumed Consequently dasyurid species max imized their rates of energy intake by feeding on prey of a selec ted size (Fisher and Dickman 1993) Thus larger dasyurids prefer larger invertebrates because of grea ter energy return per prey item conversely for he smaller dasyurids prey consumption requi res more chewing time and this could resull in a fall in the rale of energy intake from eacb prey (Fisher nd Dickman 1993) Despite small differences in body size and overall ecology niche overlap is minimized in shrews as they differ in terms of the

164

vegetation (M il es ef at (981) to lowland and hill side woodlands (Moraes 2004) In the wild it was observed bonnding on the ground swiftly negotia ting obstacles at high speed (Miles el 01 198 J) Caenofesles species occur in the Andean highlands biomes such as Montane and e land forestlt and Paramo In these biomes caenoles tids inhabit forests with or without dense undergrowth and the grassland- forest ecotone (Ki rsh and Waller 1979 Albuja and Patterson 1996) Coenoestes and its relative Lestoros cau leap at high speed using anterior and posterior limbs simultaneously (Kirsh and Waller 1979)

Locomotor behaviors of M nudicaudatus and caenolesshylids have clear anatomical correlates in the ir poslcraniai skeletons (Grand 1983 Argot 2003a b) a particularly importan l aspect for functi ona l intetpretations in fossil species Pa faeoth entes species exhi bit en hanced joint stashybility and parasagittal movement (Abello and Cande la 2010) Addi tiona lly features associated with fa st moveshyments and leaping have been identified In conclusion P minutus and P lemoinei were probably agile species with running and leaping abilities resembling Caenolestes Lesforos and Merachirus

Even though the locomotor strategies described by AbeHu and Candela (20 I0) were established for only two Palaeorhenles species il may be speculaled that other species of the genus such as P pascuai and P i11lermedius may have had similar locomofor abilities In ilddition it is possible that scansorial or arboreal locomotor behaviors evolved among non-camivorous Santacruciall marsupiaLs

We note that the ecological diversity o[ nOll-carui vorons Santacrucian marsupials evaluated here is simil ar to thal of CU1Tent tropical habitats of South America (see below) In extant ecosyslems) ecological diversity is positively corre lshyated with habitat complexi ty (ie with the development of vert ical strata in a habitat August 1983) In the case of Santacrucian marsupials the ecological diversity inferred here would seem to reflect a vertical heterogeneity In this comext it is possible to infer that [he vertical space of these habi tats could be exploi ted by Santacrucian marsupials through scansoria l andor arboreal habi ts Vertical space offers an additional dimens ion for niche partitioning and hence the possibility of more species coexisting in the same area (Mi les et al 198 I Vieira and Monteiro-Filho 2003 Croft and Eisenberg 2006 and references there in)

1053 Feeding habits According to the cro wn morphology of its molars Miocene microbiotheri ids were considered insectivores or insec(shyivoresfrugivores (Pascual and Bond 1986 Goin 1997) Based on an analysis of molar wear facels Goin e al (jn press) concluded that Early Oligocene Patagonian members of this family (including Microhiotherium ltJ genus that we analyzed in this study) were insecti vores

Maria Alejandro Abello et al

According (Q our results Miocene microbiotheJiids also were mainly insec ti vores Only one s~cies M gaJlegosense has shearing wtios that indicate a more limited shearing component suggesting an insectivorous-frugivorous diet (Fig 105a b) Microbiotherium acicula is tile most exLreme insectivorous species showing the highest SRL and SRA va lues Microbiotherium palaROnicum is closer to the extant Dromiciops giiroides in SRL va lues aud it achieved a similar degree of molar crest developme ut as in the living species

In our analysis D gliroides is grouped wi th insecti vorous species (Fig 105a b) This resu lt is consistent with the information of its main dietary prefe rences in the wild Analys is of stomach contenrs indicated that this species feeds primarily on arlhropods and othe r inveltebrates (Mann 1955 Meserve et 01 1988) Howeve r it also feeds seasonall y on fruits (Amico ef af 2009) This strategy could be extrapolated to SanLacJlJcian microbiotherijds as insectivores may consume plant material either regularl y or seasonally when prey species are scarce or unavailable (Hume 2003)

According to molar crown morphOlogy Miocene paucituberculatans were considered insec ti vores insectshyivores-frug ivores and insec tivores- phytophages (eg Ortiz-Jaureguizar 2003) Our ana lys is corroborates this inference showing that insec(j vores are more di verse (five species) than insectivore- frugivores and frugivores (induding the insec tivorous-phytophagous category of Ortiz-Jaureguir 2003 see above) (Table 101) As Dumont et af (2000) pointed out folivory seems not to

have evolved in pauci rn berculatans as no taxon with high shear ing ratios has an es timated body mass higher than 600 g (Smith and Lee 1984)

Most insecti vorous paucittlberculatans di ffer markedly in body magtS (eg Palaeothentes milluus P intermedius and P lenlOnei) suggesting that ecological separation among them may have been achi eved by differences in dietary composi tion andor consumption of prey of different body size In living insectivores such as dasyurid marsushypials and soricid piacentaLs there is a positive cOlTe lalion between body size of predators and their prey (Fisher and Dickman 1993 ChLlrchfield e aI 1999) Even so both small and large dasyurids can exploit a relatively large range of prey sizes and there is no phys ical constraint on the size of prey consumed Consequently dasyurid species max imized their rates of energy intake by feeding on prey of a selec ted size (Fisher and Dickman 1993) Thus larger dasyurids prefer larger invertebrates because of grea ter energy return per prey item conversely for he smaller dasyurids prey consumption requi res more chewing time and this could resull in a fall in the rale of energy intake from eacb prey (Fisher nd Dickman 1993) Despite small differences in body size and overall ecology niche overlap is minimized in shrews as they differ in terms of the

165 Paleoecoogy of Santacrucian Poucifubercuata and Microbiotheria

Fig 107 Life reconstructions a Abderitcs meridlonalis and b Palacothcl7f(S minulls Drawing by Pablo Motta

percentage of several invertebrate prey in the diet (Churchshyfie ld ef 01 1999) We expect that dietary composition (as it covaries with body size) would have produced niche separshyation among extinct insectivorous paucituberculatans

As mentioned above the body mass of Santacrucian microbiotheriids and paucituberculatans overlaps to some degree in the small to medium size range (Fig 106a) initia lly suggesting that some niche overlap may have occurred However differences in body size and molar morphology suggest that niche ove rlap was in fact minshyimal and it is also possible that differences occurred not only in diet composition but also in foraging mode (Sanshyson 1985 Churchfie ld and Shefre l 1994 Church field el al 1999)

Fmgivorous and insectivorous- frugivorous marsupials analyzed here do Ilot exhibit body mass overlap (compare Fig 1O6b widl IO6c) Frugivorous species are paucitu bershyculatans belonging to Palaeothen(idae (PalaeOfhenles oraae

and Acdestis owenii Fig 1O2k l) and Abderitidae (Abderites meridiOllolis Figs IO2m n and 107a) which are quile diSlinc l in dental morphology (Abello 2(07) The dent il ion of Abderitidae is characleJ zed by the presence of well shydeveloped lophs and a plagiaulacoid complex (S impson 1933 Ortiz-Jaureguiz3r 2003) The plag iaulacoid complex of Abderiles was considered by Dumont el al (2000) a a dieta lY indicator in addi tion to body mass and extent of molar shearing According to their analysis occlusion between P3 and ml in Abderitemiddot was a shearing complex that operated in a manner sim ilar to that of hving Australian phalangerids such as Phalanger but dissimilar to those of other mammals with pJagiauJacoid dentition such as certain Cretaceous 10

Early Eocene multituberculates (eg the cimolodontan Plilodus Cope 1881) and North American Paleocene

pJesiadapifoffil primates (eg CaJpodaptes Matthew and Granger 1921) In the 1l1ultituberculates and plesiadapishyforms the shearing teeth mainly exhibit apical wear because the lower cutting teetb become wom when the food is ground against a cllspate upper tooth In contrast in Phalanger and probably also in Abderites the food items are Cll t between the upper and lower teeth as they shear across one anotber in a scissor-like fashion (Dumont et al 2(00) A shearing comshyplex similar to that of the abderitids occurs in many extant Diprotodonta including thc Phalanger already mentioned as well as Burramys and the Potoroidae HypsiprymnodolJ and Bettongia Related to their function these denial modificashytions arc adequate to bJ(ak open food items with a hard covering (Dimpel and Calaby 1972 Parker 1973)

On the othcr hand Palaeolhentes araae and Acdestis owenii have a strong shearing crest (paracri sta) ou m I (Fig 102k I) but they lack a plagiaulacoid dentition and lophs These differences suggest that frugivorous paucitushyherculatans were distinct not only in body mass but in the ir diets as well (Ortiz-Jaureguizar 2003)

1054 Paleoenvironmental implications From thc wide range of estimated body masses and diet of non-carni vorous Santacruc ian marsupials severa l ecologic niches were reconstructed smaJl- (0 medium -sized insectshyivores and small to large frugi vores and insecti voresshyfru givores In regard Lo a paleoecological reconstruction this ecological diversity suggests the existence of foresled habitats that couid have sUpp0l1ed the diverse marsupial niches in modem ecosystems and particularly in tropical forests high values of mammalian species richness arise from habitat heterogencity mainly owing to the pa11itioned vertical space (Augusl 1983 Bakker and Kell 2000)

166

Species richness also tracks plant prodncri vity with higher productivity leading 0 more species (Kay el aI 1997)

Paleoenvi ronmental inferences can also be advanced by analyzing the trophic g uild slrUCl11re of Santacrucian marshysupials In a macroecologicai study of Neotropical marsushypials Birney and Monjeau (2003) evaluated the latitudinal

variation among several biological characters such as trophic guild structure habitat use and body size Taking into account that latitude is a surrogate fo r physical environshy

mental variables sucb as tempera ture and precipitation the trophic guild structure of Santacrucian marsllpials may offer clues to the Santacrucian paleoenvironments According to Birney and Monjeau (2003) three guilds were considered frugivores carnivores and insecti vores Current carnivorshyous marsupials include among othe rs the didelphids Didelphis LUfJeolino and Philander all o f them having

body masses less lhan 2 kg In the Sltt ntacruc ian assemblage ca ll1i vores with body masses less than or equal to 2 kg include the sparassodonts Sipaocyon gracilis Ameghino S obusfa Ameghino Pselldol1OiClis plisi llus Ameghino and Perarhereures pU118ens Ameghino (see Prevosti e al

Chapter I I) Thus smaJt carni vores represent 22 of the

Sanracrucian marsupia l species richness insectivore-frugishyvores plus frugivores 33 and insectivores 45 Comparshying the trophic g uild structure of Santacrucian marsupials with those of the modern Neol-ropics we find that in the Santacrucian fauna there is ltI relatively high percentage of frugivores in relation to camivores a ratio that occurs at low latitudes in the ex tant marsupial faunas of South Amershy

ica Birney and Monjeau (2003) concluded that the thelmal range (ie the difference between mean maximum extreme temperatures and mean minimum extreme temperatures) is the best predictor of the proporti on of frug ivores and camishyvores Closer to the equator the narrower thermal range allows year- long ava ilab ility of fmits and the percentage of

frug ivores is hig her lhan at high latitudes Additionall y differences in precipita tio n (ie seasonaJ ra infa ll) seem [ 0

be anothe r impo rta nt factor influe nc ing the abundance of frug ivores (Bimey and Monjeau 2003) If we cons ider this last factor the sharp differences between dry and wet season ~ in the tropics would have allowed more diversifishycalion in the trophic niche than more constan t precipitation

On the basis on these eco logical similarities we can infer that Santacl1lcian marsupia ls lived in relatively wann clishymates bUl with seasonal rainfall However it should he kept in mind that taphonomic bias and time averaging are common fac tors that affect the composition of fossil assemshy

blages Consequently in the absence of a precise evaluation of the incidence of these biases the infereuces derived from

a fossil assemblage have a less heuristic value that those based on living assemblages

In summary the ecological characteristics of non-carnivshyorous marsupials of the Santacrucian suggest tha t they lived

Mana Alejandro Abello et al

in forested habirats developed under warm temperatures and rain seasonality According to rhe foss il record of vascu lar plants the distribution of megathennal and mesothennal angiosperms expanded their distribution a t middle-high latitudes of Patagonia during the Late Oligocene to Early Miocene (Barreda and Palazzes i 2007 Brea et at ChapLer

7) Neveltheless the first records of some shrubby and herbaceous angiosperms in sou thern South America suggest that the vegetation acquired a more complex physiognomy than that of the Early Oli gocene (Barreda and Palazzesi

2007) During the Early Mi ocene xerophytic (or mesophyshytic) vascular plants were dominant in Patagonia and the development of all these specipoundllized comm unities was probshy

ably related to a wate r deficit in open forest regions or marginal marine areas During the late Early Miocene rainforest trees may have formed ripari an or ga llery forests in central Patagonia while drie r conditions would have

prevailed in lowlpoundl nd areas (Barreda and Palazzes i 2007) Finally during the latest Ea rl y Miocene xerophytic elemshyents suffered a geographic re tractio n in Patagonia wi th an increase of megathelmals and a dominance of aquatic he rbs

and hydrophytes Forests pers isted across extra-A ndean Patagonia until about the Midd le Miocene (BalTeda 2002 BaITeda and Palazzesi 2007 Palazzesi and Barreda 2007)

If we consider the ecological infonnation provided by al l the Santacrucian mammals (Prevos ti el al Chapter 11 Vizcaino el al Chapler 12 Bargo et aI Chapter 13 Cassini el al Chap ter 14 Candela el 01 Chapter 15 Kay et al C hapter J6) this fau na was dominated by grazers and

mixedmiddot feeders with frugivores and browsers remaining highly diverse This distribution of trophic niches indicates that during Santacrucipoundln times a balance existed between

grasslands and woodland~ probably represented by a park savanna (Webb 1978 Pascual and Ortiz-Iaureguizar 1990 Pascual er aI 1996 Orti z-Jaureg ui za r and Cladera 2006 and refe re nces therein ) From a climatic point o f view the presence of primates and othe r walm c1imare -sensiti ve vershy

te brates tha t have been recorded as far south as 5 1degS sugshygests that wann and forested habitats were well developed in Patagonia Nevertheless toget her wi th these indicators of waJm and forested habita ts there were also other mammals such as some rodents that indicate the existence o f open

habitats encroaching on areas of we t forests in Patagonia (Pascual el 0 1996 Ortiz-Jaureguizar and Cladera 2006 Perez 2010)

Considering the ev idence provided by vascular plants and mammals we may conclude that the ecological diversity of the Santpoundlcrucian marsupials is compatible with the exisl shyence of habi ta t pa tchiness during Santacrucian times with a

balance between closed and open habitats represented by u park savanna In this scenario the non-camivorous marsushypial species would have occupied the more forested area~ (Fig 107)

167 Paleoecology of Sa11lacrucian Paucilftberculata Gnd Microhiolheria

106 Conclusions Microbiorheria and Pallcituberculata of the Santa Cruz Fonnation constirute an ecologically diverse assemblage of non-carnivorous marupiats Among microbiotheriids we recoouize small insectivores such as MicroiJiorherium

c acieliia and M tehuelclwm and a medium-sized insectshyivore- frugivore M galegosel1se Compared with microshybiotheriids pauci ru bercuJalans are taxonom ically and ecologically more diverse hav ing a wider range or body mass and diet For rhis group we jdentify small ill~ctivores such as PhOl1ocdrOl11lfS gracilis medium-sized curso-saltashytorial insectivores such as PaJaeolhell les mintllUS (Fig 1O7b) and P lemoinei the small- to medium-sized inseclivoresshyfl1Jgivores Stilotherium dissimile and Aedesis owenii the medium-sized frugivore Abderite meridionais (Fig 107a)

and rhe large fl1J givore Palaeofhemes amtae Regarding the marsupials of the insectivore gu ild a minshy

imal niche overlap was inferred from differences in body mass and its relations 10 prey size and diet composition as is observed in ex tant insec ti vorous mammals ]n add ition (0

the inferred terresrrial curso-salta[Qria l locomotion of Palaeothellfes ml1uus and P lemoil1ei scansorial or arborshyeal locomotor behav iors could have evolved among nonshycarnivorous San lacrucian marsupials that allowed the ir ex ploitation of resources in the venical space

From the present study lhe ecological diversity of the non-camivorous Santacfllc ian marsupial indicates IJ1 al rhey lived in forested habitats under wanT temperatures aud rain seasonality Forested habitats could have supported rhe varied previollsly menrioued mar) upial niches offering diverse resources n the spatial and Irophic dimensions Considering also the paleoecologicltt l iuformation provided by vascu lar plants and al l the mammalian species we conshyclude rhat the ecological diversity of non-carn ivorous marshysupials is compatible with a patchy environment with a balance between vegeration typical of closed and open habitats rep resented by a park savanna

ACKNOW LE DG M EN T S We thank D Flores (MACN) A Kramarz (MACN) and M Reguero (MLP) for faci litating access to specimens of marsupials in their care and F Goin (MLP) for aJlowing us to srudy speci mens in his persona l collec tion Special thanks 10 rhe ed[Qrs of Ihis volume S F VizcaIno R F Kay and M S Bargo for inviting uS to make this cont ribution and 10 P Posadas (LASBEmiddotMLP) and C Morgan for their help with the English version Thi s is a contri bution to the projects PICT 0 143 to Sergio F Vizcaino and NSF 085 1272 0824546 to Richard F Kay

Appendix 101 Paucituberculata and Microbiotheria of the Santa Cruz Formation

Microbiolheria Ameghino 1889

Microbio the riidae Ameghino 1887 Microbiotheriwll acicula (Ameghino 189 1) Microbiolherium patagoniulln A meghino 1887 Microbiorherium teliuechum Ameghino 1887 Microbiorheriul7I gaegosense Sinclair 1906

Paucitubcrcu Lata Ameghino 1894

Caenolestidae Trouessart 1898 Srilolheriun1 dissimile Ameghino 1887 Pichipilidae (Marshall 1980) Phollocdromus gracilis Ameghino 1894 Palaeothe ntidae Sinclair J906 Palaeorhel1les oratae Ameghino J887 Palacothentes minutus Ameghino 1887 PalaeOlhenles intermedius Ameghino 1887 Palaeohemes lemoinei Ameghino 1887 Palaeothcmes pascuali Bown and Fleagle 1993 Aedestis owenii Ameghino 1887 Acdesris lemaird Bown and F1eagJe 1993 Abderiidae (Ameghino 1889) Abderites meridiollali Ameghino 1887

List of PoucililberclIlata and Microbiothaio from localities of the Santa Cruz Formation

For details of the specimens localities data of collection and collecors (Col) see Marshall (1980 1982) Bown and Fleagle (1993) and Vizcaino el 01 (Chaper I Figs 11 and 12 and Appendix ll)

Gobernador Gregores Acdesris owenii

Lago Cardiel Aedestis owenii

Rio C haJia - Ea Viven Aike - (Col Bown y R eagle) PaLaeothentes minulus Palaeoff1enres imermedills Aedestis owenii Aedestis lemairei

Monte Leon (Col Bown and Fleagle) Palaeolhenles ararae Palaeolhemes minltlJI Palaeothenles intermedius Palaeothentes emoinei Aedestit owenii Aedesis lemairei La Cueva (Col Ameghino) Phonocdromus gracilis Polaeothemes minUlus Poloeorhentes intermedius Polaeofhenres lemoinei Stilofherilll11 dissimile Ahderifes

meridiOlolis Microhiotherium pafOgonicllm M icrobiothershy

illm teIJelchwn

Yegua QueOlada (Col Ameghino) Palaeofhenles intermeshydius Palaeothcntes lemoinei MicroiJiolherillfrl tehuechwn

Saota Cruz (CoL Ameghino) PaaeOlhcn fes aratae Palaeolhenles minufus Palaeollientes lemoinei Microshy

biolherium pOlagoniclim

Monte Observacion (= Ceno ObservalOrio see Marshall 1976b and Vizcaino el al Chaper I Col Ameghino Bown and Fleagle) Palaeolhentes aralDe Paaeothentes minulUs Palacolhentes pascuali PalaeofJcmes intermedius PalaeOlhenres lemoinei Stilotheriwn dissimile Abderies merirlionaiis Acrlestis Olrenii Acdestis emairei Microbiofheriul11 aciclia Microbiohemiddotfum patagoniclIIn

Miclobiotheliul11 lehuelchurn

Puesto Estaucia La Costa (= Corriguen-Aike Col MLPshyDuke University) Palaeolhenles lemoinei Corriguen-Kaik (Col Ameghino) PalaeOlhe1les lemoinet Microbiotherium tehuelehwn

KilIik-Aike (Col H Felton) Polaeothentes minutus

Microbiorheriun1 tehuechum

Rio Gallegos (Col B Brown) PolOeOlhel1les aralae

Paiaeolhentes minuus

Near Feltou s Estaucia along the uorth bank of the RIo Gallegos (Col Bamum Brown) Phonocd()fllus gracilii

Microbiotheriwn adeula Microbiorherium gallegosense

Sehuen (= Rio Cllalia Col Ameghino) Palaeolhentcgt aratae Palaeofhellfes emoinei Palaeothenles intermedill Sriotherilllll dissimile AbderifeJ meridionalis Micra-shybiOff1erium patagonicllm

168

Appendix 102 Material studied

Microbiotheriidae

M icrobiofherillrn acicula (Arneghino 189 1) MACN-A 5727 a left mandibulm ramus with p3-m4 Horizon and locality Santa Cruz Formation Monte Obsershyvaci6n Santa Cruz Province

MicrohiOlherium palagonicIII1l Amegh illo J887 MLP 11-30 a right mandibul ar ramus wi th In 1-4 Horizon and locality Srulta Cruz Formation collected from laquolas barrancos del no Saila Cruz (Ameghino 1889 264) Santa Cruz Province

MicrobiOlherium felwechum Ameghino 1887 MLP 11-36 a right mandibul ru ramus with p2- m4 Horishy

zon and locality Santa Cruz FOlmation without locality data (see Marshall 1982) Santa Cruz Province

MicroNotherium gallegosense Sinclair 1906 AMNH 9591 a right mandibular ramu s with p3- m2 Horishyzon and locality Santa Cruz F0l111arion Es tancia Felton Santa Cruz Province

Dromiriops gliroides Thomas 1894 MACN 19142 MACN 2291 8 MACN 229 19 a nd MACN 13038

POlicilubercuata

Abderifes mcridionalis Ameghino 1887 MACN-A 5542 left mandibular ramus with m 1-4 and MACN-A 2037 left mandibular ramn s with p3- m4 HOli shyzan and locality SanLa Cruz Fonnation Monle Observashycion Santa Cruz Province MACN-A 5541 left mandibular ramus with p3-m4 and PU 15079 left mandibular ramus with p3- m3 HOlizon and locality Santa Cruz Fonnation Rio Chalia Santa Cruz Province MACN-A 8248 left mandibular ramus with p3-m3 HOlizon and locality Santa Cruz FOlmashyLion La Cueva Santa Cruz Province MACN-A 203 1 left mandibular ramus with rn2 MACN-A 2032 right mandjbular ramus with rn2-4 MACN -A 2033 right mandibular ramus with m2-4 MACN-A 2034 right mandibular ramus wirh ml - 3 MLP 11-109 rjght mandi bu lar ramus wilh m 1- 2 MLP 11 - 133 le ft mandibular ramus with m2- 3 MLP 55-XlJ- 13- 144 righ t mandibular ramus with m2 and MACN 1165 1 righL mandibular ralllus with p3-m4 Horizon and locality unknown Santa Cruz Province

169

Palacothclllcs minutus

MACN-A 56 19-5639a- l right and left mandibular rami with m3-4 di slal po rti on of right humerus proximal portion of right ulna partia ll y complete pelvis proximal ponion of right fe mur proximal portion of left femur and right calcaneum Ho ri zon and locality Santa Cruz Fo rmashyLion Killik-Aike Santa Cruz Prov ince

Palaeolhentes lemoinei

MPM-PV 3494 right mandi bu lar fragment wlth m2-4 and left edentulous mandibular fragment left humerus left ulna left fragment of pe lvis fragment of right tibia frag shyment of left tibia and right as tragalu s Horizon and locality Santa Cruz Formation Es tancia La Costa Member Fossil shyiferous Leve l 53 Pues to Estancia La Costa Santa Cmz Province

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moumai n pygmymiddotpogtsum (Bwrtlmys parvus) Victorian

Naturofisl89 10 1- 106 Dumont E R St rait S G and Frisc ia A R (2000) Abderit id

marsupials from the Miocene of Pmagonia an assess metU of form fUllct ion and evolution Journal oj Paleontology 74 11 6 1- 1172

Fisher DO and Dickman C R ( 1993) Body size- prey size relationships in insecti vorous marsupials tests of three hypotheses Ecology 74187 1- 1883

Flores O A (2006a ) Orden Paucilllberculata Ameghino 1894 In ManliJeros de Argen tina Sisremofica y Disrrihucufn ed R M Barquez M M Dlaz and R A Ojeda Tucuman SAREM p 45

Flores D A (2006b) Orden Microbio theria Amegh ino 1897

In MwmJeros de Argenrina Sistematica y Distrihucidn ed R M Barquez M M Dial and R A Ojeda Tucuman SAREM p 46

166

Species richness also tracks plant prodncri vity with higher productivity leading 0 more species (Kay el aI 1997)

Paleoenvi ronmental inferences can also be advanced by analyzing the trophic g uild slrUCl11re of Santacrucian marshysupials In a macroecologicai study of Neotropical marsushypials Birney and Monjeau (2003) evaluated the latitudinal

variation among several biological characters such as trophic guild structure habitat use and body size Taking into account that latitude is a surrogate fo r physical environshy

mental variables sucb as tempera ture and precipitation the trophic guild structure of Santacrucian marsllpials may offer clues to the Santacrucian paleoenvironments According to Birney and Monjeau (2003) three guilds were considered frugivores carnivores and insecti vores Current carnivorshyous marsupials include among othe rs the didelphids Didelphis LUfJeolino and Philander all o f them having

body masses less lhan 2 kg In the Sltt ntacruc ian assemblage ca ll1i vores with body masses less than or equal to 2 kg include the sparassodonts Sipaocyon gracilis Ameghino S obusfa Ameghino Pselldol1OiClis plisi llus Ameghino and Perarhereures pU118ens Ameghino (see Prevosti e al

Chapter I I) Thus smaJt carni vores represent 22 of the

Sanracrucian marsupia l species richness insectivore-frugishyvores plus frugivores 33 and insectivores 45 Comparshying the trophic g uild structure of Santacrucian marsupials with those of the modern Neol-ropics we find that in the Santacrucian fauna there is ltI relatively high percentage of frugivores in relation to camivores a ratio that occurs at low latitudes in the ex tant marsupial faunas of South Amershy

ica Birney and Monjeau (2003) concluded that the thelmal range (ie the difference between mean maximum extreme temperatures and mean minimum extreme temperatures) is the best predictor of the proporti on of frug ivores and camishyvores Closer to the equator the narrower thermal range allows year- long ava ilab ility of fmits and the percentage of

frug ivores is hig her lhan at high latitudes Additionall y differences in precipita tio n (ie seasonaJ ra infa ll) seem [ 0

be anothe r impo rta nt factor influe nc ing the abundance of frug ivores (Bimey and Monjeau 2003) If we cons ider this last factor the sharp differences between dry and wet season ~ in the tropics would have allowed more diversifishycalion in the trophic niche than more constan t precipitation

On the basis on these eco logical similarities we can infer that Santacl1lcian marsupia ls lived in relatively wann clishymates bUl with seasonal rainfall However it should he kept in mind that taphonomic bias and time averaging are common fac tors that affect the composition of fossil assemshy

blages Consequently in the absence of a precise evaluation of the incidence of these biases the infereuces derived from

a fossil assemblage have a less heuristic value that those based on living assemblages

In summary the ecological characteristics of non-carnivshyorous marsupials of the Santacrucian suggest tha t they lived

Mana Alejandro Abello et al

in forested habirats developed under warm temperatures and rain seasonality According to rhe foss il record of vascu lar plants the distribution of megathennal and mesothennal angiosperms expanded their distribution a t middle-high latitudes of Patagonia during the Late Oligocene to Early Miocene (Barreda and Palazzes i 2007 Brea et at ChapLer

7) Neveltheless the first records of some shrubby and herbaceous angiosperms in sou thern South America suggest that the vegetation acquired a more complex physiognomy than that of the Early Oli gocene (Barreda and Palazzesi

2007) During the Early Mi ocene xerophytic (or mesophyshytic) vascular plants were dominant in Patagonia and the development of all these specipoundllized comm unities was probshy

ably related to a wate r deficit in open forest regions or marginal marine areas During the late Early Miocene rainforest trees may have formed ripari an or ga llery forests in central Patagonia while drie r conditions would have

prevailed in lowlpoundl nd areas (Barreda and Palazzes i 2007) Finally during the latest Ea rl y Miocene xerophytic elemshyents suffered a geographic re tractio n in Patagonia wi th an increase of megathelmals and a dominance of aquatic he rbs

and hydrophytes Forests pers isted across extra-A ndean Patagonia until about the Midd le Miocene (BalTeda 2002 BaITeda and Palazzesi 2007 Palazzesi and Barreda 2007)

If we consider the ecological infonnation provided by al l the Santacrucian mammals (Prevos ti el al Chapter 11 Vizcaino el al Chapler 12 Bargo et aI Chapter 13 Cassini el al Chap ter 14 Candela el 01 Chapter 15 Kay et al C hapter J6) this fau na was dominated by grazers and

mixedmiddot feeders with frugivores and browsers remaining highly diverse This distribution of trophic niches indicates that during Santacrucipoundln times a balance existed between

grasslands and woodland~ probably represented by a park savanna (Webb 1978 Pascual and Ortiz-Iaureguizar 1990 Pascual er aI 1996 Orti z-Jaureg ui za r and Cladera 2006 and refe re nces therein ) From a climatic point o f view the presence of primates and othe r walm c1imare -sensiti ve vershy

te brates tha t have been recorded as far south as 5 1degS sugshygests that wann and forested habitats were well developed in Patagonia Nevertheless toget her wi th these indicators of waJm and forested habita ts there were also other mammals such as some rodents that indicate the existence o f open

habitats encroaching on areas of we t forests in Patagonia (Pascual el 0 1996 Ortiz-Jaureguizar and Cladera 2006 Perez 2010)

Considering the ev idence provided by vascular plants and mammals we may conclude that the ecological diversity of the Santpoundlcrucian marsupials is compatible with the exisl shyence of habi ta t pa tchiness during Santacrucian times with a

balance between closed and open habitats represented by u park savanna In this scenario the non-camivorous marsushypial species would have occupied the more forested area~ (Fig 107)

167 Paleoecology of Sa11lacrucian Paucilftberculata Gnd Microhiolheria

106 Conclusions Microbiorheria and Pallcituberculata of the Santa Cruz Fonnation constirute an ecologically diverse assemblage of non-carnivorous marupiats Among microbiotheriids we recoouize small insectivores such as MicroiJiorherium

c acieliia and M tehuelclwm and a medium-sized insectshyivore- frugivore M galegosel1se Compared with microshybiotheriids pauci ru bercuJalans are taxonom ically and ecologically more diverse hav ing a wider range or body mass and diet For rhis group we jdentify small ill~ctivores such as PhOl1ocdrOl11lfS gracilis medium-sized curso-saltashytorial insectivores such as PaJaeolhell les mintllUS (Fig 1O7b) and P lemoinei the small- to medium-sized inseclivoresshyfl1Jgivores Stilotherium dissimile and Aedesis owenii the medium-sized frugivore Abderite meridionais (Fig 107a)

and rhe large fl1J givore Palaeofhemes amtae Regarding the marsupials of the insectivore gu ild a minshy

imal niche overlap was inferred from differences in body mass and its relations 10 prey size and diet composition as is observed in ex tant insec ti vorous mammals ]n add ition (0

the inferred terresrrial curso-salta[Qria l locomotion of Palaeothellfes ml1uus and P lemoil1ei scansorial or arborshyeal locomotor behav iors could have evolved among nonshycarnivorous San lacrucian marsupials that allowed the ir ex ploitation of resources in the venical space

From the present study lhe ecological diversity of the non-camivorous Santacfllc ian marsupial indicates IJ1 al rhey lived in forested habitats under wanT temperatures aud rain seasonality Forested habitats could have supported rhe varied previollsly menrioued mar) upial niches offering diverse resources n the spatial and Irophic dimensions Considering also the paleoecologicltt l iuformation provided by vascu lar plants and al l the mammalian species we conshyclude rhat the ecological diversity of non-carn ivorous marshysupials is compatible with a patchy environment with a balance between vegeration typical of closed and open habitats rep resented by a park savanna

ACKNOW LE DG M EN T S We thank D Flores (MACN) A Kramarz (MACN) and M Reguero (MLP) for faci litating access to specimens of marsupials in their care and F Goin (MLP) for aJlowing us to srudy speci mens in his persona l collec tion Special thanks 10 rhe ed[Qrs of Ihis volume S F VizcaIno R F Kay and M S Bargo for inviting uS to make this cont ribution and 10 P Posadas (LASBEmiddotMLP) and C Morgan for their help with the English version Thi s is a contri bution to the projects PICT 0 143 to Sergio F Vizcaino and NSF 085 1272 0824546 to Richard F Kay

Appendix 101 Paucituberculata and Microbiotheria of the Santa Cruz Formation

Microbiolheria Ameghino 1889

Microbio the riidae Ameghino 1887 Microbiotheriwll acicula (Ameghino 189 1) Microbiolherium patagoniulln A meghino 1887 Microbiorherium teliuechum Ameghino 1887 Microbiorheriul7I gaegosense Sinclair 1906

Paucitubcrcu Lata Ameghino 1894

Caenolestidae Trouessart 1898 Srilolheriun1 dissimile Ameghino 1887 Pichipilidae (Marshall 1980) Phollocdromus gracilis Ameghino 1894 Palaeothe ntidae Sinclair J906 Palaeorhel1les oratae Ameghino J887 Palacothentes minutus Ameghino 1887 PalaeOlhenles intermedius Ameghino 1887 Palaeohemes lemoinei Ameghino 1887 Palaeothcmes pascuali Bown and Fleagle 1993 Aedestis owenii Ameghino 1887 Acdesris lemaird Bown and F1eagJe 1993 Abderiidae (Ameghino 1889) Abderites meridiollali Ameghino 1887

List of PoucililberclIlata and Microbiothaio from localities of the Santa Cruz Formation

For details of the specimens localities data of collection and collecors (Col) see Marshall (1980 1982) Bown and Fleagle (1993) and Vizcaino el 01 (Chaper I Figs 11 and 12 and Appendix ll)

Gobernador Gregores Acdesris owenii

Lago Cardiel Aedestis owenii

Rio C haJia - Ea Viven Aike - (Col Bown y R eagle) PaLaeothentes minulus Palaeoff1enres imermedills Aedestis owenii Aedestis lemairei

Monte Leon (Col Bown and Fleagle) Palaeolhenles ararae Palaeolhemes minltlJI Palaeothenles intermedius Palaeothentes emoinei Aedestit owenii Aedesis lemairei La Cueva (Col Ameghino) Phonocdromus gracilis Polaeothemes minUlus Poloeorhentes intermedius Polaeofhenres lemoinei Stilofherilll11 dissimile Ahderifes

meridiOlolis Microhiotherium pafOgonicllm M icrobiothershy

illm teIJelchwn

Yegua QueOlada (Col Ameghino) Palaeofhenles intermeshydius Palaeothcntes lemoinei MicroiJiolherillfrl tehuechwn

Saota Cruz (CoL Ameghino) PaaeOlhcn fes aratae Palaeolhenles minufus Palaeollientes lemoinei Microshy

biolherium pOlagoniclim

Monte Observacion (= Ceno ObservalOrio see Marshall 1976b and Vizcaino el al Chaper I Col Ameghino Bown and Fleagle) Palaeolhentes aralDe Paaeothentes minulUs Palacolhentes pascuali PalaeofJcmes intermedius PalaeOlhenres lemoinei Stilotheriwn dissimile Abderies merirlionaiis Acrlestis Olrenii Acdestis emairei Microbiofheriul11 aciclia Microbiohemiddotfum patagoniclIIn

Miclobiotheliul11 lehuelchurn

Puesto Estaucia La Costa (= Corriguen-Aike Col MLPshyDuke University) Palaeolhenles lemoinei Corriguen-Kaik (Col Ameghino) PalaeOlhe1les lemoinet Microbiotherium tehuelehwn

KilIik-Aike (Col H Felton) Polaeothentes minutus

Microbiorheriun1 tehuechum

Rio Gallegos (Col B Brown) PolOeOlhel1les aralae

Paiaeolhentes minuus

Near Feltou s Estaucia along the uorth bank of the RIo Gallegos (Col Bamum Brown) Phonocd()fllus gracilii

Microbiotheriwn adeula Microbiorherium gallegosense

Sehuen (= Rio Cllalia Col Ameghino) Palaeolhentcgt aratae Palaeofhellfes emoinei Palaeothenles intermedill Sriotherilllll dissimile AbderifeJ meridionalis Micra-shybiOff1erium patagonicllm

168

Appendix 102 Material studied

Microbiotheriidae

M icrobiofherillrn acicula (Arneghino 189 1) MACN-A 5727 a left mandibulm ramus with p3-m4 Horizon and locality Santa Cruz Formation Monte Obsershyvaci6n Santa Cruz Province

MicrohiOlherium palagonicIII1l Amegh illo J887 MLP 11-30 a right mandibul ar ramus wi th In 1-4 Horizon and locality Srulta Cruz Formation collected from laquolas barrancos del no Saila Cruz (Ameghino 1889 264) Santa Cruz Province

MicrobiOlherium felwechum Ameghino 1887 MLP 11-36 a right mandibul ru ramus with p2- m4 Horishy

zon and locality Santa Cruz FOlmation without locality data (see Marshall 1982) Santa Cruz Province

MicroNotherium gallegosense Sinclair 1906 AMNH 9591 a right mandibular ramu s with p3- m2 Horishyzon and locality Santa Cruz F0l111arion Es tancia Felton Santa Cruz Province

Dromiriops gliroides Thomas 1894 MACN 19142 MACN 2291 8 MACN 229 19 a nd MACN 13038

POlicilubercuata

Abderifes mcridionalis Ameghino 1887 MACN-A 5542 left mandibular ramus with m 1-4 and MACN-A 2037 left mandibular ramn s with p3- m4 HOli shyzan and locality SanLa Cruz Fonnation Monle Observashycion Santa Cruz Province MACN-A 5541 left mandibular ramus with p3-m4 and PU 15079 left mandibular ramus with p3- m3 HOlizon and locality Santa Cruz Fonnation Rio Chalia Santa Cruz Province MACN-A 8248 left mandibular ramus with p3-m3 HOlizon and locality Santa Cruz FOlmashyLion La Cueva Santa Cruz Province MACN-A 203 1 left mandibular ramus with rn2 MACN-A 2032 right mandjbular ramus with rn2-4 MACN -A 2033 right mandibular ramus with m2-4 MACN-A 2034 right mandibular ramus wirh ml - 3 MLP 11-109 rjght mandi bu lar ramus wilh m 1- 2 MLP 11 - 133 le ft mandibular ramus with m2- 3 MLP 55-XlJ- 13- 144 righ t mandibular ramus with m2 and MACN 1165 1 righL mandibular ralllus with p3-m4 Horizon and locality unknown Santa Cruz Province

169

Palacothclllcs minutus

MACN-A 56 19-5639a- l right and left mandibular rami with m3-4 di slal po rti on of right humerus proximal portion of right ulna partia ll y complete pelvis proximal ponion of right fe mur proximal portion of left femur and right calcaneum Ho ri zon and locality Santa Cruz Fo rmashyLion Killik-Aike Santa Cruz Prov ince

Palaeolhentes lemoinei

MPM-PV 3494 right mandi bu lar fragment wlth m2-4 and left edentulous mandibular fragment left humerus left ulna left fragment of pe lvis fragment of right tibia frag shyment of left tibia and right as tragalu s Horizon and locality Santa Cruz Formation Es tancia La Costa Member Fossil shyiferous Leve l 53 Pues to Estancia La Costa Santa Cmz Province

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marsupials from the Miocene of Pmagonia an assess metU of form fUllct ion and evolution Journal oj Paleontology 74 11 6 1- 1172

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167 Paleoecology of Sa11lacrucian Paucilftberculata Gnd Microhiolheria

106 Conclusions Microbiorheria and Pallcituberculata of the Santa Cruz Fonnation constirute an ecologically diverse assemblage of non-carnivorous marupiats Among microbiotheriids we recoouize small insectivores such as MicroiJiorherium

c acieliia and M tehuelclwm and a medium-sized insectshyivore- frugivore M galegosel1se Compared with microshybiotheriids pauci ru bercuJalans are taxonom ically and ecologically more diverse hav ing a wider range or body mass and diet For rhis group we jdentify small ill~ctivores such as PhOl1ocdrOl11lfS gracilis medium-sized curso-saltashytorial insectivores such as PaJaeolhell les mintllUS (Fig 1O7b) and P lemoinei the small- to medium-sized inseclivoresshyfl1Jgivores Stilotherium dissimile and Aedesis owenii the medium-sized frugivore Abderite meridionais (Fig 107a)

and rhe large fl1J givore Palaeofhemes amtae Regarding the marsupials of the insectivore gu ild a minshy

imal niche overlap was inferred from differences in body mass and its relations 10 prey size and diet composition as is observed in ex tant insec ti vorous mammals ]n add ition (0

the inferred terresrrial curso-salta[Qria l locomotion of Palaeothellfes ml1uus and P lemoil1ei scansorial or arborshyeal locomotor behav iors could have evolved among nonshycarnivorous San lacrucian marsupials that allowed the ir ex ploitation of resources in the venical space

From the present study lhe ecological diversity of the non-camivorous Santacfllc ian marsupial indicates IJ1 al rhey lived in forested habitats under wanT temperatures aud rain seasonality Forested habitats could have supported rhe varied previollsly menrioued mar) upial niches offering diverse resources n the spatial and Irophic dimensions Considering also the paleoecologicltt l iuformation provided by vascu lar plants and al l the mammalian species we conshyclude rhat the ecological diversity of non-carn ivorous marshysupials is compatible with a patchy environment with a balance between vegeration typical of closed and open habitats rep resented by a park savanna

ACKNOW LE DG M EN T S We thank D Flores (MACN) A Kramarz (MACN) and M Reguero (MLP) for faci litating access to specimens of marsupials in their care and F Goin (MLP) for aJlowing us to srudy speci mens in his persona l collec tion Special thanks 10 rhe ed[Qrs of Ihis volume S F VizcaIno R F Kay and M S Bargo for inviting uS to make this cont ribution and 10 P Posadas (LASBEmiddotMLP) and C Morgan for their help with the English version Thi s is a contri bution to the projects PICT 0 143 to Sergio F Vizcaino and NSF 085 1272 0824546 to Richard F Kay

Appendix 101 Paucituberculata and Microbiotheria of the Santa Cruz Formation

Microbiolheria Ameghino 1889

Microbio the riidae Ameghino 1887 Microbiotheriwll acicula (Ameghino 189 1) Microbiolherium patagoniulln A meghino 1887 Microbiorherium teliuechum Ameghino 1887 Microbiorheriul7I gaegosense Sinclair 1906

Paucitubcrcu Lata Ameghino 1894

Caenolestidae Trouessart 1898 Srilolheriun1 dissimile Ameghino 1887 Pichipilidae (Marshall 1980) Phollocdromus gracilis Ameghino 1894 Palaeothe ntidae Sinclair J906 Palaeorhel1les oratae Ameghino J887 Palacothentes minutus Ameghino 1887 PalaeOlhenles intermedius Ameghino 1887 Palaeohemes lemoinei Ameghino 1887 Palaeothcmes pascuali Bown and Fleagle 1993 Aedestis owenii Ameghino 1887 Acdesris lemaird Bown and F1eagJe 1993 Abderiidae (Ameghino 1889) Abderites meridiollali Ameghino 1887

List of PoucililberclIlata and Microbiothaio from localities of the Santa Cruz Formation

For details of the specimens localities data of collection and collecors (Col) see Marshall (1980 1982) Bown and Fleagle (1993) and Vizcaino el 01 (Chaper I Figs 11 and 12 and Appendix ll)

Gobernador Gregores Acdesris owenii

Lago Cardiel Aedestis owenii

Rio C haJia - Ea Viven Aike - (Col Bown y R eagle) PaLaeothentes minulus Palaeoff1enres imermedills Aedestis owenii Aedestis lemairei

Monte Leon (Col Bown and Fleagle) Palaeolhenles ararae Palaeolhemes minltlJI Palaeothenles intermedius Palaeothentes emoinei Aedestit owenii Aedesis lemairei La Cueva (Col Ameghino) Phonocdromus gracilis Polaeothemes minUlus Poloeorhentes intermedius Polaeofhenres lemoinei Stilofherilll11 dissimile Ahderifes

meridiOlolis Microhiotherium pafOgonicllm M icrobiothershy

illm teIJelchwn

Yegua QueOlada (Col Ameghino) Palaeofhenles intermeshydius Palaeothcntes lemoinei MicroiJiolherillfrl tehuechwn

Saota Cruz (CoL Ameghino) PaaeOlhcn fes aratae Palaeolhenles minufus Palaeollientes lemoinei Microshy

biolherium pOlagoniclim

Monte Observacion (= Ceno ObservalOrio see Marshall 1976b and Vizcaino el al Chaper I Col Ameghino Bown and Fleagle) Palaeolhentes aralDe Paaeothentes minulUs Palacolhentes pascuali PalaeofJcmes intermedius PalaeOlhenres lemoinei Stilotheriwn dissimile Abderies merirlionaiis Acrlestis Olrenii Acdestis emairei Microbiofheriul11 aciclia Microbiohemiddotfum patagoniclIIn

Miclobiotheliul11 lehuelchurn

Puesto Estaucia La Costa (= Corriguen-Aike Col MLPshyDuke University) Palaeolhenles lemoinei Corriguen-Kaik (Col Ameghino) PalaeOlhe1les lemoinet Microbiotherium tehuelehwn

KilIik-Aike (Col H Felton) Polaeothentes minutus

Microbiorheriun1 tehuechum

Rio Gallegos (Col B Brown) PolOeOlhel1les aralae

Paiaeolhentes minuus

Near Feltou s Estaucia along the uorth bank of the RIo Gallegos (Col Bamum Brown) Phonocd()fllus gracilii

Microbiotheriwn adeula Microbiorherium gallegosense

Sehuen (= Rio Cllalia Col Ameghino) Palaeolhentcgt aratae Palaeofhellfes emoinei Palaeothenles intermedill Sriotherilllll dissimile AbderifeJ meridionalis Micra-shybiOff1erium patagonicllm

168

Appendix 102 Material studied

Microbiotheriidae

M icrobiofherillrn acicula (Arneghino 189 1) MACN-A 5727 a left mandibulm ramus with p3-m4 Horizon and locality Santa Cruz Formation Monte Obsershyvaci6n Santa Cruz Province

MicrohiOlherium palagonicIII1l Amegh illo J887 MLP 11-30 a right mandibul ar ramus wi th In 1-4 Horizon and locality Srulta Cruz Formation collected from laquolas barrancos del no Saila Cruz (Ameghino 1889 264) Santa Cruz Province

MicrobiOlherium felwechum Ameghino 1887 MLP 11-36 a right mandibul ru ramus with p2- m4 Horishy

zon and locality Santa Cruz FOlmation without locality data (see Marshall 1982) Santa Cruz Province

MicroNotherium gallegosense Sinclair 1906 AMNH 9591 a right mandibular ramu s with p3- m2 Horishyzon and locality Santa Cruz F0l111arion Es tancia Felton Santa Cruz Province

Dromiriops gliroides Thomas 1894 MACN 19142 MACN 2291 8 MACN 229 19 a nd MACN 13038

POlicilubercuata

Abderifes mcridionalis Ameghino 1887 MACN-A 5542 left mandibular ramus with m 1-4 and MACN-A 2037 left mandibular ramn s with p3- m4 HOli shyzan and locality SanLa Cruz Fonnation Monle Observashycion Santa Cruz Province MACN-A 5541 left mandibular ramus with p3-m4 and PU 15079 left mandibular ramus with p3- m3 HOlizon and locality Santa Cruz Fonnation Rio Chalia Santa Cruz Province MACN-A 8248 left mandibular ramus with p3-m3 HOlizon and locality Santa Cruz FOlmashyLion La Cueva Santa Cruz Province MACN-A 203 1 left mandibular ramus with rn2 MACN-A 2032 right mandjbular ramus with rn2-4 MACN -A 2033 right mandibular ramus with m2-4 MACN-A 2034 right mandibular ramus wirh ml - 3 MLP 11-109 rjght mandi bu lar ramus wilh m 1- 2 MLP 11 - 133 le ft mandibular ramus with m2- 3 MLP 55-XlJ- 13- 144 righ t mandibular ramus with m2 and MACN 1165 1 righL mandibular ralllus with p3-m4 Horizon and locality unknown Santa Cruz Province

169

Palacothclllcs minutus

MACN-A 56 19-5639a- l right and left mandibular rami with m3-4 di slal po rti on of right humerus proximal portion of right ulna partia ll y complete pelvis proximal ponion of right fe mur proximal portion of left femur and right calcaneum Ho ri zon and locality Santa Cruz Fo rmashyLion Killik-Aike Santa Cruz Prov ince

Palaeolhentes lemoinei

MPM-PV 3494 right mandi bu lar fragment wlth m2-4 and left edentulous mandibular fragment left humerus left ulna left fragment of pe lvis fragment of right tibia frag shyment of left tibia and right as tragalu s Horizon and locality Santa Cruz Formation Es tancia La Costa Member Fossil shyiferous Leve l 53 Pues to Estancia La Costa Santa Cmz Province

REFERE N CES

Abe Jo M A (20C)) Sistematica y bioeslrmigrafia de los

Pallc ilubercul ata (Mammllia Mltl rsupialia) del Cenozoico de Ame nca de l Sur Unpubli shed PhD lhesis Univers idad

Nac ional de La Pima ArgelHina Abe llo M A md Candela A M (20 10) Poslcranial skeleLOn

of Ule Miocene marsupia l Palaeolhcmes (paucituberculata

Palaeothemidae) pa leobiology lind phylogeny Jnulllol of

Vertehrate Paleonfology 301 515- 1527 Abello M A and Rubilar-Rogers D (in pre-Ss) Revision de l

genera Ahderles Arneghino 1887 (Marsupialia

Paucimbercu]lt11a) Ameghinirll1o

Albuja L and Pallerson B D (JcY6) A new species or northem shrew-opossum (Pa uc itnbercul ata Caenolestidae) from the Cordillera del Condor Ecuador Journal ofMammaogy

77 4t-53 Ameghino F (1887) Enumeracion sistema tica de las especies de

mamfferos fos iles co lecc ionados POI Carlos Ameghino en los ten-enos eocenos de la Patagonia austral Bolelln del MlHeo de La Plata 1 1-26

Ameghino F ( 1889) Contribucion al conoc imienlO de los mamiferos fosiles de la Repub lica Argentina Aetas de fa Academia Nacional de Ciellcias de Cordoha 6

XXXIII-t On Ameghino F ( 189 1) Nuevos restos de mamiferos fos ilcs

descubierLmi por Carlos Ameghino en e t Eoceno inferior de Patagonia austral Especies nuevac adi ciones y

170 MarLa Alejandro Abello el al

correcciones Revisra Argemina de His(oria Natural

1289-328 Amico G C Rodriguez~Cabal M A and Aizen M A (2009)

The pOlenrial key seedmiddotdispers ing role of the arboreal marsupia l Dlomiciops gliroides Acta Oemlogica 35 8- 13

Amrine-Madsen H Scall y M Westerman M et al (2003) Nuclear gene sequences prov ide ev idence for the monophyly of a llstraiide iphian marsupials Molecular

Phylogenclics alld Evolution 28 186-196 Anderson S (1997) Mammals of Bolivia taxonomy and

distribulion Bulletin oj he American Mlfseum of Naural Hisory 231 1--652

A rgot C (2003a) POHcranial functional adaptarions in the South

American Miocene borhyaenoids (Mammalia Meta theria) Cladosicfis PseudoJloliclis and Sipalocyoll Alcheringa

27 303- 356 Argot C (2003b) Funclional adaplalions of (he poslcrania l

ske lelon o f two Miocene borh yaenoids (Mammalia Mela lheria) Borhyo(lfa and Profhyloeitlus from 50mh

America Palaeontology 46 12 13- l267 Asher RI Horovitz I and SanchelmiddotViliagra MR (2004)

First combined cladistic analysis of marsupi al mammal int erre l at i on ~h ips Molecular Phylogenetics ol1d Evolution

33 240-250 August P v (1983) The role of habital complexilY and

heterogeneity in struclUring tropical mammal communities

Ecology 64 (6) 1495- 1507 Bakker V J and Kelt D A (2000) Scale-dependenr pattems in

body size dis tribut ions of Neorropical mammals Ecology 81 3530-3547

Barkley L J and Whitaker 1 O Jr (1 984) Confinnmion of Caellolestes in Peru with in format ion on diet Journal oj

Mamrrwlogy 65 328-330 Barreda V D (2002) Palinofloras cenozoicas In Geologia )

Recttlsos NafJr(lles de Sallfa Cruz Refatoio del XV COllgreso Geologico Argentlnu ed MJ Haller Buenos Aires Asociaci6n Geol6g ica Argentina pp 545- 567

Barreda V and Palazlesi L (2007) Patagonian vegetation turnovers during the Paleogene-earJy Neoge ne origin of arid-adapted flo ras The Botanical Relliew 73 31- 50

Beck R M D (2008) A dated phylogeny o f marsupials us ing ltl molecular supelmarix and muhiple foss il constrainls

Journal ofMammolo~) 89 175- 119 Birney pound C and Monjeau 1 A (2001) Latitud inal variation

in Soulh American marsupial bio logy In Predators with pouches the biology oj COllil0101I5 marsupials ed M Jones C Dickman and M AcheI Hoban Australia

CSJRO Pub li shing pp 297- 3 17 Bimey E C Sikes R S Monjeau 1 A Guthmann N and

Cltlrleton 1 P (J996) Comments on Paragonian marsupials of Argentina In CClfl lrihllf ioll in ManUwfogy A Memorial Volume Honoring Dr I Knox Jones Jr_ ed H H

Genoways aud R 1 Baker Museum of Texas Tech

Un iversity Press pp t49- J54 Bown T M and F leagle J G (1993) Sysrematics biostratigraphy

and dental evo lution of the Palaeothentidae later Oligocene

to Early- Middle Miocene (Deseadan-Sanacrucian)

Caenolesto id Marsupials of South America Journal oj Poaeolrolog) Memoir 29 67 1-76

Bozinovic F Ruiz G and Rosentnann M (2004) Energerics and torpor of a SOLl th American li ving fossil the

microbiolheriid Dromiciops gliroides Journal oj Comparafive Physiology B 174 293-297

Charles-Dominique P (1983) Eco logy and social

adaptalion in didelphid marsup ials comparisons with eUlherians of simila r eco logy In AdlGl1ces in the

Study of Mammalian Bellmior ed 1 F Eisenberg ShippenSburg Ame rican Society of Mammalogist pp 305-422

CharlesmiddotOominique P Atramenrowicz M Charles-Dominique M el at (1981) Les mammiferes frugi vo res arboricoles noctulT1es d une forel guyanaise inleH e la rions plantesshyan imaux Revue d Ecologie (Terre Vie) 35 341--436

Churchfield S and Shefte l B1 ( 1994) Food niche overlap and ecologica l se parat ion in a multi-species community of shrews in the Siberian laiga1ournal of Zoology 234 105- 124

Churchtie ld S bull Nesterenko V A and Shvarts E A (1999) Food niche overlap and ecologica l separalion amongst six species of coexisting forest shrews (lnsecllvora

Soricidae) in the Russian Far East Jowna of Zoo[oy

248 349- 359 Croft D B and Eisenberg J F (2006) Behaviour In Marsupials

ed P J Armall C R Dickman and I D Hume Cambridge

UK Cambridge UniversiTY Press pp 229- 298 Delciellos A C and Vieira M V (2006) Arboreal walking

performance in seven didelphid marsupials as an aspect

of their fundamental niche AlJsfral Ecg 31 449--457 DeicielJos A C and Vieira M V (2009) Jumping ability

in the arboreal locomotion of didelphid marsupials MasfOzoologlo Neorropical 16 299- 307

Dickman C R and Vieira E (2006) Ecology and life histories In Malwpias ed 1 P Armal i C R Dickman and L D

Hume Cambridge Cambridge University Press

pp 199-228 Dimpel H and Calaby J H (1972) FUllher observaTions on the

moumai n pygmymiddotpogtsum (Bwrtlmys parvus) Victorian

Naturofisl89 10 1- 106 Dumont E R St rait S G and Frisc ia A R (2000) Abderit id

marsupials from the Miocene of Pmagonia an assess metU of form fUllct ion and evolution Journal oj Paleontology 74 11 6 1- 1172

Fisher DO and Dickman C R ( 1993) Body size- prey size relationships in insecti vorous marsupials tests of three hypotheses Ecology 74187 1- 1883

Flores O A (2006a ) Orden Paucilllberculata Ameghino 1894 In ManliJeros de Argen tina Sisremofica y Disrrihucufn ed R M Barquez M M Dlaz and R A Ojeda Tucuman SAREM p 45

Flores D A (2006b) Orden Microbio theria Amegh ino 1897

In MwmJeros de Argenrina Sistematica y Distrihucidn ed R M Barquez M M Dial and R A Ojeda Tucuman SAREM p 46

Appendix 101 Paucituberculata and Microbiotheria of the Santa Cruz Formation

Microbiolheria Ameghino 1889

Microbio the riidae Ameghino 1887 Microbiotheriwll acicula (Ameghino 189 1) Microbiolherium patagoniulln A meghino 1887 Microbiorherium teliuechum Ameghino 1887 Microbiorheriul7I gaegosense Sinclair 1906

Paucitubcrcu Lata Ameghino 1894

Caenolestidae Trouessart 1898 Srilolheriun1 dissimile Ameghino 1887 Pichipilidae (Marshall 1980) Phollocdromus gracilis Ameghino 1894 Palaeothe ntidae Sinclair J906 Palaeorhel1les oratae Ameghino J887 Palacothentes minutus Ameghino 1887 PalaeOlhenles intermedius Ameghino 1887 Palaeohemes lemoinei Ameghino 1887 Palaeothcmes pascuali Bown and Fleagle 1993 Aedestis owenii Ameghino 1887 Acdesris lemaird Bown and F1eagJe 1993 Abderiidae (Ameghino 1889) Abderites meridiollali Ameghino 1887

List of PoucililberclIlata and Microbiothaio from localities of the Santa Cruz Formation

For details of the specimens localities data of collection and collecors (Col) see Marshall (1980 1982) Bown and Fleagle (1993) and Vizcaino el 01 (Chaper I Figs 11 and 12 and Appendix ll)

Gobernador Gregores Acdesris owenii

Lago Cardiel Aedestis owenii

Rio C haJia - Ea Viven Aike - (Col Bown y R eagle) PaLaeothentes minulus Palaeoff1enres imermedills Aedestis owenii Aedestis lemairei

Monte Leon (Col Bown and Fleagle) Palaeolhenles ararae Palaeolhemes minltlJI Palaeothenles intermedius Palaeothentes emoinei Aedestit owenii Aedesis lemairei La Cueva (Col Ameghino) Phonocdromus gracilis Polaeothemes minUlus Poloeorhentes intermedius Polaeofhenres lemoinei Stilofherilll11 dissimile Ahderifes

meridiOlolis Microhiotherium pafOgonicllm M icrobiothershy

illm teIJelchwn

Yegua QueOlada (Col Ameghino) Palaeofhenles intermeshydius Palaeothcntes lemoinei MicroiJiolherillfrl tehuechwn

Saota Cruz (CoL Ameghino) PaaeOlhcn fes aratae Palaeolhenles minufus Palaeollientes lemoinei Microshy

biolherium pOlagoniclim

Monte Observacion (= Ceno ObservalOrio see Marshall 1976b and Vizcaino el al Chaper I Col Ameghino Bown and Fleagle) Palaeolhentes aralDe Paaeothentes minulUs Palacolhentes pascuali PalaeofJcmes intermedius PalaeOlhenres lemoinei Stilotheriwn dissimile Abderies merirlionaiis Acrlestis Olrenii Acdestis emairei Microbiofheriul11 aciclia Microbiohemiddotfum patagoniclIIn

Miclobiotheliul11 lehuelchurn

Puesto Estaucia La Costa (= Corriguen-Aike Col MLPshyDuke University) Palaeolhenles lemoinei Corriguen-Kaik (Col Ameghino) PalaeOlhe1les lemoinet Microbiotherium tehuelehwn

KilIik-Aike (Col H Felton) Polaeothentes minutus

Microbiorheriun1 tehuechum

Rio Gallegos (Col B Brown) PolOeOlhel1les aralae

Paiaeolhentes minuus

Near Feltou s Estaucia along the uorth bank of the RIo Gallegos (Col Bamum Brown) Phonocd()fllus gracilii

Microbiotheriwn adeula Microbiorherium gallegosense

Sehuen (= Rio Cllalia Col Ameghino) Palaeolhentcgt aratae Palaeofhellfes emoinei Palaeothenles intermedill Sriotherilllll dissimile AbderifeJ meridionalis Micra-shybiOff1erium patagonicllm

168

Appendix 102 Material studied

Microbiotheriidae

M icrobiofherillrn acicula (Arneghino 189 1) MACN-A 5727 a left mandibulm ramus with p3-m4 Horizon and locality Santa Cruz Formation Monte Obsershyvaci6n Santa Cruz Province

MicrohiOlherium palagonicIII1l Amegh illo J887 MLP 11-30 a right mandibul ar ramus wi th In 1-4 Horizon and locality Srulta Cruz Formation collected from laquolas barrancos del no Saila Cruz (Ameghino 1889 264) Santa Cruz Province

MicrobiOlherium felwechum Ameghino 1887 MLP 11-36 a right mandibul ru ramus with p2- m4 Horishy

zon and locality Santa Cruz FOlmation without locality data (see Marshall 1982) Santa Cruz Province

MicroNotherium gallegosense Sinclair 1906 AMNH 9591 a right mandibular ramu s with p3- m2 Horishyzon and locality Santa Cruz F0l111arion Es tancia Felton Santa Cruz Province

Dromiriops gliroides Thomas 1894 MACN 19142 MACN 2291 8 MACN 229 19 a nd MACN 13038

POlicilubercuata

Abderifes mcridionalis Ameghino 1887 MACN-A 5542 left mandibular ramus with m 1-4 and MACN-A 2037 left mandibular ramn s with p3- m4 HOli shyzan and locality SanLa Cruz Fonnation Monle Observashycion Santa Cruz Province MACN-A 5541 left mandibular ramus with p3-m4 and PU 15079 left mandibular ramus with p3- m3 HOlizon and locality Santa Cruz Fonnation Rio Chalia Santa Cruz Province MACN-A 8248 left mandibular ramus with p3-m3 HOlizon and locality Santa Cruz FOlmashyLion La Cueva Santa Cruz Province MACN-A 203 1 left mandibular ramus with rn2 MACN-A 2032 right mandjbular ramus with rn2-4 MACN -A 2033 right mandibular ramus with m2-4 MACN-A 2034 right mandibular ramus wirh ml - 3 MLP 11-109 rjght mandi bu lar ramus wilh m 1- 2 MLP 11 - 133 le ft mandibular ramus with m2- 3 MLP 55-XlJ- 13- 144 righ t mandibular ramus with m2 and MACN 1165 1 righL mandibular ralllus with p3-m4 Horizon and locality unknown Santa Cruz Province

169

Palacothclllcs minutus

MACN-A 56 19-5639a- l right and left mandibular rami with m3-4 di slal po rti on of right humerus proximal portion of right ulna partia ll y complete pelvis proximal ponion of right fe mur proximal portion of left femur and right calcaneum Ho ri zon and locality Santa Cruz Fo rmashyLion Killik-Aike Santa Cruz Prov ince

Palaeolhentes lemoinei

MPM-PV 3494 right mandi bu lar fragment wlth m2-4 and left edentulous mandibular fragment left humerus left ulna left fragment of pe lvis fragment of right tibia frag shyment of left tibia and right as tragalu s Horizon and locality Santa Cruz Formation Es tancia La Costa Member Fossil shyiferous Leve l 53 Pues to Estancia La Costa Santa Cmz Province

REFERE N CES

Abe Jo M A (20C)) Sistematica y bioeslrmigrafia de los

Pallc ilubercul ata (Mammllia Mltl rsupialia) del Cenozoico de Ame nca de l Sur Unpubli shed PhD lhesis Univers idad

Nac ional de La Pima ArgelHina Abe llo M A md Candela A M (20 10) Poslcranial skeleLOn

of Ule Miocene marsupia l Palaeolhcmes (paucituberculata

Palaeothemidae) pa leobiology lind phylogeny Jnulllol of

Vertehrate Paleonfology 301 515- 1527 Abello M A and Rubilar-Rogers D (in pre-Ss) Revision de l

genera Ahderles Arneghino 1887 (Marsupialia

Paucimbercu]lt11a) Ameghinirll1o

Albuja L and Pallerson B D (JcY6) A new species or northem shrew-opossum (Pa uc itnbercul ata Caenolestidae) from the Cordillera del Condor Ecuador Journal ofMammaogy

77 4t-53 Ameghino F (1887) Enumeracion sistema tica de las especies de

mamfferos fos iles co lecc ionados POI Carlos Ameghino en los ten-enos eocenos de la Patagonia austral Bolelln del MlHeo de La Plata 1 1-26

Ameghino F ( 1889) Contribucion al conoc imienlO de los mamiferos fosiles de la Repub lica Argentina Aetas de fa Academia Nacional de Ciellcias de Cordoha 6

XXXIII-t On Ameghino F ( 189 1) Nuevos restos de mamiferos fos ilcs

descubierLmi por Carlos Ameghino en e t Eoceno inferior de Patagonia austral Especies nuevac adi ciones y

170 MarLa Alejandro Abello el al

correcciones Revisra Argemina de His(oria Natural

1289-328 Amico G C Rodriguez~Cabal M A and Aizen M A (2009)

The pOlenrial key seedmiddotdispers ing role of the arboreal marsupia l Dlomiciops gliroides Acta Oemlogica 35 8- 13

Amrine-Madsen H Scall y M Westerman M et al (2003) Nuclear gene sequences prov ide ev idence for the monophyly of a llstraiide iphian marsupials Molecular

Phylogenclics alld Evolution 28 186-196 Anderson S (1997) Mammals of Bolivia taxonomy and

distribulion Bulletin oj he American Mlfseum of Naural Hisory 231 1--652

A rgot C (2003a) POHcranial functional adaptarions in the South

American Miocene borhyaenoids (Mammalia Meta theria) Cladosicfis PseudoJloliclis and Sipalocyoll Alcheringa

27 303- 356 Argot C (2003b) Funclional adaplalions of (he poslcrania l

ske lelon o f two Miocene borh yaenoids (Mammalia Mela lheria) Borhyo(lfa and Profhyloeitlus from 50mh

America Palaeontology 46 12 13- l267 Asher RI Horovitz I and SanchelmiddotViliagra MR (2004)

First combined cladistic analysis of marsupi al mammal int erre l at i on ~h ips Molecular Phylogenetics ol1d Evolution

33 240-250 August P v (1983) The role of habital complexilY and

heterogeneity in struclUring tropical mammal communities

Ecology 64 (6) 1495- 1507 Bakker V J and Kelt D A (2000) Scale-dependenr pattems in

body size dis tribut ions of Neorropical mammals Ecology 81 3530-3547

Barkley L J and Whitaker 1 O Jr (1 984) Confinnmion of Caellolestes in Peru with in format ion on diet Journal oj

Mamrrwlogy 65 328-330 Barreda V D (2002) Palinofloras cenozoicas In Geologia )

Recttlsos NafJr(lles de Sallfa Cruz Refatoio del XV COllgreso Geologico Argentlnu ed MJ Haller Buenos Aires Asociaci6n Geol6g ica Argentina pp 545- 567

Barreda V and Palazlesi L (2007) Patagonian vegetation turnovers during the Paleogene-earJy Neoge ne origin of arid-adapted flo ras The Botanical Relliew 73 31- 50

Beck R M D (2008) A dated phylogeny o f marsupials us ing ltl molecular supelmarix and muhiple foss il constrainls

Journal ofMammolo~) 89 175- 119 Birney pound C and Monjeau 1 A (2001) Latitud inal variation

in Soulh American marsupial bio logy In Predators with pouches the biology oj COllil0101I5 marsupials ed M Jones C Dickman and M AcheI Hoban Australia

CSJRO Pub li shing pp 297- 3 17 Bimey E C Sikes R S Monjeau 1 A Guthmann N and

Cltlrleton 1 P (J996) Comments on Paragonian marsupials of Argentina In CClfl lrihllf ioll in ManUwfogy A Memorial Volume Honoring Dr I Knox Jones Jr_ ed H H

Genoways aud R 1 Baker Museum of Texas Tech

Un iversity Press pp t49- J54 Bown T M and F leagle J G (1993) Sysrematics biostratigraphy

and dental evo lution of the Palaeothentidae later Oligocene

to Early- Middle Miocene (Deseadan-Sanacrucian)

Caenolesto id Marsupials of South America Journal oj Poaeolrolog) Memoir 29 67 1-76

Bozinovic F Ruiz G and Rosentnann M (2004) Energerics and torpor of a SOLl th American li ving fossil the

microbiolheriid Dromiciops gliroides Journal oj Comparafive Physiology B 174 293-297

Charles-Dominique P (1983) Eco logy and social

adaptalion in didelphid marsup ials comparisons with eUlherians of simila r eco logy In AdlGl1ces in the

Study of Mammalian Bellmior ed 1 F Eisenberg ShippenSburg Ame rican Society of Mammalogist pp 305-422

CharlesmiddotOominique P Atramenrowicz M Charles-Dominique M el at (1981) Les mammiferes frugi vo res arboricoles noctulT1es d une forel guyanaise inleH e la rions plantesshyan imaux Revue d Ecologie (Terre Vie) 35 341--436

Churchfield S and Shefte l B1 ( 1994) Food niche overlap and ecologica l se parat ion in a multi-species community of shrews in the Siberian laiga1ournal of Zoology 234 105- 124

Churchtie ld S bull Nesterenko V A and Shvarts E A (1999) Food niche overlap and ecologica l separalion amongst six species of coexisting forest shrews (lnsecllvora

Soricidae) in the Russian Far East Jowna of Zoo[oy

248 349- 359 Croft D B and Eisenberg J F (2006) Behaviour In Marsupials

ed P J Armall C R Dickman and I D Hume Cambridge

UK Cambridge UniversiTY Press pp 229- 298 Delciellos A C and Vieira M V (2006) Arboreal walking

performance in seven didelphid marsupials as an aspect

of their fundamental niche AlJsfral Ecg 31 449--457 DeicielJos A C and Vieira M V (2009) Jumping ability

in the arboreal locomotion of didelphid marsupials MasfOzoologlo Neorropical 16 299- 307

Dickman C R and Vieira E (2006) Ecology and life histories In Malwpias ed 1 P Armal i C R Dickman and L D

Hume Cambridge Cambridge University Press

pp 199-228 Dimpel H and Calaby J H (1972) FUllher observaTions on the

moumai n pygmymiddotpogtsum (Bwrtlmys parvus) Victorian

Naturofisl89 10 1- 106 Dumont E R St rait S G and Frisc ia A R (2000) Abderit id

marsupials from the Miocene of Pmagonia an assess metU of form fUllct ion and evolution Journal oj Paleontology 74 11 6 1- 1172

Fisher DO and Dickman C R ( 1993) Body size- prey size relationships in insecti vorous marsupials tests of three hypotheses Ecology 74187 1- 1883

Flores O A (2006a ) Orden Paucilllberculata Ameghino 1894 In ManliJeros de Argen tina Sisremofica y Disrrihucufn ed R M Barquez M M Dlaz and R A Ojeda Tucuman SAREM p 45

Flores D A (2006b) Orden Microbio theria Amegh ino 1897

In MwmJeros de Argenrina Sistematica y Distrihucidn ed R M Barquez M M Dial and R A Ojeda Tucuman SAREM p 46

Appendix 102 Material studied

Microbiotheriidae

M icrobiofherillrn acicula (Arneghino 189 1) MACN-A 5727 a left mandibulm ramus with p3-m4 Horizon and locality Santa Cruz Formation Monte Obsershyvaci6n Santa Cruz Province

MicrohiOlherium palagonicIII1l Amegh illo J887 MLP 11-30 a right mandibul ar ramus wi th In 1-4 Horizon and locality Srulta Cruz Formation collected from laquolas barrancos del no Saila Cruz (Ameghino 1889 264) Santa Cruz Province

MicrobiOlherium felwechum Ameghino 1887 MLP 11-36 a right mandibul ru ramus with p2- m4 Horishy

zon and locality Santa Cruz FOlmation without locality data (see Marshall 1982) Santa Cruz Province

MicroNotherium gallegosense Sinclair 1906 AMNH 9591 a right mandibular ramu s with p3- m2 Horishyzon and locality Santa Cruz F0l111arion Es tancia Felton Santa Cruz Province

Dromiriops gliroides Thomas 1894 MACN 19142 MACN 2291 8 MACN 229 19 a nd MACN 13038

POlicilubercuata

Abderifes mcridionalis Ameghino 1887 MACN-A 5542 left mandibular ramus with m 1-4 and MACN-A 2037 left mandibular ramn s with p3- m4 HOli shyzan and locality SanLa Cruz Fonnation Monle Observashycion Santa Cruz Province MACN-A 5541 left mandibular ramus with p3-m4 and PU 15079 left mandibular ramus with p3- m3 HOlizon and locality Santa Cruz Fonnation Rio Chalia Santa Cruz Province MACN-A 8248 left mandibular ramus with p3-m3 HOlizon and locality Santa Cruz FOlmashyLion La Cueva Santa Cruz Province MACN-A 203 1 left mandibular ramus with rn2 MACN-A 2032 right mandjbular ramus with rn2-4 MACN -A 2033 right mandibular ramus with m2-4 MACN-A 2034 right mandibular ramus wirh ml - 3 MLP 11-109 rjght mandi bu lar ramus wilh m 1- 2 MLP 11 - 133 le ft mandibular ramus with m2- 3 MLP 55-XlJ- 13- 144 righ t mandibular ramus with m2 and MACN 1165 1 righL mandibular ralllus with p3-m4 Horizon and locality unknown Santa Cruz Province

169

Palacothclllcs minutus

MACN-A 56 19-5639a- l right and left mandibular rami with m3-4 di slal po rti on of right humerus proximal portion of right ulna partia ll y complete pelvis proximal ponion of right fe mur proximal portion of left femur and right calcaneum Ho ri zon and locality Santa Cruz Fo rmashyLion Killik-Aike Santa Cruz Prov ince

Palaeolhentes lemoinei

MPM-PV 3494 right mandi bu lar fragment wlth m2-4 and left edentulous mandibular fragment left humerus left ulna left fragment of pe lvis fragment of right tibia frag shyment of left tibia and right as tragalu s Horizon and locality Santa Cruz Formation Es tancia La Costa Member Fossil shyiferous Leve l 53 Pues to Estancia La Costa Santa Cmz Province

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Phylogenclics alld Evolution 28 186-196 Anderson S (1997) Mammals of Bolivia taxonomy and

distribulion Bulletin oj he American Mlfseum of Naural Hisory 231 1--652

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American Miocene borhyaenoids (Mammalia Meta theria) Cladosicfis PseudoJloliclis and Sipalocyoll Alcheringa

27 303- 356 Argot C (2003b) Funclional adaplalions of (he poslcrania l

ske lelon o f two Miocene borh yaenoids (Mammalia Mela lheria) Borhyo(lfa and Profhyloeitlus from 50mh

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microbiolheriid Dromiciops gliroides Journal oj Comparafive Physiology B 174 293-297

Charles-Dominique P (1983) Eco logy and social

adaptalion in didelphid marsup ials comparisons with eUlherians of simila r eco logy In AdlGl1ces in the

Study of Mammalian Bellmior ed 1 F Eisenberg ShippenSburg Ame rican Society of Mammalogist pp 305-422

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Churchfield S and Shefte l B1 ( 1994) Food niche overlap and ecologica l se parat ion in a multi-species community of shrews in the Siberian laiga1ournal of Zoology 234 105- 124

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Soricidae) in the Russian Far East Jowna of Zoo[oy

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in the arboreal locomotion of didelphid marsupials MasfOzoologlo Neorropical 16 299- 307

Dickman C R and Vieira E (2006) Ecology and life histories In Malwpias ed 1 P Armal i C R Dickman and L D

Hume Cambridge Cambridge University Press

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Fisher DO and Dickman C R ( 1993) Body size- prey size relationships in insecti vorous marsupials tests of three hypotheses Ecology 74187 1- 1883

Flores O A (2006a ) Orden Paucilllberculata Ameghino 1894 In ManliJeros de Argen tina Sisremofica y Disrrihucufn ed R M Barquez M M Dlaz and R A Ojeda Tucuman SAREM p 45

Flores D A (2006b) Orden Microbio theria Amegh ino 1897

In MwmJeros de Argenrina Sistematica y Distrihucidn ed R M Barquez M M Dial and R A Ojeda Tucuman SAREM p 46

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