the eocene to pleistocene vertebrates of bolivia and their...

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THE EOCENE TO PLEISTOCENE VERTEBRATES OF BOLIVIA AND THEIR STRATIGRAPHIC CONTEXT

A REVIEW

LARRY G. MARSHALL" & THIERRY SEMPERE** * Institute of Human Origins, 2453 Ridge Road, Berkeley, California 94709, U.S.A.

** Orstom, UR lH, Casilla 4875, Santa Cruz de la Sierra, Bolivia. Present address: Centre de Géologie Générale et Minibre, Ecole des Mines, 35 rue Saint Honor& 77305 Fontainebleau, France

INTRODUCTION

The record of Cenozoic fossil vertebrates in Bolivia is extremely good. Compared with other countries in South America, Bolivia is second only to Argentina in the number of known localities and in the wealth of taxa.

Of the different vertebrate groups, the mammals are by far the most abundant and best known. In fact, the record of mammal evolution in South America is so complete that these fossils are used by geologists and paleontologists to subdivide geologic time. The occurrence of unique associations of taxa that are inferred to have existed during a restricted interval of time has resulted in the recognition of discrete chronostratigraphic units called Land Mammal Ages. These ages were established on the basis of knowledge of stage of evolution of the taxa, on their time of first and/or last appearahce in the fossil record, and on changing faunal associations through time. The sequence of South American Land Mammal Ages (SALMA) has been based largely on knowledge of the exceptionally rich and complete record in Argentina (Marshall, 1985). Detailed systematic studies of taxa along with geochronologic studies and magnetostratigraphy of the fossiliferous rock sequence and/or radioisotopic (Ar/Ar, K-Ar) dating of associated volcanic rock units (i.e. basalts, tuffs, ignimbrites) permit geologists and paleontologists to correlate Bolivian mammal faunas with the Argentine sequence atid to make distinctions between ecological and temporal relationships of local faunas and faunal assemblages. The result of such studies is that land mammals have proven very useful for dating and correlating rock units within Bolivia in particular and with other South American countries in general.

We provide a review of the Eocene to Pleistocene land mammal record of Bolivia within its stratigraphic and tectonic context. The use and chronology of South American Land Mammal Ages follows Marshall (1985) as supplemented by Marshall, Drake e¿ al. (1986), and Marshall, Cifelli ef al. (1986). Recently, Tonni et al. (1987) recognized a new ,Pleistocene Land.Mamma1 Age between the Ensenadan and Lujanian which they called Centinelan. However, the validity and utility of this new age has yet to be f m l y established in Argentina, and unti this is done it is futile to attempt to recognize it in Bolivia. In addition, Marshall & Salinas (1990) have shown that

the type fauna of the Friasiali Land Mammal Age (conventionally middle Miocene) in southern Chile is temporally equivalent to the Santacrucian Land Mammal Age. They thus use Colloncuran for the land mammal age between Santacrucian and Chasicoan. For all practical purposes, Friasian of previous workers is equivalent to Colloncuran as used in this study.

This paper represents an expansion and updating of the Bolivian land mammal record as provided by Robert Hoffstetter (in Marshall el al. 1983, 1984). As documented below, the highlights of this record include: the taxonomically richest and best studied faunas of late Oligocene-early Miocene (Deseadan) and early Pleistocene (Ensenadan) age in all o[ South America; and the exceptionally rich record of late Miocene (Huayquerian) and early to middle Pliocene (Montehemosan) age faunas from the northern Altiplano.

The Altiplano, including the Puna in adjacent Argentina and Chile, is a high-altitude plateau which covers southwest Bolivia, southeast Peru, northeast Chile and northwest Argentina. It is about 200 km wide and about 1500 km long, and some 300,000 km2 at 3,600- 4,000 m (mean 3650 m; Isacks, 1988) of altitude. In Bolivia, the Altiplano covers about 170,000 km2 and is situated between the Cordillera Occidental and Cordillera Oriental.

The following abbreviations are used: GEOBOL, Servicio Geológico de Bolivia; ka, thousands of years ago, a point in time; kg, kilograms; km, kilometers; m, meters; Ma, megaannum or millions of years ago, a point in time; M y , millions of years, a duration of time; yrbp, years before present.

GEOLOGICAL EVOLUTION OF BOLIVIA: EOCENE TO PLEISTOCENE

The reader must first be aware that the geologic evolution of the central Andes is currently being re-evaluated, and that traditional models are being challenged. The latter envision that the central Andes were subjected during most of Cenozoic time to a tectonic regime characterized by long tensional periods (during which the sedimentary basins formed), short synchronous compressional pulses, and generally high-angle faulting (Mégard, 1978; Dalmayrac el al., 1980; Martinez, 1980; Lavenu & Marocco, 1984; Mégard et

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LARRY G . MARSHALL & THIERRY SEMPERE

al. 1984; Lavenu, 1986; Sébrier et al., 1988). In contrast, new data and new interpretations favor structural models dominated by progressive crustal shortening, thrust propagation, and foreland basin evolution (Jordan et al., 1983; Jordan & Alonso, 1987; Isacks, 1988; Roeder, 1988; Sempere et al., 1988, 1989, 1990a, b; Baby et al., 1990; Sheffels, 1990).

In Bolivia, the two models of Andean tectonics are sometimes at odds with each other. For instance, the thick Cenozoic clastic strata of the Altiplano were traditionally thought to have been deposited during long epochs of extension with short interruptions by compressive pulses. It is now believed that their deposition took place mostly in intermontane foreland basins (i.e. in permanently compressional settings; Baby et al., 1990; Sempere et al., 1990a, b, 1991). Predominance of compressive conditions in the central Andean area since late Cretaceous time was first suggested i n a general way by Marocco ef al. (1987).

The angular unconformities observed on the Altiplano and elsewhere in the Bolivian Andes have traditionally been interpreted as materializing the mentioned "compressional pulses". However, this is not the only possible interpretation for these angular unconformities (Sempere, 1991). Moreover, although details of some important field observations relative to deformations in the Altiplano have been well described, in particular in the works of Martinez (1980), Lavenu (1986) and Lavenu et al. (1989), several independent new chronologidal data make untenable the traditional timing of deformation (Sempere et al., 1990b).

Therefore, the Calidity of the six "compressional tectonic pulses" or "phases", as listed by Sébrier et al. (1988), may be questioned. Intuitively, it seems unlikely that the enormous central Andes, which today are second only to the Himalayas in size and height of the mountain belt, crustal thickness, etc., developed by a small number of short "compressional pulses".

In this paper we adopt the tectonic model and stratigraphy currently being worked-out by the Orstom-YPFB research program on the geology of Bolivia (Sempere et al., 1989, 1990a, b, c; Sempere, 1990), which we summarize below. A map showing the tectonostratigraphic domains presently recognized i n Bolivia (Sempere ef al., 1988, 1990a). and the location of the main sedimentary basins of late Oligocene-Pleistocene age are shown in Figure 1.

The geological history of Bolivia since the Eocene consists of two tectosediinentary periods, respectively spanning the Eocene-early Oligocene and late Oligocene-Present intervals (Sempere et al., 1989, 1990a; Sempere, 1990).

During the Eocene-early Oligocene time span, the paleo-Andes were located west of the Bolivian territory, and their associated continental external foreland bash , resembling the present-day Chaco plain, occupied what is today tlie Altiplano and most of tlie Cordillera Oriental. At - 27 Ma, a major tectonic crisis began to develop, in conjunction with important changes in plate convergence velocity (Pardo-Casas & Molnar, 1987), and lasted until - 19 Ma (Sempere et al., 1990b, c). An important phase of magmatic activity developed during the same interval. It must be stressed that the Bolivian Andes started to exist as a mountain belt, albeit of limited altitude, only at that time. Concurrently, the Andean external foreland basin rapidly shifled eastwards, reaching the Subandean- Llanura domain, while several intermontane basins formed in the Andean domain, including the large ones on the Altiplano.

After a time of relative quiescence (- 19-17 Ma), magmatism slowly resumed a t - 17 Ma (Grant et al., 1979; Redwood & MacIntyre, 1989) and tectonism at - 14 M a (Sempere, 1990). and considerably increased at 11-10 M a with the onset of the second major tectonic crisis (Sempere et al., 1989). This crisis lasted until - 5 Ma (Sempere et al., 199Oa), but tectonic and magmatic activities have lingered on to the present. There is apparently little relation between the onset of this second tectonic cr is is and plate convergence history.

Each tectonic crisis was followed by the development of an extensive planation surface, respectively the Chayanta surface in the middle Miocene and the San Juan del Oro surface during the late Miocene-early Pleistocene interval (Servant et al., 1989; Sempere et al., 199Od).

STRATIGRAPHIC FRAMEWORK

The Cenozoic stratigraphy of Bolivia strongly relies on knowledge of the basins where the strata were deposited. As already mentioned, the Eocene-early Oligocene area of sedimentation was a large foreland basin, and its paleo-landscape was a wide alluvial plain that probably resembled the present-day Chaco-Beni lowlands. In contrast, the late Oligocene-Pleistocene period was characterized by numerous separate intermontane basins, many of small size, that developed in deformed areas, and by the large Subandean-Llanura external fxeland basin of the Chaco-Beni lowlands.

The lower boundary of the Eocene-early Oligocene period coincides with the upper boundary of the Kimmeridgian-Paleocene Puca Group (Sempere el al., 1988; Jaillard & Sempere, 1989; Sempere, 1990). This locally angular unconformity (Marocco et al., 1987) marks the initiation of the foreland basin which developed, in what is today the Bolivian Altiplano and.Cordillera Oriental, during Eocene-early Oligocene time (see above), and very likely resulted from a deep modification of the geodynamics of the Andean margin at that time. Although approximately located at the Paleocene- Eocene boundary (Cirbián et al., 1986; i.e.- 53 Ma according to Cowie & Bassett, 1989, and Odin, 1989; Fig. 2), this tectonic change might be related to the plate rearrangement which occurred in the Pacific area at anomaly 24N (Lonsdale, 1988), i.e. in the late early Ypresian (ßerggren et al., 1985; Cavelier & Pomerol, 1986; Haq ef af., 1987) at - 5 1-50 Ma (according to updated information in Cowie & Bassett, 1989, and Odin, 1989). Such an age for this major change in Andean geodynamic conditions nearly coincides with the 50-49 Ma age for termination of emplacement of the coastal batholith of Peru (Soler, 1987), which also reflects a niajor change in modalities of subduction.

27 Ma (Sempere ef al., 1990b) which coincides with the early Oligocene-late Oligocene boundary of Cowie & Bassett (1989). The tectonic upheaval which started a't ttiat time resulted in development of numerous small to mediuni-size basins in the area of the Altiplano and, especially, Cordillera Oriental.

Within the Andean domain during both major tectonic crises, thrust deformations developed more particularly in certain areas and along specific structures, and intermontane foreland basins formed in relation to them. Examples are the northern Altiplano basin, foreland of the Huarina fold-thrust belt and Coniri thrust system; the Río Mulatos basin, foreland of Uie Sevaruyo-Chita fold-thrust belt; the

The boundary between these two tectosedimentary periods is

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FOSILES Y FACIES DE BOLMA - VOL. I VERTEBRADOS , .

Rolívar-MondragBn basin, foreland of lhe Main Altiplanic thrust; the Lípez basin, foreland of the Khenayani fault system; etc. ... (Fig. 1).

Other small basins can be considered as piggyback basins, completely or nearly isolated from others due to reliefs developed by thrusting. Examples are the basins of Salla-Luribay, Lacayani, Tarabuco, probably Muyu Huasi, Tipuani (Fornari et al., 1987), Padilla, Tarija and San Isidro. The San Juan del Oro planation surface and its related deposits originated by the action of a longitudinal fluviatile system trapped within the Cordillera Oriental (Sempere et al . , 1990d), which can be considered as a giant piggyback basin.

Other basins formed in relation to wrench-faults. Examples are the Tupiza and Río Khuchu basins, and the basin system of the Cochabamba "valles".

Present knowledge of the Eocene-Pleistocene chronostratigraphy of Bolivia, including some unpublished data, has been summarized by Sempere & Oller (1987) and Sempere (1990), and is shown in Figures 2 and 3. Partly due to the numerous basins or sub-basins, multiplication of formational names during the 1960's has unnecessarily complicated the stratigraphic nomenclature. Many names of local value have therefore been eliminated from our stratigraphic charts. Some of these are mentioned in the text when used in the cited literature, and their preferred equivalent is given.

Of the two tectosedimentary periods defined above, the second one, which spans the late Oligocene-Pleistocene interval is by far the richest in fossil vertebrates, as documented below.

VERTEBRATE FAUNAS AND LOCALITIES

EOCENE (Casamayoran-Mustersan)

A probable Casamayoran age fauna reported by Sig6 et al. (1984) includes remains of actinopterygian fish (Characiformes, Serrasalmidae, Myleinae; Siluriformes), indeterminate turtles (Broin, 1991), crocodile teeth, and a single upper premolar of a primitive notoungulate mammal close to Camargomendesia (sensu Cifelli, 1983) from a locality they designated Vela Pachita, about 57 km southeast of Challapata, in what they considered to be the Santa Lucía Formation. However, the correct name of this locality is Wila Apacheta and the fossils are from the basal Cayara Formation which rests unconformably on the El Moliio and/or Santa Lucía formations (Marocco et al., 1987); the age of this unconformity shouldsbe 53 or 51-50 Ma (see above).

Also from the Cayara Formation at La Cabaña on the Cochabamba-Oruro road, about 25 km southwest of Cochabamba, were recovered remains of fish and reptiles (crocodiles, turtles) from just below a level with abundant plants; turtles were observed in the upper levels of the Cayara Formation at Tiupampa, about 95 km southeast of Cochabamba; and indeterminate fish and turtles wcre recovered Iiom Ulis formation about 5 kin north-northeast of Chita.

A dubious record of a Casamayoran age locality was given in an unpublished report by E. Ortega in 1968. This report was seen by Hoffstetter in GEOBOL, La Paz, although attempts to relocate it by one of us (L.G.M.) in 1989 were unsuccessful. According to Hoffstetter (in Marshall et al., 1983, p. 41), Ortega recorded remains of mammals, including a fragment of a jaw of a Notoungulata (Interatheriidae, Nofòpithecus sp.), from the "areniscas rojas del

Anticlinal de San Andr6s" (=San Andres Formation of Evemden el al., 1966 which has a dubious associated K-Ar age of 38 Ma on "glauconite") to the west of San Andres de Machaca on the Altiplano just south of Lago Titicaca. The fossils reputedly came from a unit equivalent to a part of the Mauri Formation (s.[.; YF'FB, unpublished data) and is thus late Oligocene-Miocene in age (Lavenu et al., 1989), though Eocene age sediments have been traditionally mapped in this area based on the one age obtained on "glauconite" (Martinez, 1980). Glauconite is widely considered to be a marine mineral, whereas only continental strata have been deposited in the Altiplano since the Paleocene. Hence, the age determination by Evemden et al. is dubious because the dated clay mineral is probably not authigenic. Unfortunately, these fossils were never described, Ortega (1970) made no mention of their existence in his review of Bolivian fossil faunas, and they cannot be located in the GEOBOL collections.

LATE OLIGOCENE-EARLY MIOCENE (Deseadan)

The most spectacular land mammal fauna of Deseadan age in all of South America is from the Salla-Luribay basin, about 95 km southeast of La Paz in the Cordillera Oriental (Hoffstetter, 1968b). The principal fossil-bearing unit lias been called the Estratos de Salla (Evemden et al., 1966, 1977; Villarroel & Marshall, 1982). Strates o u Couches de Salla (Hoffstetter, 1976a) and Salla Beds (MacFadden et al., 1985) which consist of - 540 m of well-indurated red-brown, pink-tan and'whitish claystones and siltstones deposited primarily in a fluviatile environment. The Estratos de Salla represent a unit partly equivalent to the Coniri Formation (Hoffstetter, 1968b; Sempere et al., 1990b).

The geology and fossil localities are discussed by Hoffstetter (1968b, 1976a), Villarroel & Marshall (1982) and MacFadden et al. (1985). The latter provide a magnetostratigraphic and radioisotopic study of the Salla Beds and conclude that they span a time interval from about 28.5 - 24.0 Ma, making this the best dated rock unit of Cenozoic age in Bolivia. MacFadden et al. (1985) also demonstrate that the fission-track dates of 54.0 k 2.6 and 52.0 It 2.1 Ma rehrted by Hayashida et al. (1984) for the Salla Beds are too old and apparently represent dates obtained on detrital (reworked) zircon grains. Naeser et al. (1987) published three fission-track (34.5 f 4.0, 24.2 f 3.6, 23.5 f 2.2 Ma) and four K-Ar (biotite- 28.0 f 0.9, 27.2 rt 0.9, 27.9 f 0.9, 25.1 f 0.7 Ma) dates from four ash levels in the lower part of the Salla Beds and conclude that the principal fossil horizons range from 27-24 Ma, while the complete section ranges from about 28-22 Ma. These dates are consistent with those of Hayashida & Danhara (1985) who report four fission-track dates (27.2f1.6,25.0k1.5,26.1f 1.9,24.0flSMa)onzirconsf?oman unspecified level(s) in the Salla Beds. The geochronology of the Salla Beds is summarized by MacFadden (1990b) and McRae (1990). Sempere ef al. (1990b) reinterpret the geochronologic data presented by MacFadden et al. (1985) and suggest that their dated section may be 3.0-4.5 Myr younger.

The diverse mammal fauna includes: Marsupialia (Borhyaenidae, Notogale mitis, Paraborhyaena boliviana, Pharsophorus lacerans, Sallacyon hoffsletteri: Caenolestidae, Palaeothentes boliviensis; ?Polydolopidae or Palaeothentinae. gen. et sp. indet.; Argyrolagidae, Proargyrolagus bolivianus), Edentata (Dasypodidae, gen. et sp. indet.; Peltephilidae, cf. Peltiphilus sp.; Glyptodontidae, cf.

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(*' noulhsm SJO Surfoca \, / of Subandaon \/ dsformdtlon L- 'i. 69' i. A , R G 65E N T I $3' I I

Figure 1. Sketch-map of principal late Oligocene-Pleistocene age sedimentary basins and tectonostratigrapllic boundary faults in Bolivia. Abbreviations for time: O, Oligocene; M, Miocene; P, Pliocene; PI, Pleistocene; H, Holocene; e, early; m, middle; 1, late. Abbreviations for fhults and surfaces: CALP, Cabalgamiento Altiplsnico Principal (Main Altiplanic Thrust); CANP, Cabalgamiento Andinò Principal (Main Andean Thrust); CCR, Cabalgamiento de la Cordillera Real (Cordillera Real Thrust); CFP, Cabalgamiento Frontal Principal (Main Frontal Thrust); FAT, Palla Aiquile-Tupiza (Aiquile-Tupiza Fault); FC, Falla Cochabamba (Cochabamba

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Glyptatelus sp.; family indet., Pseitdoglyptodon sallaensis; Megalonychidae. II. gen. e t n . sp; Mylodontidae, cf. Ocfodonfotheriiint sp.), Condylarthra (Didolodontidae. Salladolodlts deuterotheroides), Primates (Cebidae, Branisella boliviana), caviomorph Rodclilia (Octodontidae, Migraveranius beatus; Echimy idac, Sallaniys pascitali; Dasyproctidac, Incaniys bolivianus, cf. Neoreoniys sp. , Cephaloniys bolivianus; Dinomyidae, Branisamys luribayensis), Litopterna (Macraucheniidae, ?Coniopternium printitivunz; Adianthidae, Tliadanius Itoffstetteri, Tricoelodus boliviensis), Notoungulata (Isotemnidae, gen. et sp. indet.; Notohippidae, ?Rltynchippus cf. eqiiinirs, ?R. cf. puntidis; Toxodontidae, Nesodontinae, gen. et sp. indet.; Hegetotheriidae, Prohegetotlieriunt sp.; Arcliaeohyracidae, Archaeohyrax sp.; Interatlieriidae, Argyroltyrax sp.; Mesotheriidae, Tracltytkerus sp.), Astrapotheria (Astrapotheriidae, gen. et sp. indet.), Pyrotheria (Pyrotheriidae, Pyrotheriuni ronieri). order and family incertae sedis (cf. Acanta sp.) (Cifelli & Soria, 1983a, b; Engelmann, 1987; Hartenberger, 1975; Hoffstetter, 1968b, 1969, 1976a; Hoffstetter & Lavocat, 1970; Hoffstetter & Petter, 1983; Lavocat, 1976; MacFadden et al., 1985; MacFadden & Frailey, 1984; Patterson & Marshall, 1978; Patterson & Wood, 1982; Petter & Hoffstetter, 1983; Soria & Hoffstetter, 1983; Villarroel & Marshall, 1982; Wolff, 1984, 1985). Of noteworthy importance is Branisella boliviana, the oldest primate known i n South America (Hoffstetter, 1969; Rosenberger, 1981; Wolff, 1985). Turtles (Chelonia, Podocnemididae, ?Podocnemis sp.) are also recorded (Broin, 1991).

A second Deseadan fauna is from Lacayani, located about 30 km southeast of La Paz (Hoffstetter ef al., 1971). The fossilsi which come from a n unnamed rock u n i t include: Marsupialia (Rorhyaenidae), Edentata (Dasypodidae, cf. Prozaedyus; Glyplodontidac, Glypfnfe lus; Orophodonlidae), Litopterna (M acr a u ch en i id ac , No to u II g u 1 a t a (Mesotheriidae, 7rachytherus spegazzinianus; Hegetotheriidae, Prohegetoherirmi), and caviomorph Rodentia (Cephaloinyidae, gen. et sp. indet.; Chinchillidae, Eoviscaccia boliviana) (Hoffstetter et al., 1971; Hartenberger, 1975; Vucetich, 1988, 1989).

A poorly known fauna from the base of the Petaca Formation at Quebrada Saguayo in the Subandean belt, about 60 km west- northwest of Santa Cruz, is probably of Deseadan age. The known fauna includes a right maxilla of a mammal identified as ?Rhynchippus sp. (Notoungulata, Notohippidae, Rhynchippinae) by Villarroel (in Sanjinés & Jitn-énez, 1975; see also Hoffstetter, 1977, p. 1519), a small plate of an indeterminate armadillo (Dasypodidae) and remains of a tortoise (Chelonia, Testudinidae, cf. Cltelonoidis

c f . Con iopt ern iuni) ,

sp.; Broin, 1991). This age assignment is based on the presence of Rltyncltippus, a genus known only from Deseadan faunas elsewhere in South America (Marshall, Cifelli el al., 1986). In addition, the subfhily Rhynchippinae is unknown after Deseadan time, at least in Argentina.

III the Corocoro area, a cast of a single footprint of a large edentate was collected from what was called the Desaguadero Series, in a small quarry along the railroad about 3 km southwest of Corocoro from rocks which belong to the middle part of the Coniri Formation (Cherroni & Cirbiln, 1970). This footprint is figured by Singewald & Berry (1922, pl. 6, p. 52), but its true identity has yet to be established. Because of its stratigraphic position, this edentate foot print may be of late Deseadan age.

Lastly, geologists of the Gulf Oil Corporation collected a partial fossil turtle from along the Rio Cesarsama at a locality they called Icharco, about 30 km south of Todos Santos and 115 km northeast of Cochabamba. The fossil was sent to Dr. Donald Baird of Princeton University who believed that it was of Tertiary age. This fossil probably came from what López (1983, p. 21) either calls the Bala Formation which is equivalent to the Petaca Formation or froin what he calls (p. 24) the Quendeque Formation, of probable late Miocene age (Fig. 2). Correspondance on the discovery and identification of this fossil is in the archives of the Museo Nacional de Historia Natural, Cochabamba (letter from T. A. Kibby to D. Baird, May 10, 1961).

EARLY AND MIDDLE MIOCENE (Colhuehuapian-Chasicoan)

A relatively rich fauna of middle Miocene age is known from an unnamed unit at Quebrada Honda (3500 m), about 55 km southwest of Tarija, just north of the Argentine border in southernmost Bolivia. This unit is of fluvio-lacustrine origin and is only slightly deformed. The fauna was assigned a Colloncuran (Friasian) age by Hoffstetter (1977), and subsequent study by Frailey (1988) suggested that it was Santacrucian. However, recent geochronologic work by MacFadden (1990a) and MacFadden et al . (1990) shows that most of the Quebrada Honda strata were deposited between 13 and 12 Ma, indicating that the fauna is late Colloncuran in age. A brief description of the geology is given by MacFadden & Wolff (1981). The fauna includes: Marsupialia (Borhyaenidae; Caenolestidae; Argyrolagidae, Ifondalagus altiplanensis), Edentata (Dasypodidae; Glyptodontidae, Propalaeohoplopltorus andinus; Mylodontidae; Megalonychidae, Napalops angustipalafus), Notoungulata

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Fault); FCA, Falla Chita-Arica (Chita-Arica Fault); FCC, Frente de Cabalgamiento Coniri (Coniri Thrust Front); FE, Falla Eucaliptus (Eucaliptus Fault); FSI, Falla Sevaruyo-Incapuquio (Sevaruyo-Incapuquio Fault); SFK, Sistema de la Falla Khenayani (Khenayani Fault System); SJO, San Juan del Oro planation surface. Basins and ages: 1, Beni basin (M-H) and adjacent northern Subandean basin (IO-P); 2, Chaco basin (M-H) and adjacent southern Suhandean basin (10-P); 3, Chiquitano basin (?-H); 4, Tipuani basin (IM-P); 5, San Isidro basin (IP-ePI); 6, Muyu Huasi basin (1M); 7, Padllla basin (P-PI); 8, Tarija basin (PI); 9, Tarabuco basin (?-?); 10, Culpina basin (?-H); 11, Quebrada Honda basin (mM); 12, San Juan del Oro surface related deposits (IM-PI); 13, Cochabamba basin system, including Anzaldo and Sacaba basins (IM-Pl); 14, La Paz basin (P-PI); 15, Ulla-Ulla basin (?-Pl); 16, Lacayani basin (10-eM); 17, Salla-Luribay basin (IO-eM); 18, Northern Altiplano basin (10-H); 19, noIlvar basin (IO-eM); 20, Mondragh I)asin (10-eM); 21, Rfo Mulatas basin (M); 22, Llpez basin (IO-H); 23, Rfo Khuchu basin (10-M); 24, Tupiza basin (10-M); 25, Uyuni basin (10-H); 26, Salinas de Gard Mendoza basin (?-H); 27, Carangas basin (M-H); 28, Charaña basin (M-H). The Andean domain lies wesf of the CANP, whereas the Subandean belt (S.S.) extends between the CFP and the present-day edge of deformation to the east.

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( s / d 'unnamed

Figure 2. Clironostratigrapliic chart sliowing Eocene-middle Pliocene (Casamayoran-Chapadmalalan) South American Land Mammal Ages (modified after Marshall, 1985) and principal vertebrate-bearing formations (*) discussed in text (modified after

Sempere, 1990). Geologic time scale follows Berggren et al. (1985)

(Hegetotheriidae, Hegefofheriuni sp.; In teratheriidae; Mesotheriidae; Toxodontidae), Astrapotheria (Astrapotlieriidae, ?Xenasrr~~otheririni sp.), Litopterna (Proterotheriidae, Diadiaphorus sp.; Macraucheniidae), and caviomorph Rodentia (Octodontidae; Echiniyidae; Capromyidae; Chinchillidae, Prolagosloniiis sp.; Caviidae) (Hoffstetter, 1977; MacFadden & Wolff, 1981; Takai et al., 1984; Frailey, 1987, 1988; Villarroel & Marshall, 1988).

The 300 m-thick Quebrada Honda strata accumulated by infilling of tlie Pasajes syncline which formed just west of the CANP major fault (Fig. 1). This syncline is bounded on its western side by a skinger of en-échelon anticlines which involve Cambrian and early Ordovician strata and document a regional right-lateral component for the CANP (Sempere, unpublished). The formation of the Pasajes syncline is thus likely to have been coeval with the first major tectonic crisis mentioned above (27-19 Ma). After deformation had ceased, differential erosion of Ordovician shales and Cambrian quartzites, and probable local faulting; led to formation of a hollow depression in the central part of the Pasajes syncline were fluvial and lacustrine sediments. as described by MacFadden & Wolff (1981), gently accumulated. These deposits are thus partly coeval with the development of the middle Miocene Chayanta planation surface (Sempere et al,, 1990e). and with the deposition bf the Quehua Form ation.

A second relatively rich fauna of Colloncuran age is reported by Ois0 (1991) from the middle and lower members of the Nazareno Formation about 10 km south of Nazareno (on the west side of Estación Arenales; 21"40'S, GS"3S'W) and 30 kin southeast of Tupiza in the Cordillera Oriental, department of Potosí, in the Tupiza basin of southern Bolivia. Here the Nazareno Formation consists

636

mainly of conglomerates, reddish-brown siltstones and mudstones, and volcanic ash. These sediments are poorly indurated and reach a maximum thickness of - 160 in. The reported fauna includes 10 taxa referable to S orders and 8 families: Marsupialia (Borhyaenidae, Acrocyon?), Edentata (Dasypodidae, Stemtatus sp., cf. Pelfej~hiliis sp.; Glyptodontidae, Propalaelioplophorics sp., Neothoracoplioriis? sp.), Notoungulata (Mesotheriidae, Plesiotypollzeriuni sp.; Hegetotheriidae, lfegetofheriuni sp.), Litopterna (Proterotheriidae, Diadiapliorus sp.), and Rodentia (Octodontidae, gen. et sp. indet; Chinchillidae. Prolagosfonws sp.).

Also from the Nazareno Formation at Suipacha, 3 km north- northwest of Nazareno, an armadillo was collected during construction of a railway cut at km 69 on the line from Villazón to Atocha. This specimen was described by Castellanos (1925) and named Dasypodon afavus (Edentata, Dasypodidae, Euphractinae). Hoffstetter (1977) tentatively regarded this fossil as Huayquerian. Ois0 (1991) regards Dasypodon alnvris as a small species of Slenotafus (i.e. S. afnvus), and given its provenance from the Nizareno Formation is also almost certainly of Colloncuran age (sensu Marshall & Salinas, 1990).

Huxley (1860; see also Blakk, 1861) described the partial skeleton of a litoptern (Macratcchenia boliviensis) from what Singewald & Berry (1922, p. 44) call the Ramos Series at Corocoro. a copper mine on the Altiplano south of La Paz. This unit is equivalent to the Kollukollu Formation (Cherroni, 1974) which has a K-Ar date of 16.6 f 0.4 Ma on a sanidine concentrate from a reworked tuff (Swanson el al., 1987). Hoffstetter & Paskoff (1966, p. 483) cotifinn that this specimen is indeed a macraucheniid. but note that it is not referable to the Pleistocene genus Macrarcclienia and is smaller than

FOSILES Y FACES DE BOLIVIA - VOL. I VERTEBRADOS

thc carly to middle Miocene gcnus Tlieosodon. Furthermore, the specimen is poorly prescrvcd and a secure generic identification appears improbable (Ahlfeld & ßranisa, 1960, p. 165). Thus, the true gencric idcntity and age of this species remains unknown. Because of its stratigraphic position, this macraucheniid might be of Colhuehuapian or Santacrucian age.

There are two poorly known faunas of possible Colloncuran age in Bolivia. The first is from the Choquecota Formation (=Caquiaviri Formation, which near its base contains blocks of dacite lava K-Ar dated at 14.2 f 0.4 Ma; Swanson et al., 1987) about 3 km north of Choquecota, department of Oruro, on the Altiplano (see Hoffstetter et al., 1972). This was the site of collection of a small notoungulate (Mesotheriidae) which Villarroel (1974b) named Microfypofheriuni choquecoteme. Remains of Dasypodidae (Prozaedyus), Glyptodontidae, Hegetotheriidae and Chinchillidae are also known (Hoffstetter el al., 1972). The second locality is in southwestern Bolivia between Cerdas and Atocha, where Microtypolherirmz cf. M. choquecoteme was collected from tlie lower part of the Quehua Formation S.S. (mapped as "Formación Quehua Superior'' on Hoja 6331, Quechisla) (see Hoffstetter, 1977; Villarroel, 1978, p. 166; Hoffstetter in Marshall et al., 1983, p. 41).

A small species of Notoungulata (Mesotheriidae, Plesiofypofheriuni niinus Villarroel, 1978) was collected 3 kin southeast of Cerdas from the upper part of the Quehua Formation S.S. (mapped as "Formación Quehua Superior" on Hoja 6331, Quechisla). This species appears to be more specialized than Microfyyotheriuni choquecoteme suggesting that it may be Chasicoan in age, although this has yet to be demonstrated (Villarroel, 1978; Hoffstetter in Marshall et al., 1983, p. 41).

A locality from the uppermost part of the Petaca Formation on the Río Yapacani, about 90 kin west-northwest of Santa Cruz in the Subandean belt yielded a single right mandible with five teeth which was identified by Pascual and Odreman Rivas (in Sanjinés 6c Jiménez, 1976) as cf. Vassallia minuta (Edentata, Dasypodidae, Pampatheriinae). This identification indicates a Chasicoan to Montehermosan age for this level of the Petaca Formation.

A few vertebrate fossils have been recovered from the Yecua Forination, which overlies the Petaca Formation, along the Río Alto Moile, about 95 km west-northwest of Santa Cruz in southcentral Bolivia (López, 1983, p. 18). The known fauna includes a limb bone o f a litoptern tentatively identified as cf. Theosodon sp. (Macraucheniidae), an indeterminate rodent tooth, the first fossil remains of the fish order Gyninotiformes (Apteronotidae, gen. et sp. indet.) (electric eels) (Gayet, 1986) and indeterminate Siluriformes (Gayet, 1991). If the identification of Tlieosodon is correct, then the age of this fauna is somewhere between Colhuehuapian and Chasicoan, which is the known stmtigraphic range of this genus elsewhere in South America.

The occ,urrence of the Chasicoan to Montehermosan cf. Vassallia niinula below a level with the Colhuehuapian to Chasicoan cf . Theosodon sp. implies that the top of the Petaca Formation and at least a part of the Yecua Formation are Chasicoan in age (Fig. 2). This age assignment is supported by the fact that the Yecua Formation represents the northern extent of the Paranense epicontinental sea which is, at least in part, temporally equivalent to Chasicoan (Sempere, 1990). The fish fossils reported by Lbpcz (1975) from tlie base of the Tariquía Formation along the

Alto Rio Moi l e a r e appa ren t ly a l s o of Cllasiconri or Huayquerian age.

A fauna of probable Chasicoan age is reported by Russo (1959, p. 29) from "un afluente derecho, sin nombre, de la Quebrada de Palmar" at Agua Salada near Yacuiba in southeast Bolivia just north of the Argentine border. The fossils were found in sediments which Russo called the "Chaco Inferior" and are now called the Tariquía Formation, which overlies the Yecua Formation. As noted by Russo (p. 29), "en una arenisca situada directamente sobre el banco tobaceo gris, se hallaron huesos, dientes y un bozo de columna vertebral de unos 40 centímetros de longitud, con apófisis dorsales y costillas aún sujetas a él, de un mamífero fósil de hábito terrestre. Estos fósiles no han podido ser determinados en el campo, su clasificación requeriría el trabajo de un especialista y a h a s í sería difícil hacerlo debido a la pobreza del material recolectado".

From the base of t he Guandacay Forma t ion a few kilometers north of Bermejo along the Rio Bermejo, Ing. Antonio Sadud collected a partial skull and skeleton of a notoungulate (Hegetotlieriidae; determined by R. Pascual). This formation is apparently Chasicoan to Huayquerian in age.

LATE MIOCENE (Huayquerian)

There are numerous land mammal faunas of Huayquerian age in Bolivia, particularly from the Mauri 6, Rosa Pata and Quehua formations on the Altiplano. At localities where these formations were deformed during Huayqueriaii time they are disconformably overlain by rocks of Pliocene and/or Pleistocene age. These deformations on the Altiplano correspond to the second major tectonic crisis mentioned above (11-5 Ma), and apparently to what is termed the Quechua deformation in Argentina (Hoffstetter, 1986, p. 222) which began about 10 +_ 2 Ma (Jordan & Alonso, 1987).

A sample which yielded a K-Ar age of 10.5 Ma (Evernden ef al., 1966, 1977) was apparently collected from a tuff about 1500 m above the base of the Mauri 6 Formation at Cerro Jakokota (=Hakakota) (4,000 m), 12 kni southeast of Santiago de Machaca. This locality may be the same as Cerro Jancocota where Berry (1922) collected and described a fossil flora that includes leaves of Pteris, Pliragmites, Alnus, Osteomeles, Polylepis, Calliandra, Cassia, Cesalpinia and Melastoniites; fossil wood of Prosopis (Mimosaceae) occurs below the tuff at this locality (Hoffstetter, 1986). The Mauri 6 is disconformably overlain by the subhorizontal Pérez Ignimbrite which has a mean radioisotopic age of - 2.8 Ma (Evernden et al., 1966, 1977; Lavenu et al., 1989; Marshall er al., 1992) and probably belongs to the same igiiimbritic flow as the Chijini and Ayo Ayo tuffs which are also - 2.8 Ma (Marshall el al., 1992).

The richest of the mammal-bearing Mauri 6 localities is at Acliiri (especially at Cerro Pirapi Grande, about 6 km from Achiri) which occurs in the upper part of this formation. Ofier noteworthy Mauri 6 localities include Canacho, Jankojakhe (=Jankoaqui) and Rosario. The known fauna from these four localities includes: Marsupialia (ßorhyaenidae, Borliyaenidirim altiplanicus), Edentata (Dasypodidae, Chorobates sp., cf. Kraglievìchia sp.; Glyptodontidae, Sclerocalyptinae; Megalonychidae; Mylodontidae), and Notoungulata (Toxodontidae, Toxodontinae, gen. et sp. indet., and a new form with a frontal horn, see Hoffstetter, 1976b, pp. 124-

'

637

LARRY G.'hURSIIALL 8r'I'IUERRY SEMPERE

125 for photo: Mesotheriidae, Plesiotypotlieriunt aclrirense, P. niajus) (Villarroel, 1974a; Villarroel & Marshall, 1983; Hoffstetter, 1986).

Douglas (1914, p. 24) collected a fragment of the symphysis-of a notoungulate (Toxodontidae) from "a few miles below the Mauri bridge" from what he called the Desaguadero Formation along the Rio Mauri, a tributary of the Rio Desaguadero. Villarroel (1977, p. 29) notes that the Desaguadero Formation of previous workers has no significance and it is not possible to securely know what stratigraphic units ih current use were assigned to it. Nevertheless, Ahlfeld & Branisa (1960, p. 134) believe that the specimen collected by Douglas came from the upper part of the Mauri Formation, and is probably from the Mauri 6. This specimen was identified by C. W. Andrews of the British Museum (Natural History), London as Nesodon sp., a genus known securely only from rocks of Santacrucian and Colloncuran age in Argentina (Marshall et al., 1983). Simpson (1940) reported that this specimen is no longer in the collections of the British Museum and as such its identity cannot be confirmed. For the present this taxon can only be regarded as Toxodontidae, gen. et sp. indet.

Land mammals have been collected from the upper part of the Totora Group, 2 km north of Ulloma at Minita Chocopini near Torini, 4 km west of Callapa, north of Chacarilla, and in the vicinity of Curahuara de Carangas (Hoffstetter, 1986). Two tuffs from the Rosa Pata Formation (upper part of the Totora Group) named toba Callapa and toba Ulloma, have been K-Ar dated at about 9.0 and 10.4 Ma, respectively (Marshall et al., 1992). The Rosa Pata Formation is either disconformably overlain by the latest Miocene Pomata Formation, Pliocene Umala Formation which has a mean radioisotopic date of 5.4 Ma for its basal tuff (=toba 76, toba Umala or toba Jankhomarka; Thouveny & Servant, 1989; Marshall et al., 1992), Pérez Ignimbrite dated at 2.8 Ma (see above), or Pleistocene Ulloma Formation (see below; Marshall et al., 1983; Hoffstetter, 1986). The known mammals include: Edentata (Dasypodidae, Pampatheriinae; Glyptodontidae), Litopterna (Macraucheniidae?) and Notoungulata (Mesotheriidae, P seudofypotlierirrni sp.) (Martinez & Rosales, 1972; Hoffstetter et al., 1972).

From the base of a 205 m section of what are informally called the Micaiía beds at Micaiía in the Cordillera Oriental (17'30's. 67"24'W; 38004000 in) were recovered a niediuni-sized niegatheriid ground sloth (gen. et sp. indet.) and a small notoungulate (Mesotheriidae, Microtypotlierirmi cf. M. choquecotense) (MacFadden et al., 1990). A magnetostratigraphic study and an associated fission-track date of 6.9 k 1.1 Ma, indicate that these rocks and fauna span fToin - 7.5 - 6.7 Ma (MacFadden ef al., 1990), making thein late Huayquerian.

Remains of Notoungulata (Mesotheriidae, Plesiofyi~oflieriuni) havc bccn collcclcd from two localitics of thc Quehua Foi inat ion S.S. to thc east-southcast of Quchua in the southern part of the Altiplano (Villarroel, 1978, p. 166; Hoffstcttcr & Villarroel, unpublished as cited in Marshall et al., 1983, p. 43). Plesiotypotheririni cf. P. niajrts or niinrrs and scutes of Dasypodidae were collected from approximately 3 km southeast of Quehua; and cf. P. achirense was collected approximately 7 km southeast of Quehua (the first locality is from a level 40 ni stratigraphically higher than the second). Rodentia (Caviidae, Dolichotinae, Orflioniycfera sp.) are also recorded from Quehua (Hoffstetter, 1986, p. 222). The presence of these taxa establishes that the Quehua Formation at these localities is temporally equivalent to the Mauri 6 and Rosa Pata, formations

In summary, the large herbivqres in Huayquerian faunas on the Altiplano include Mesotheriidae (Plesiofypolheriunz), Toxodontidae (medium-sized Toxodontinae and a large forni with a frontal horn), several ground sloths, Glyptodontidae (Sclerocalyptinae) and large Dasypodidae (Pampatheriinae) (Hoffstetter, 1986, p. 236).

There are four additional mammal-baring faunas of possible or reputed Huayquerian age in Bolivia, yet all need confirmation.

First, an edentulous skull of a Mesotheriidae (aff. Plesiotypofheririm achirense) was recently collected from the poorly known Casira Formation to the southeast of the pueblo Casira on the southwest side of Cerro Khellu Khakha Loma, Modesto Omiste Province, department of Potosí, near the Argentine,border in southernmost Bolivia (Anaya et al., 1989).

Second, is a fauna from the "Estratos Muyu Huasi" at Muyu Huasi, about 50 km northeast of Sucre in southcentral Bolivia. The taxa include: Edentata (Dasypodidae, cf. Doellofafus sp., cf. Paleupltracfus sp.; Mylodontidae, gen. et sp. indet.), Litopterna (Proterotheriidae, gen. et sp. indet.), Notoungulata (Hegetotheriidae, Pseridohegetotlteriunt sp.; Interatheriidae, Profypoflieriuni sp.) and caviomorph Rodentia (Abrocomidae, Profabroconta sp.; Caviidae, ?Orflioniycfera sp., ?Cardionlys sp.; Chinchillidae, Lagosromopis sp.; Dinoinyidae, gen. et sp. indet.; Eretliizontidae, gen. et sp. indet.; Octodontidae, cf. Sciamys sp.) (Villarroel & Marshall, 1989).

Third, is the fauna from the Cobija Formation collected along the Río Acre between Cobija and Bolpebra, department of Pando in northwest Bolivia. The vertebrates include fish (Chondrichthyes), reptiles (Chelonia, P odocnenzis sp.; Crocodilia, Gavialosrcclius sp.), birds (indet.), and mammals (Rodentia indet.) (Carrasco, 1986). The jaw of an enormous crocodile was collected from this same formation at Candelaria, to the west of Riberalta along the Río Madre de Dios (Leytón & Pacheco, 1989).

And fourth, a CTagment of a right dentary witli well preserved M* and M' of cf. Psertdoliegefoflieriuni sp. (Notoungulata, Hegetotheriidae) was recently collected at the Estación Abaroa, about 25 km east-northeast of Charaíía, department of La Paz, The specimen is in GEOBOL collections in La Paz and has the catalogue number GB-089 (C. Villarroel, personal communication, 1990).

EARLY AND MIDDLE PLIOCENE (Monteliennosan-Cliapadinalalaii)

The most important mammal fauna of Montehermosan age i n Bolivia is from tlie Umala Formation at and near Ayo Ayo (3800 in), Vizcacliani and Umala, 65-75 km south of La Paz. A tuff from the base of the Umala Formation (toba 76) has yielded mean radioisotopic dates of 5.4 Ma (Evernden ef al., 1966, 1977; Lavenu c/ al., 1989; Marshall et al., 1992). whilc thc Ayo Ayo tuff in thc top of this foriiiatioii has yicldcd a iiiean age of 2.8 Ma (Lavenu CI al., 1989; Marshall et al., 1992). The fauna includes: Marsupialin (Didelphidae, Sparassocyniiiae, Sparassocynrrs lieterotopicrrs; ?Caeiiolestidae; Argyrolagidae, Microtragrrlrrs bolivianrrs), Edentata (Dasypodidae. Pampatheriinne, cf. Plaina sp., Euphractinae, Macroeirplzractiis sp.; Megatheriidae, cf. Megt~lieriiinr; Mylodontidae, Mylodontinae), Notouiigulata (Toxodontidne, Xotodontinae, Posnanskytlieriiini desagrraderoi), Litopterna (Macraucheniidae, cf. Proniacrauclienia sp.), and cavioniorph Rodentia (Octodontidae, Ctenomyinae, Praecfenoniys rhonibidens, P. vagus; Chinchillidae, Lagostominae; Caviidae, Caviinae;

fartlier to the north. ' Hydrochoeridae. Cltapalntarlieriuni saavedrai) (Liendo-Lazarte,

638

FOSILES Y FACIES DE BOLMA -VOL 1 VERTEJHUDOS

$GE M ~ )

SOUTH AMERICAN A L T I P L A N

& LANDMAMMAL AGE GLACIATIONS GLACIAL LAKES

I- 1.04 : I ENSENADAN I Kaluya

:ORDILLERA ORIENTAL (Central 1

Cabana

CHACO

Mataro * !Purapurani T. 1.6Ma

2.5

30 MONTEHERMOSAN Umala Fm.*

3 ASSOCIATED FORMATIONS

Ulloma Fm.*

Charaña Fm.* - ? - ? - ? -

Pérez Ign.2.8Mr:

OCHABAMBP

Anzaldo *

Anzaldo *

Anzaldo * Sacaba I *

1 i;luapua~* Tari)o*, Padcayo *,

ConceEcn2- ------ -----

Betanzos * r------j American Faunal Interchange

Figure 3. Chronostratigrapliic chart showing late Pliocene-Pleistocene (Uquian-Lujanian) South American Land Mammal Ages (modified after Marshall, 1985) and principal vertebrate-bearing formations (*) discussed in text. Geologic time scale follows

Berggren et al. (1985).

1943; Hoffstetter, 1986; Hoffstetter et al., 1971, 1984; Hoffstetter & Villarroel, 1974; Villarroel, 1975, 1977; Villarroel & Marshall, 1983).

Numerous mammals have been collected from the La Paz Formation around La Paz at Achocalla, Alto Obrajes, Alto Següencoma, Calacoto, Gualberto Villarroel, Kenko and Tembladerani. This formation consists of some 700 m of fine to coarse sediments of fluvial to fluvio-lacustrine origin (Lavenu et al., 1989) which Dobrovolny (1962, pp. 20-27) subdivided into three units (lower, middle, upper). The fossils are from below a tuff (toba Chijini) in the upper part of the La Paz Formation which has yielded a mean radioisotopic date of - 2.8 Ma (Clapperton, 1979; Lavenu el al, 1989; Marshall et al., 1992). This tuff appears to belong to the same ignimbrite flow that deposited the PCrez Ignimbrite and Ayo Ayo tuff (see above). Dates of - 5.5 Ma have also been obtained on a tuff (= toba Cota Cota) in the lower part of this formation at Cota Cota, southeast of La Paz (Lavenu et al., 1985, 1989; Servant et al., 1989). This tuff seems to belong to the same event that deposited the Jankhomarka tuff (= toba 76), which apparently correlate with collapse and eruption of the Soledad Caldera at 5.4 Ma (Redwood, 1987), but was probably emitted somewhere in the western Cordillera as suggested by its thickness increasing toward the west. A magnetostratigraphic study of the La Paz Formation shows that deposition of the middle and uppe; units occurred during the Gauss epoch (i.e. 3.4 to 2.48 Ma) (Thouveny & Servant, 1989). The fauna includes: Edenlata (Dasypodidae, Euphractini, Macroertphractus aff. nioreni; Glyptodontidae, Sclerocalyptinae, cf. Sclerocalypfus sp., cf. Plolrophorops; Megalonychidae, gen. nov.), Notoungulata (Toxodontidae, Xotodontinae, Posnanskytkeriitm desagrraderoi, P . nov. sp.) and Litopterna (Macraucheniidae, cf. Proniacrauchenia sp.) (Ahlfeld & Branisa, 1960, p. 135; Clapperton, 1979; Radelli, 1964, p. 842; Hoffstetter, 1986; Villarroel, 1977; Villarroel & Graf- Meier, 1979; Mones & Mehl, 1990). The vast majority of these fossils are from Dobrovolny's (1962) middle unit (Mones & Mehl,

A few vertebrates have been collected from north of Pomata Ayte, 1990, p. 22).

about 200 km south of La Paz, from rocks designated as the Formación Mauri (Hoja 6038, Corque; Hoja 6039, Choquecota; see Hoffstetter et al., 1972, Fig. on p. 740) which unconformably overlie the Huayquerian age Rosa Pata Formation (see above) or more specifically its terminal facies, the Conglomerado Pomata, which has a K-Ar date of 6.4 Ma obtained on a rhyolite (Evernden et al,, 1966, 1977; Marshall et al., l9!3, p. 78). The fauna occurs aboqe a tuff which may represent the toba Jankhomarka (Martinez, in Marshall et al., 1983, p. 78) and includes: Notoungulata (Toxodontidae, Xotodontinae, Posnanskytheriuni desaguaderoi), Litopterna (Macraucheniidae, cf. Pronaacrauchenia sp.), Edentata .(Mylodontidae), caviomorph Rodentia, and a large terrestrial carnivorous phororhacoid bird (Hoffstetter et al., 1972; Hoffstetter, 1986).

From the Remedios Formation at Cerro Canasa near Corque and at Orinoca south of Oruro are reported remains of Edentata (Mylodontidae), Notoungulata (Toxodontidae, Xotodontinae, Posnanskytherium sp.), and Litopterna (Macraucheniidae, cf. Pronzacrauchenia sp.) (Lavenu, 1984; Hoffstetter, 1986) from above a tuff with dates of 5.2 - 4.6 Ma (Marshall et al., 1992). This formation is locally separated by an angular unconformity from the overlying mammal-bearing "lacustre Minchín" of late Pleistocene age (see below).

A Montehermosan age for the mammal faunas from the Umala, La Paz, Remedios and "Mauri" (at Pomata) formations is established on faunal content and radioisotopic dates. These Pliocene faunas differ markedly from those of the late Miocene (Mauri 6, Rosa Pata, Quehua formations) on the Altiplano by the absence of Mesotheriidae and in the predominance of Macrkheniidae (cf. Proniacrauchenia sp.), other Toxodontidae (Xotodontinae, Posnanskytlterium sp.), other Edentata (Megatheriidae; Mylodontinae; Pampatheriinae, Kraglievichia sp., Plaina sp.), and Hydrochoeridae (Chapalmatkeriuni sp.) (Hoffstetter, in Marshall et al., 1983, p. 44; Hoffstetter, 1986). Furthermore, these faunas are bracketed below by the 5.4 Ma toba Jankl>omarka from the base of the Umala Formation and the - 5.5 Ma Cota Cota tuff in the lower part of the La Paz Formation, and above by the 2.8 Ma Chijini tuff in

639


the upper part of the La Paz Formation and 2.8 Ma Ayo Ayo tuff in the top of the Umala Formation.

There are three other reports of possible early to middle Pliocene age m a m m a l f aunas in Bo l iv i a , a l l o f which need confirmation.

First, Pachynodon validus Burmeister (1 892, pp. 433-434) (Notoungulata, Toxodontidae) is probably from Bolivia and may be of Pliocene age. As noted by Simpson (1940, p. 705), 'I ... the only available information as to provenience is that the specimen was sent to Vaca Guzmán Blanco (the Bolivian Minister in Buenos Aires) from Santa Cruz de la Sierra, Santa Cruz, Bolivia. The implication is that the specimen was found at that place, but this is not definitely established".

Second, Montañ0 (1968) described a mammal fauna from Anzaldo (3000 m), about 55 kni southeast of Cochabamba, which he assigned to the Pleistocene, A later visit to this locality by Hoffstetter, Montaiio and Ortega resulted in recovery of a specimen of cf. Proniacrarrclienia sp. (Notoungulata, Macraucheniidae) from a 2 m- thick siltstone in the lower level at Quebrada Tijascka, about 3 km southwest of Anzaldo. This is a small macraucheniid and is of Pliocene aspect (Hoffstetter, in Marshall et al., 1983, p. 44). A true Pleistocene mammal fauna occurs at the same localitiy (see below).

And third, from, a rock unit informally called "lac de Sacaba" or "Sacaba 1" (Lavenu, 1986, pp. 114-1 15) south of Sacaba in the area of Laba-Laba Alta (Quebrada Fierro Churu) about 18 km east- southeast of Cochabamba, were recovered remains of mammals identified by Villarroel (in Mancilla, 1979, p. 32) as Plohophorus sp. (Edentata, Glyptodontidae).

LATE PLIOCENE (Uquian)

There is only ode potential fauna of this age in Bolivia. It is from near Anzaldo, about 55 km southeast of Cochabamba. In Quebrada Tijascka, 3 km southwest of Anzaldo, Montaiio (1968) recovered a complete caudal tube of Prodaedicurus cf. P . divincenzi (Edentata, Glyptodontidae) identified by Hoffstetter (in Marshall et al., 1984, p. 36) from a gravel layer. This is the only record of Prodaedicurus for Bolivia, a taxon originally described from beds designated as the "Piso Castellanosense" in Uruguay, the age and faunal content of which are discussed by Mones (1979, pp. 16-17). Mammals of possible Monteheimosan (see above) and Pleistocene (see below) age are also known from Anzaldo.

L A T I C T 15R3'1 A KY

I I

I

~~ ~~

FOSILES Y FACIES DE BOLIVIA - VOL. I VERTEBRADOS

Figure 4. Map of Bolivia showing vertebrate localities of Eocene-Pleistocene age.

64 1


later papers on this collection were provided by Kraglievich (1928, 1930b), Cabrera (1929, 193 l), and López Aranguren (1930). In 1902 Nordenskiöld sent a small collection to Uppsala, Sweden which resulted in publications by Nordenskiöld (1902, 1903) and Sefve (1912, 1915b). A large collection of specimens purchased in 1903 by the Marquis de Créqui-Montfort and E. Sénéchal de la Grange from the Echazú family was donated to the Muséum National d’Histoire Naturelle, Paris and served as the basis for the now classic monograph by Boule & Thévenin (1920) (see also Cottreau, 1921); the stratigraphy was described by Mortillet (1922), a member of the 1903 expedition. Between 1894 and 1915 members of the Echazú family of Tarija made an impressive private collection of fossil mammals from Tarija and surrounding areas @chazÚ, 1905, 1921). Some of these fossils were sold to various foreign institutions (see above, below), although the major part of the collection, consisting of some 2,630 specimens which remain virtually unstudied, was sent to La Paz in the 1930s. In 1977 part of this collection was returned to Tarija and deposited in the Museo de la Universidad de Tarija; it is planned that the remainder of the collection will be returned to Tarija in the ilex future (Takai ef al., 1982, 1984). In 1924 and 1927 expeditions from the Field Museum of Natural History, Chicago under the direction of E. S. Riggs made a spectacular collection from Tarija and Padcaya, and purchased some specimens from the Echazú family (Riggs, 1928, 1930); this magnificent collection remains virtually undescribed (Marshall, 1978). During 1978 and 1980 paleontologists from the Research Institute of Evolutionary Biology, Tokyo made a small collection which was taken to Japan (Takai et al., 1982, 1984). The most recent work by foreign researchers was carried-out by a team from the University of Florida, Gainesville in 1980 and 1986 (MacFadden, 1981; MacFadden & Azzaroli, 1987; MacFadden & Wolff, 1981; MacFadden ef al., 1983; Frailey et al., 1980).

A history of the debated age of the Tarija fauna is provided by Marshall et al. (1984). Ameghino (1902) and Boule & Thévenin (1920) regarded the fauna as Pliocene; Rovereto (1914) assigned it to a new land mammal age, the Tarijense; Kraglievich (1930a, 1934) stressed the post-Ensenadan (s.s.) and pre-Lujanian (s.s.) aspect of the fauna which means that it is comparable to the Bonaerense as defined in Argentina (see Marshall ef al., 1984, Fig. 1). Palterson & Pascua1 (1972, p. 249) regarded the fauna as Lujanian, while Webb (1974, p. 176) considered it Ensenadan. This debate was resolved, at least in part, by MacFadden et a l . (1983) who provided a geochronologic study of the - 250 m-thick Tarija Formation in the Tarija basin using magnetostratigraphy and radioisotopic dating. They show that this formation spans a time interval between 1.0 and 0.7 Ma, or perhaps younger, making this fauna late Ensenadan by current standards. ‘I‘akai et al. (1982, p. 5) report dates of 0.25 - 0.20 Ma on some fossil bones using electron spin resonance technique, but these dates are at odds with the more secure conclusions of MacFadden et al. (1983). Nevertheless, Hoffstetter (1986) cautions that some fossils from upper levels of the Tarija Formation may be younger, perhaps early Lujanian in age. It is apparent that additional detailed stratigraphic studies of the type provided by Oppenheim (1943), additional magnetostratigraphic and radioisotopic studies as provided by MacFadden et al. (1983), and more refined systematic and biostratigraphic studies of the faunas from Tarija, Concepción and Padcaya are needed to establish the absolute and relative ages of the numerous fossil levels.

This fauna is in dire need of a systematic revision. In addition to the papers cited above, the mammals are discussed by Berta (1981, 1985,,1987, 1988), Liendo-Lazarte (1946) and Hoffstetter (1963a, b, 1968a, 1986). The following taxa appear to be securely identified: Marsupialia (Didelphidae, Lutreolina crassicaudata), Edentata (Dasypodidae, Chaetophractus tarijensis, C . villosus, Eupliractus sexcinctus, Propraopus cf. sulcatus or grandis, Pampatherium cf. Itumboldti or typum; Glyptodontidae, Chlamydotherium cf. sellowi, Glyptodon ret iculat us, Hop loplwr us ecliazui, Neothoracopliorus cf. elevatus, Panoclitus cf. tuberculatus; Megalonychidae, Nothropiis tarijensis; Megatheriidae, Megatherium tarijense; Mylodontidae, Glossotheriuni tarijense, Lestodon armat us, Scelidodon tarijensis), Rodentia (Cricetidae, Andinomys cf. edea, Calomys cf. lancha, Kunsia fronto, Necfoniys cf. squamipes, Oxymycterus cf. paranensis, Pltyllotis cf. darwini; Octodontidae, Ctenonzys subassentiens, C . brachyrhinus; Echimyidae, Euryzygpmatomys hoffstetteri; Myocastoridae, Myocastor perditus; Erethizontidae, Coendou magnus, C . sp.; Caviidae, Cavia sp., Galea cf. musteloides; Hydrochoeridae. Hydrockoerus sp., Neoclioerus tarijensis), Carnivora (Canidae, Canis dilus, Cltrysocyon brachyurus, Pseudalopex gymnocercus, Theriodictis tarijensis, Protocyon troglodytes; Ursidae, Arctodus tarijensis, A . wingei; Procyonidae, Nasua sp.; Mustelidae, Conepatus suffocans; Felidae, Felis concolor, F. yaguaroundi, Panthera onca, Sniilodon populator), Litopterna (Macraucheniidae, Macrauchenia patachonica), Notoungulata (Toxodontidae, Toxodon cf. platensis), Proboscidea (Gomphotheriidae, Cuvieronius liyodon, NotiomastÓdon sp., Haplontastodon or Stegopiastodon sp.), Perissodactyla (Equidae, Equus insulatus, Hippidion principale, H . bonaerense, Onohippidiuni devillei; Tapiridae, Tapirus tarijensis), Artiodactyla (Tayassuidae, Platygonus tarijensis; Camelidae, Lama cf. onteni, L. glania, L . provicugna, Palaeolania sp.; Cervidae, Charitoceros tarijensis, Hippocamelus sp.). Undescribed specimens of fish and reptiles are reported by Hoffstetter (1963~1, pp. 201-202); frogs (Bufonidae, Bufo cf. niarinus liorribilis; Leptodactylidae, Ceratoprys sp.) from Tarija are described by Vergnaud-Grazzini (1968); buds (Ciconiiformes, Vulturidae, Vultur gryplius = V . pratruus Lönnberg, 1905; see Emslie, 1988) and undescribed specimens of birds are known from Tarija (locality of Turumayu, in Peabody Museum, Yale University) and Padcaya (Villarroel, in Marshall et al., 1984, p. 33; specimens also in Peabody Museum, Yale University).

LATE PLEISTOCENE-HOLOCENE (Lujanian-Recent)

A faana of large body-size mammals of possible early Lujanian age has long been known from the now classic locality of Ulloma (3880 m), situated about 40 km south of Corocoro on the south side of the Rio Desaguadero. The fossils are from the Ulloma Formation which consists of well stratified fine-grained sands rich in calcareous nodules; it is bounded below by an undated tuff, above by a diatomite, and rests unconformably on the folded Totora Group (late Miocene). The Ulloma Formation was apparently deposited during retreat of the Sorata glaciation as part of Lake Ballivian, an ancient southern extension of Lake Titicaca (Servant & Fontes, 1978; Hoffstetter, 1986, p. 224; Hoffstetter, in Marshall et al., 1984, p. 35). The fauna includes: Edentata (Glyptodontidae, Glyptodon sp.; Megatheriidae, Megatherium cf. americanum, Megatherium

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FOSDXS Y FACLES DE BOLMA - VOL. I VERTEBRADOS

(Pseudomegatherium) medinae = M. sundti; Mylodontidae, Sceli#odon cltìliense Lydekker 1886 = Scelidotheriunt? bolìvianum), Litopterna (Macraucheniidae, Macraucltenia ullontensis), Proboscidea (Gomphotheriidae, Cuvieronius ltyodon = Mastodon bolivianus), and Perissodactyla (Equidae, Onoltippidium (Paraltipparion) bolivianuni = Scelidotlterium? compressunt) (Sundt, 1900; Philippi, 1893a, b; Pompeki, 1902; Oliver, 1934; Sefve, 1914, 1915a, b; Douglas, 1914; Kozlowski, 1923; Casamiquela & Sepúlveda, 1974; Ahlfeld & Branisa, 1960; Servant & Fontes, 1978; Hoffstetter, 1986; Marshall & Salinas, 1991). A recently discovered fauna at a locality 4 km west of Carsani is also probably from the Ulloma Formation, and the taxa include: Edentata (Mylodontidae?, Megatheriidae), Notoungulata (Toxodontidae), Perissodactyla (Equidae), and Rodentia (R. Céspedes, personal communication, 1989).

The richest Lujanian fauna in Bolivia is from Ñuapua, between Carandaití and Capiranda. Hermann (see Schiller, 1913, p. 180, n2) first reported mammals from this locality, and Bonarelli (1921, p. 80) later recorded mastodonts and other mammals. Hoffstetter (1968a) published the first study on the stratigraphy, sedimentology and vertebrate paleontology based on work he did with L. Branisa between 1962 and 1965. MacFadden & Wolff (1981) made a similar study based on wdrk done in 1978.

The Ñuapua Formation consists of 9 m of sediments which rest unconforinably on non-fossiliferous gray and red clays of the Tertiary age Chaco Series. Hoffstetter (1968a) divided the Ñuapua Formation into three members (from oldest to youngest, Ñuapua 1, Ñuapua 2, Ñuapua 3) based on color of sediments and faunal content. MacFadden & Wolff (1981) provide a magnetostratigraphic study of the Ñuapua Formation and show that all three members are located within the Brunhes Normal chron which begins at 0.73 Ma and are thus Lujanian in age or younger (see below).

The lower Ñuapua 1 member, which consists of 2-3 m of pink to reddish consolidated cinerite, is probably the level from which mammals were collected by early workers. The fauna (see Hoffstetter, 1968a; MacFadden & Wolff, 1981; Berta, 1981, 1985, 1987, 1988) includes: Reptilia (turtles, Chelonia, Testudinidae, large Chelonoidis sp., a small testudinid? and an undetermined chelid?; Broin, 1991). Edentata (Dasypodidae, Panipatlterium sp.; Glyptodontidae, Chlamydotherium sp., Glyptodon cf. reticulatus, Panoclitus cf. tuberculatus, Sclerocalyptus cf. ornatus; Megalonychidae, cf. Notlirotlterium sp.; Megatheriidae, Megatherium cf. americanum; Mylodontìdae, Mylodon darnhi), Rodentia (Hydrochoeridae, Hydrocltoerus cf. hydrocltoeris; Ctenomyidae; Capromyidae; Cricetidae; Octodontidae), Carnivora (Canidae, Protocyon troglodytes, Pseudalopex sp.; Ursidae, Arctodiis sp.; Felidae, Panthera onca, Smìlodon popiflator), Litopterna (Macraucheniidae, Macraucltenia cf. patacltonica), Notoungulata (Toxodontidae, Toxodon ensenadensis), Proboscidea (Gomphotheriidae, Stegomastodon sp.), Perissodactyla (Equidae, Equus curvidens, Hippidion sp.), and Artiodactyla (Camelidae, Palaeolama sp.; Tayassuidae; Cervidae). The Ñuapua 1 fauna is clearly of Lujanian age.

The middle Ñuapua 2 member consists of 1.5 - 1.0 m of reworked gray tuff. This fich fauna, discovered by L. Branisa in 1955, includes: frogs (Bufonidae, Bufo cf. paracnemis; Leptodactylidae, Leptodactylus cf. ocellatus, Ceratrophrys cf. ornata), reptiles (Teiidae, Tupinambis teguixin; Amphisbaenidae, Leposternon sp.;

Boidae; Colubridae, Colubrinae; Viperidae, Crotalinae; undetermined turtles), birds (Rheidae, Rhea cf. americana; Podicipidae, Podiceps minor, P . cornutris; Plataleidae, Plareleu sp.; Ajaja rosea; Anseridae, Dendrocygna sp., Anas sp.; Rallidae; Jacanidae, Jacana sp.; Tinamidae, Cryptiirus lataupa, cf. Rltynclrotus sp.; Columbidae; Falconidae; Cuculidae, Coccyzus sp.; Caprimulgidae, Nyctibus sp.; Passeriformes); the mammals include Chiroptera (Molossidae, Euntops perotis), Edentata (Dasypodidae, Chaetopliractus cf. vellerosus or villosus, Zaedyus pichiy , Dasypus cf. novenicinctus, Eupltractus sexcinctus, Tolypeutes matacus, Propraopus cf. punclatus), Rodentia (Cricetidae, Caloniys sp., Graomys sp., Holochilus brasiliensis, Zygodontomys lasiurus; Octodontidae, Ctenomys sp.; Myocastoridae, Myocastor coypus; Chinchillidae, Lagostomus maximus; Caviidae, Galea cf. musteloides; Capromyidae; Hydrochoeridae, Hydrochoerus hydrocltaeris), Lagomorpha (Leporidae), Carnivora (Canidae, Dusicyon griseus), Artiodactyla (Cervidae, Morenelapltus sp.), and a human skull (Hoffstetter, 1968a; MacFadden & Wolff, 1981; Vergnaud-Grazzini, 1968; Marshall et al., 1984). A carbon-14 date of 7200 f 400 yrbp was obtained on the human skull, and another date of 6600 f 370 yrbp was obtained on unspecified associated mammal bones (MacFadden & Wolff, 1981; Marshall el al., 1984, p. 34). Some fossils of extinct megafauna ( i . e . Glyptodontidae, Scelidodon, Toxodon, Palaeolama, and mastodonts) were recovered from the Ñuapua 2 member, but aspects of their preservation suggest that these specimens were reworked from the Ñuapua 1 member and are thus not contemporaneous with the rest of the Ñuapua 2 fauna (Hoffstetter, 1968a, pp. 832-833; but see MacFadden & Wolff, ,1981 who did not recognize this fact). Thus, the carbon-14 dates and the absence of securely associated megafauna suggest that the Ñuapua 2 fauna is Holocene in age.

Hoffstetter (1968a, p. 834) reports the recovery of an ulna of Toxodon sp. from the basal contact of Ñuapua 3 with the underlying Ñuapua 2, but not within the Ñuapua 3 tuff which is otherwise unfossiliferous and which MacFadden & Wolff (1981) regard as Quaternary alluvium. This specimen was also probably reworked from Ñuapua 1.

PLEISTOCENE sensu lato (Ensenadan-Lujanian)

There are numerous other scattered reports of Pleistocene mammals in Bolivia, but the known specimens have been little studied and for many their age and stratigraphic context have yet to be securely established.

On the Altiplano at La Paz and Tambillo (west of La Paz) have been collected remains of mastodonts and glyptodonts (Hoffstetter, 1986). "Pleistocene fossils" have also been reported at San Andrés and Achiri (Cantón Achiri, i.e. at Challncollo and Huana Jahuira), although the exact stratigraphic position and identification of these fossils need confirmation (Hoffstetter, 1986, p. 224). Furthermore, the reputed Pleistocene fossils at Achiri may, in fact, represent a confusion with those from theqlate Miocene Mauri 6 Formation (Hoffstetter, 1986, p. 224). A glyptodont carapace (now in GEOBOL, La Paz) was collected by Anaya (1988) from the Comunidad Segueri, about 1.5 km east of Tiahuanacu; a possible Megatherium sp. was collected in 1985 about 600 in to the southwest of the ruins of Tiahuanacu (Anaya. personal

643

communication, 1989); and L. Branisa (correspondence now in Peabody Museum, Yale University) records a fossil horse (Equidae) from at or near Tiahuanacu.

On the western slope of the Cordillera Oriental, about 110 km southeast of La Paz, have been recorded remains of Panthera onca at Yaco (3600 m) and Macrauclzenia sp. at Puchuni (Hoffstetter, 1986, p. 226). Kozlowski (1923) records discovery by miners of "Pleistocene mammals" from Calacoto, Cuesta de Chacarilla and Paria; while Lavenu (1984) records camelids (Camelidae) and L. Branisa (unpublished notes) records remains of artiodactyls and a horse from Culluri near Corque, southwest of Oruro. Mastodonts are reported from northwest of Oruro, from Paria (16 km northeast of Oruro), and from Pampa Aullagas on the southwest bank of Lake PoopÓ opposite Créqui-Montfort Island (Hoffstetter, 1986, p. 224). Ahlfeld & Branisa (1960, p. 165) report remains of a mastodont tusk and a lower jaw of Hippidion from "las minas de estaño de Carguaycollo, en la Cordillera de los Frailes" (4100 m); the identification of the horse needs confirmation (Hoffstetter, 1986, p. 226) and it is possibly referable to Onohippidiuai.

Near Anzaldo on the east slope of the Cordillera Oriental, about 55 kin southeast of Cochabamba, Montañ0 (1968) recovered a Pleistocene mammal fauna from sands, silts and gravels in an upper level at Quebrada Tijascka, 3 km southwest of Anzaldo. This fauna is from a level above the Uquian age gravel unit with Prodaedicurus (see above), and includes: Edentata (Glyptodontidae, Glyptodon sp.; Megatheriidae, Megatlteriuni sp.), Proboscidea (Gomphotheriidae, Cuvieroniris sp.), and Artiodactyla (Camelidae, Lama sp.) (Hoffstetter, in Marshall et al., 1984, p. 36; Hoffstetter, 1986; p.

Ahlfeld & Branisa (1960, p. 167) record fragment5 of glyptodonts from along the Río Rocha near Sacaba about 7 km east-southeast of Cochabamba, and R . Céspedes and R. Suarez (personal communication, 1989) recovered remains of glyptodonts and camelids in 1986 from along the Río Loro Mayu, just south of the Río Rocha, about 10 km east-southeast of Cochabamba. Reports of mastodonts and glyptodonts from near Sacaba and Cliza in the Cochabamba-Sacaba basin (2600-2800 m), and of mastodonts in the Padilla basin (2120 m) (which has a tuff dated at 3.36 k 0.3 Ma) are given by Hoffstetter (1986, p. 226). A femur of an edentate is also known from near Toco (R. Céspedes, personal communication, 1989).

Near Sucre in the small Sucre basin (2800 in) "esti ubicada una meseta que constituye la línea divisoria de Ias aguas entre los ríos Pilcomayo y Grande" where remains of Glypfodon sp. have been found (Ahlfeld & Branisa, 1960, p. 167; Hoffstetter, 1986, p. 226). This meseta is part of the San Juan.de1 Oro planation surface (see above) and the fossils are from its associated deposits.

In the Betanzos basin (3390 in) between Potosí and Sucre have been found remnids of Edentata (Glyptodontidae, Sclerocalyptinae, Panochrltus sp.), Proboscidea (Gomphotheriidae, Cuvieronius Ityodon = Mastodon andinun!), Perissodactyla (Equidae, gen. et sp. indet.), and Artiodactyla, (Cervidae; Camelidae) (Pick, 1944; Hoffstetter, 1986, p. 226). About 4 km to the south of Betanzos have been collected Mylodontidae?, Glyptodontidae, Gomphotheriidae and Equidae which are now in the Universidad Tomis Frías, Potosí (Anaya, personal communication, 1989). At Khoña-Paya near Betanzos, were collected remains of Equidae from between a tuff dated at 1.9 Ma in the base of the section and another tuff dated at

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644

less than 1.0 Ma near the top of the section (Servant et al., 1989). A mastodont has recently been found at the pueblo of Salitre, situated to the east of Villazon near the Argentine border in southernmost Bolivia (reported by Ing. Camacho to F. Anaya, personal communication, 1989) and remains of glyptodonts are known from Mojo (R. CBspedes, personal communication, 1989). All these fossils come from sediments related to the San Juan del Oro planation surface.

In the Amazonian region at Fortin Madidi on the Río Madidi and at Cara Cara on the Río Maniqui (in the region called Yucumo- Maracas near San Borja) in the Río Beni basin have been found remains of Toxodontidae in the former and Mixotoxodon sp. in the lalter (Hoffstetter, 1968a; Hoffstetter, in Marshall el al., 1984, p. 36; Anaya, personal communication, 1989). Further to the southeast, d'Orbigny (1842, p. 205) recovered a collection of bones of large mammals "en las barrancas cerca de la confluencia de los ríos Piray y Grande" which were lost during the same expedition "en un vuelco de la canoa" (Ahlfeld & Branisa, 1960). In the Río Piray basin at Santa Rosa north-northwest of Santa Cruz and to the southwest of Santa Cruz, Hoffstetter (1968a) recovered mastodont teeth in 1960. Remains of mastodonts have also been recovered by L. Branisa (unpublished) from Quebrada Chorrillos, about 12 km northeast of Charagua, and Trujillo (1984) reports Cuvieronius andiuni from the Valle de Carohuaycho, 28 km north-northeast of Camiri and 30 km west of Charagua.

EVOLUTION OF THE BOLIVIAN LAND MAMMAL FAUNA

There are four interrelated phenomena that were of profound importance in influencing and/or determining the taxonomic composition of late Cenozoic land mammal faunas in Bolivia: Andean uplift and related climatic changes, glaciations, the Great American Faunal Interchange, and megafaunal extinctions.

1. Andean uplift and relaed climatic changes. The main climatic effect of the central Andean uplift in Bolivia was the creation of: (a) a rain shadow that prevented the northeast-proceeding moisture-rich winds to reach the coastal areas of southern Peru and northern Chile, and (b) dry "high"-altitude climates on the Altiplano and adjacent cordilleras.

As demonstrated by geomorphological studies in southernmost Peru, uplift began - 20 Ma, but considerably decreased in this area by - 8 Ma (Tosdal ef al., 1984). According to Benjamin et al. (1987), uplift rates of the Bolivian Cordillera Real were about 0.1 - 0.2 mm/yr between 40 and 20 Ma, and increased significantly between 15 and 10 Ma to reach values perhaps as high as 0.7 mm/yr by 3 Ma. Hyperarid conditions, due to a permanent rain shadow, became established in northern Chile (24" S) in middle Miocene time (Alpers & Brimhall, 1988). Middle Miocene climatic dessication in northern Chile and southern Peru was accentuated by oceanic cooling related to the contemporaneous development of the Antarctic ice cap (Alpers & Brimhall, 1988), and this must also have liad some influence on Altiplano climates. Although it is difficult to calculate precisely the paleoaltitudes of the central Andes at a given time, it seems that the mountain belt had attained at least half its present elevation prior to about 15 Ma (Alpers & Brimhall, 1988). It is likely that in Bolivia, Andean uplift was accelerated by the

~- - -

POSILES Y FACIES DE BOLIVIA - VOL. I VERTEBRADOS

tectonic load produced by the first major tectonic crisis (see above) starting at about 27 Ma. However, there may have been more than one uplift mechanism subsequent to 45 Ma.

Thus, the significant elevation of the central Andes during at least the past 20 Myr must have influenced the land mammal fauna in two ways. First, the rising central Andes came to serve as a barrier to‘the moisture-rich northeastem winds, resulting in the formation of a rain shadow effect along its western flank. Second, ecological changes resulted from the uplift, and true desert, high montane and extensive grassland habitats at lower elevations came into existence during this time. These ecological changes provided new evolutionary opportunities for taxa which could adapt to colder high-elevation habitats, and caused other taxa to abandon these emerging environments in favor of more hospitable warmer environments at lower elevations. For example, Mesotheriidae disappeared from the Altiplano at the end of Huayquerian time, and Hydrochoeridae and Pampatheriinae disappeared from high-elevation faunas at the end of Montehermosan time (Hoffstetter, 1986).

The net result of Andean uplift is that it produced markedly diverse geographic regions in Bolivia and many of the differences seen particularly in Pleistocene faunas can be attributed to elevation and hence ecologies. As examples, some Pleistocene taxa apparently thrived at elevations of 3800-4000 m (i.e. Megatherium, Scelidodon, Macraucltenia, Cuvieronius, Onohipyidium, Lama, Pantliera, Glypfodon) and occur at low elevations as well; other taxa (i.e. Palaeolama, Equus) are unknown above 3300 m; while others are either unknown or extremely rare above 2000 m (i.e. Toxodontinae, Pampatheriinae, Dasypodinae, Hydrochoeridae, Erethizontidae, Dasyproctidae, Agutidae, Dinomyidae, Echimyidae, Tapiridae, Tayassuidae, most Cervidae, Haplomastodon, Chrysocyon, Smilodon) (Hoffstetter, 1986).

2. Glaciations. Four major Pleistocene glaciations in Bolivia are recognized by Servant & Fontes (1978) (from oldest to youngest: I Calvario, II Kaluyo, III Sorata, IV Choqueyapu 1 and 2). A tuff (Purapurani tuff = toba Sopari of Thouveny & Servant, 1989, p. 332) interbedded within the glacial and interglacial deposits that overlie the Calvario Drift, has yielded a K-Ar date of 1.6 Ma (Lavenu et al., 1989). A fifth glaciation called the Patapatani (Hoffstetter, 1986) is reported in Pliocene sediments from below the Chijini tuff (which has a mean age of 2.8 Ma; Lavenu et al., 1989; Marshall ef al., 1992) of the La Paz Formation.

During times of glacial advance, ice sheets extended to about 1000 m below their present day limits (Hoffstetter, 1986). During glacial retreat, large lakes formed on the Altiplano (see Stoertz & Ericksen, 1974; Lavenu et al., 1984) and three of these have been named: Lake Bnllivifíii was n southern expansion of Lake Titicaca (which presently covers 8,400 km’) in the northern Altiplano and covered an area of 12,600 km’; Lake Minchín and Lake Tauca occupied the same area in the central and southern Altiplano, including present- day Lake PoopÓ, Salar de Coipasa and. Salar de Uyuni, and had maximum extensions respectively at - 30,000 yrbp and 13,000- 11,OOO yrbp (Servant & Fontes, 1978). Two lake levels called Lake Cabana and Lake Mataro, which occurred prior to the Sorata glaciation, have also been identified (Lavenu et al., 1984). Campbell ef al. (1985) have suggested that glacial lakes which formed during the last glacial advance may have been united to form one large lake which Campbell (1989) named Lake Carrasco, that covered an excess of 150,000 km2, or nearly all of the surface area of the

Bolivian Altiplano. During times of glacial retreat, as today, these lakes contracted or disappeared. The overall result is that the climates on the Altiplano were greatly altered during times of glacial advance and retreat.

Climates to the east of the Cordillera Oriental were likewise effected by glacial advances and retreats. The tropical and subtropical lowlands of eastern Bolivia experienced cold-dry climates during glacial advance, resulting in contraction of tropical forest biomes and expansion of savanna biomes. During times of glacial retreat, as today, these areas had warm-wet climates with extensive tropical forest biomes and restricted savanna biomes (Arroyo el al., 1988). These climatic changes affected the distribution of animals living in these habitats, and the fauna which occurs at any one locality during times of glacial advance may be different from that which occurs in the same locality during times of glacial retreat. Unfortunately, the chronology of glacial advances and retreats is not well documented in Bolivia, and the identity of glacial faunas versus interglacial faunas has yet to be firmly established. Nevertheless, this feature must be kept in mind when attempting to explain differences in taxonomic composition of mammal faunas, as they may be due to differences in ecology, altitude, and/or time.

3. Tlie Great American Faunal Interchange. Prior to about 2.5 Ma, North and South America were separated by a narrow seaway called the Bolívar Trough which connected the Caribbean and Pacific Oceans across what is today northwestem Colombia and southern Panama. About 2.5 Ma this seaway began to disappear as a result of tectonic uplift of southem central America and/or a glacioeustatic drop in sea level (Webb & Barnosky, 1989; Keller et al., 1989). The Panamanian Land Bridge came progressively into existence, uniting North and South America. The Pacific-Caribbean marine gateway finally closed by 1.8 Ma (Keller et al., 1989). The land connection permitted the reciprocal intermingling of the long-isolated biotas’of these continents, an event of spectacular importance known as the Great American Faunal Interchange (Marshall, 1988).

The land mammals which walked across the newly emergent land bridge froth North to South America included members of the Tayassuidae and Mustelidae which are first known from rocks of Chapadmalalan age in Argentina (Marshall, 1985). However, it is in rocks of Uquian through Lujanian age that we begin to see in South America a major contingent of these North American immigrants which include: Proboscidea (Gomphotheriidae), Lagomorpha (Leporidae), Carnivora (some Procyonidae, more Mustelidae, Canidae, Felidae, Ursidae), Perissodactyla (Equidae, Tapiridae), Artiodactyla (more Tayassuidae, Camelidae, Cervidae) and eventually man (Homo sapiens) about 12 ka (Marshall, 1985,1988; Marshall ef al., 1984). The appearance of these taxa in South America is thus an important immigrant datum event for recognizing faunas of Uquian through Lujanian age.

4. Megafaunal Exfinciions. The end of Pleistocene time in Bolivia, as elsewhere in South America, is marked by the extinction of most large body size mammals. The vast majority of these now extinct mammals had body weights in excess of 100 kg, and because of their large size are commonly referred to as megafauna. The peak of these extinctions occur between 12-10 ka (Marshall et al., 1984). In Bolivian faunas these now extinct megafauna include all members of the families Glyptodontidae, Megatheriidae, Mylodontidae, Megalonychidae, Macraucheniidae, Gomphotheriidae and Equidae; and some Dasypodidae (Pampafherium), Camelidae (Palaeolama),

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Cervidae {Morenelaplius) and Felidae {Sniilodon). As demonstrated at Ñuapua, these extinctions occurred prior to 7200 k 400 yrbp as indicated by the oldest carbon-14 date on the Ñuapua 2 fauna which includes only extant taxa. The exact cause of these extinctions is unknown, although they have been attributed to excessive hunting (overkill) by early man, climatic change (a sharp climatic drying occurred in Bolivia and adjacent regions starting at -10,000 - 9,000 yrbp in the Andes and - 8000 yrbp in the lowlands; Servant et al., 1989b; Absy et al., 1991; M. Servant, personal communication), and a combination of the two (Hoffstetter, 1986).

ACKNOWLEDGMENTS

Aspects of this study were supported by grants from the National Geographic Socicly (2467-82, 2908-84, 3381-86); the Gordon Barbour Fund, Department of Geological and Geophysical Sciences, Princeton University; and the National Science Foundation (EAR- 8804423). Stratigraphic work was funded by the Institut Français de Recherche Scientifique pour le Développement en Coopération (Orstom) and realized in collaboration with field geologists of Yacimientos Petrolíferos Fiscales Bolivianos (YPFB). For help on the geology and/or identification of specimens we thank D. Anaya, A. Berta, R. Céspedes, M. Gayet, A. Lavenu, R. Hoffstetter, R. Marocco, J. Oller, J. Pacheco, R. Pascual, G. Sanjinés, R. Suirez & C. Villarroel.

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FOSILES Y FACIES DE BOLIVIA - VOL. I VERTEBRADOS . CARRASCO, C. P. 1986. Notas preliminares sobre la geologia del extremo noroccidental del Departamento de Pando. VI1 Congreso Geológico de Bol

the eocene to pleistocene vertebrates of bolivia and their...

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