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Palaeogeography, Palaeoclimatology, Palaeoecology 165 (2001) 126www.elsevier.nl/locate/palaeo

Vertebrate taphonomy in circum-lake environments:three cases in the Guadix-Baza Basin (Granada, Spain)

Mara T. Alberdi a,*, Mara A. Alonso b, Beatriz Azanza a,c, Manuel Hoyos ,b,Jorge Morales a

a Departamento de Paleobiologa, Museo Nacional de Ciencias Naturales, CSIC, Jose Gutierrez Abascal, 2. 28006 Madrid, Spain

b Departamento de Geologa, Museo Nacional de Ciencias Naturales, CSIC, Jose Gutierrez Abascal, 2. 28006 Madrid, Spain

c Departamento de Ciencias de la Tierra (Paleontolog a), Universidad de Zaragoza, 50009 Zaragoza, Spain

Received 10 August 1999; accepted for publication 26 May 2000

Abstract

This work analyses the origin and taphonomy of three Plio-Pleistocene mammal assemblages from the Guadix-

Baza basin (Granada, Spain) : Huelago; Huescar-1; and Cullar de Baza-1. Similarities and differences in the taphonomic

features are evaluated with regard to marginal lacustrine sedimentary processes involved in the accumulation of these

mammal assemblages. Selective preservation of skeletal-part and taxa in relation to facies have been explored to

determine their suitability for palaeoecological analysis. The mortality in Cullar de Baza-1 and Huelago-1 corresponds

to a catastrophic pattern, but other taphonomic features of the bones indicate that accumulation processes were

diachronic as occurred in Huescar-1. This could be explained by selective-predation and/or seasonal accumulation of

bones. Hydraulic sorting and transportation greatly controlled the size and shape of accumulated skeletal elements,

and the different preservational circumstances of each environment largely constrained the taxonomic composition of

the fossil bone assemblages. Autochthonous fauna only occurs in Huescar-1 corresponding to subaquatic environments.

The absence of carnivores among the identifiable remains from Huelago-1 has no plausible taphonomic or

sedimentological explanation. Nevertheless, after taking into account the taphonomic factors, the differences in

taxonomic composition between these three mammal assemblages reflect differences in the surrounding habitats. The

great diversity of ruminant artiodactyls, in particular browsers, is indicative of wooded or bushy areas in the

surroundings of Huelago-1 although not in the immediate area of the lake margin. This diversity coincides with that

observed in other Villafranchian localities and represents the greatest diversity of artiodactyls known from the

Neogene and Quaternary record of Western Europe. In turn, the high diversity of sub-aquatic forms and a smaller

variety of artiodactyl species in Huescar-1, reflects an open, sparsely forested environment susceptible to seasonal

drought. A similar sparse forested environment has been deduced for Cu llar de Baza-1. The climate and environmental

conditions in Huescar-1 and Cullar de Baza-1 are consistent with a climatic deterioration at the beginning of the

Middle Pleistocene (Glacial Pleistocene). 2001 Elsevier Science B.V. All rights reserved.

Keywords: Guadix-Baza basin; mammals; paleoenvironments; Plio-Pleistocene sediments; southeast Spain; taphonomy

* Corresponding author. Fax: +34-9-5644740.

E-mail address: [email protected] (M.T. Alberdi)

Recently deceased.

0031-0182/01/$ - see front matter 2001 Elsevier Science B.V. All rights reserved.

PII: S 0 0 3 1 - 0 1 8 2 ( 0 0 ) 0 0 1 5 1 - 6

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2 M.T. Alberdi et al. /Palaeogeography, Palaeoclimatology, Palaeoecology 165 (2001) 126

1. Introduction favoured the formation and preservation of abun-

dant remains of macro- and micro-vertebrates. A

relative abundance of bones that allows methodicalThe formation of attritional vertebrate tapho-

cenoses strongly depends on sedimentary processes excavation is preserved in only four of these depos-

its: Huelago (Pliocene/Pleistocene boundary,and depositional environments, which control the

accumulation, burial and preservation of bones. Middle Villafranchian, MN 16b); Venta Micena(Lower Pleistocene, latest Villafranchian);Sedimentary processes strongly influence relevant

data for palaeoecological interpretation such as Huescar-1 (early Middle Pleistocene, Galerian);

and Cullar de Baza-1 (Middle Pleistocene,the anatomic and taxonomic composition of fossil

assemblages. Therefore, palaeoecological studies Galerian) (Alberdi et al., 1989b). From these, only

the deposit of Venta Micena is not considered inrequire good sedimentological control. In this

study, we analyse the taphonomic and sedimentary this work because detailed taphonomic studies

(Palmqvist et al., 1996 and Arribas and Palmqvist,processes involved in the formation of three Plio-

Pleistocene macromammal assemblages in the 1998) show that the bones accumulated exclusively

by biotic factors (mainly hyaenid activity). AllGuadix-Baza basin (southeastern of Spain). This

allowed us to evaluate the suitability of taxonomi- these deposits belong to the depositional sequence

VI of Fernandez et al. (1996b). Detailed datacal data from these assemblages for further palaeo-synecological studies, in order to minimize biases about the sedimentology of the deposits, and the

taxonomy and palaeoecology of the collectedin important parameters such as diversity esti-

mates. In particular, we are concerned here about fauna, can be found in Alberdi and Bonadonna

(1989) and Alonso (1991).determining to what point the differences in the

taxonomic composition reflect: selective mortality; The Plio-Pleistocene assemblages of large mam-

mals in the Guadix-Baza basin were preserved inthe preferential record of taxa with a particular

habitat preference; or differences in the surround- lake-margin settings. Lake margins were pointed

out as a preservational context for vertebrates ining habitat.

The Guadix-Baza basin is located in the south- lacustrine environments, though they were not

finally included in the 34 taphonomic modes sum-eastern part of the Iberian Peninsula within the

Betic Ranges (Fig. 1). This basin has an overall marised by Behrensmeyer and Hook (1992).However, they provide important sites for thearea of ca. 4400 km2 and an average altitude of

1000 m above sea level (Alonso, 1989). This basin preservation of vertebrate fossil assemblages in the

Spanish Neogene basins, more common than flu-was part of a post-orogenic intra-montane system,

that formed during the Upper Miocene. At this vial channel and floodplain contexts (Lopez

Martnez et al., 1987; Calvo et al., 1993). Moderntime, the last important movements that formed

the Betic Ranges, the so-called post-Serravallian lake margins are areas where many different mam-

mals concentrate: terrestrial animals go there tocompressive phase, took place. Later tectonic

movements, which have continued until present graze, browse, drink and hunt as well as mate,

interacting with the autochthonous aquatic andtimes, are considered neotectonic (Sanz de

Galdeano, 1983; Fernandez et al., 1996a). semi-aquatic animals. However, the peculiarities

of certain sub-environments can substantiallyShallow marine sedimentation persisted in the

Guadix-Baza basin until the Upper Tortonian in change the anatomic and taxonomic compositionof the bone remains which are incorporated in thethe west and the Lower Pliocene in the east. Later,

this changed to endorheic terrestrial conditions. corresponding deposits as taphocenoses. This

paper contributes to the knowledge of the preserva-High subsidence rates promoted centripetal and

asymmetric sedimentation during the Middle/ tional patterns for attritional vertebrate assem-

blages in lake margins.Upper Pliocene and the Pleistocene, consisting of

marginal alluvial fan systems that graded to pal- Studies of the taphonomic processes were con-

ducted during methodical excavation of the threeustrinelacustrine environments in the most

depressed axial parts of the basin. This pattern fossil assemblages. These included detailed analysis

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3M.T. Alberdi et al. /Palaeogeography, Palaeoclimatology, Palaeoecology 165 (2001) 126

Fig. 1. Geographic situation and microstratigraphy of the three localities studied in the Guadix Baza basin (Granada, Spain). 1,Conglomerates and sands; 2, sands; 3, sandy silts; 4, silts; 5, calcareous silt; 6, clays; 7, marls; 8, marly silt; 9, limestone; 10, root

bioturbation; 11, organic matter; 12, vegetal fragments; 13, gastropods; 14, ostracods; 15, preferential levels for the accumulation of

bones; 16, calcareous concretions; 17, carbonaceous lenses; 18, gypsum lenses; 19, gypsum concretions; 20, erosion surfaces; 21,

channels; 22, iron-oxide levels.

of the spatial distributions and taphonomic fea- study we emphasize the taphonomic similarities

and differences of the three deposits and discusstures of the bone remains and the sedimentology

of the deposits in which they are contained. In this them in detail.

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PLATE I

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2. Methodology only three out of the five bone weathering stages

distinguished by Behrensmeyer (1978):

1. bones with smooth surfaces, with superficialLocal stratigraphic sections of the three locali-

ties studied were measured and correlated with the fissures which do not create irregularities

(similar to stage 1);litho-stratigraphic units defined for the basin

(Alonso, 1991). The stratigraphy, sedimentology 2. average fissuring, slight scaling, with parts ofthe bone surface missing (similar to stageand lateral facies relationships were studied for

each deposit. Sediment and bone samples were 2); and

3. very irregular surface because of deep fissur-also collected for laboratory studies that included

conventional petrography in thin section, X-ray ing, though there may be outcropping on

large parts of the surface of the internaldiffraction and X-ray fluorescence.

The three deposits were methodically excavated, layers (similar to stages 3+4).$ Alterations caused by physical and chemicalusing grids (see maps of excavated areas in Alberdi

et al., 1989a, Figs. 2, 4, 5, 6 and 7). Table 1 shows agents (corrosion, crusts) previous to, or vir-

tually contemporary with, the burial.a summary of the data obtained from the excav-

ations. The following variables were observed for $ Skeletal-element. As the skeletal representations

may vary with the modifications introduced byeach bone sample recovered:$ Lithostratigraphic level. diverse biological (Brain, 1981; Shipman,

1981a) or physical ( Voorhies, 1969; Hanson,$ Spatial position on the grid ( X, Y, Z ).$ Dimensions (length, width, height). 1980) accumulating agents, the following cate-

gories of elements are recognised:$ Orientation and degree of dip of the long axis.$ Alterations caused by biological agents: marks 1. unidentifiable splinters;

2. isolated teeth;and breakages caused by teeth [Plate I( D2)],

fractures produced by trampling and root bioer- 3. cranial appendages;

4. Groups I (vertebrae and phalanges), II ( longosion [Plate I(C )] penecontemporaneous with

the deposit or by superficial burial. bones) and III (skulls and mandibles/jaws)

of the hydraulic behaviour categories pro-$ Alterations caused by physical agents: abrasion

or breakages caused by blows, more frequent posed by Voorhies (1969); and5. coprolites [ Plate I(D1)].during transport by traction along the river bed

[Plate I( B)], and weathering [Plate I( A)]. The Voorhies groups of bones require different min-

imum fluid shear stress to initiate transport. Thus,nature of the fossil material permitted using

PLATE I

(A) Weathering stages.

1 Stage 1: tibia diaphysis ofEquus from Huescar-1 ( HU1-A466) showing a smooth fresh surface texture (3.26).

2 Stage 1: MtIV ofEquus from Cullar de Baza-1 (CU1-B45) showing initial cracking parallel to bone fibre structures (1.92).

3 Stage 2: bone splinter from Huescar-1 (HU1-A596) showing deep cracking with angular crack edges in cross section (1.44).4 Stage 3: bone splinter from Cullar de Baza-1 (CU1-sn) showing a wide patch of weathered bone of rough texture. Deep

cracking and flaking with the external layered bone removed (1.83).

(B) Abrasion marks.

1 Abraded bone splinter showing marks of the impact of pebbles and cobbles from Huescar-1 (HU1-A1069) (2.11).

2 Abraded bone splinters of elephant tusk showing scratches by drag from Huescar-1 (HU1-A740) (1.2).

(C ) Plant root marks on a bone splinter from Huelago-1 ( HC1-D29) (1.34).

(D) Signals of predators.

1 Section of a coprolite from Huelago-1 (HC1-sn) (1.24).

2 Bone splinter showing possible gnawing marks (crenulated edge) from Huelago-1 (HC1-A106) (1.6).

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Table 1

Measured and calculated values for taphonomic variables in the excavated bone assemblages from the Plio-Pleistocene Guadix-Baza

basin (Granada, Spain)a

Huelago-1 Huelago-D Huescar-1 Cullar de Baza-1

S (m2) 46 12 28 28D (m) 3 3 4 1.5

V (m3) 138 36 112 42

TNSP 620 67 1260 326

NISP 172 11 260 132

NNISP 448 56 1000 194

NISP/NNISP 2.79 5.09 4.84 1.469

Density 4.49 1.86 11.25 7.76

NISP (m3) 1.24 0.3 2.32 3.14

NNISP (m3) 3.24 1.55 8.94 4.6

Macromammal diversity 11 3 11 10

Micromammal diversity 11 0 11 9

Other vertebrate diversity 2 0 16 7

a S, Surface; D, depth; V, volume; TNSP, total number of specimens; NISP, number of identified specimens; NNISP, number of

unidentified specimens; density, average NISP per m3; richness, number of taxa identified

Group I includes bones which are immediately lysed. In order to make a comparison between the

taxonomic composition of the different deposits,transported by flotation or by saltation; Group II

includes those transported later and usually by Spearmans coefficient of rank order correlation

was computed as a non-parametric measure oftraction; while bones of Group III are the most

difficult to transport. Consequently, their propor- similarity and the unweighted pair-group method

using arithmetic averages (UPGMA) was the clus-tions in fossil assemblages indicate sorting pro-

cesses related to hydraulic entrainment and tering technique.

Age profiles were constructed only for the moretransport (Behrensmeyer, 1975a,b). Bone elementcategories 1, 2, 3 and 5 were not considered in abundant fossil taxa (Equus livenzovensis in

Huelago, and E. altidens in Huescar-1 and CullarVoorhies experiments, but 1 and 2 include the

largest percentage of the collected remains for de Baza-1). Aging was estimated from the degree

of wear on cheek teeth (Hulbert, 1982; Kurten,which the fracturing indices of the levels excavated

were measured and compared; category 3 should 1983). Five classes were established, the first one

comprises deciduous teeth and the rest correspondnot be included in Group III, while 5 is not a

skeletal element. to the four stages of crown height proposed by

Eisenmann et al. (1988) for the permanent cheekThe data thus obtained (Alonso, 1991) were

encoded for statistical treatment using and teeth. The five classes are more or less equivalent

to the ontogenetic stages: immature; young mature;commercial (S and ) pro-

grammes. Bi-dimensional and three-dimensional adult; aged; and senile.

Body size spectra were estimated for theprojection graphs were constructed exploring vari-ous possibilities using a selection of the remains mammal species. The size categories are based on

body weight following Andrews et al. (1979),according to the category variables. Rose diagrams

were constructed to explore the orientation of the Andrews (1990a, 1992a,b), Andrews and Alpagut

(1990), though a separate category for megaherbi-long bones. The average bone size was statistically

compared between the levels using x2 test. vores (Owen-Smith, 1988) was considered. Body

weight of fossil species was predicted from lowerContingency tables were computed for the cate-

gory variables (stratigraphic level, skeletal element, molar lengths (Legendre, 1986; Janis, 1990) or

long bone lengths (Gingerich, 1990; Scott, 1990).weathering and marks) and their relationship ana-

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3. Sedimentary and palaeogeographic setting palustrine sediments. Each flooding event started

with an erosional surface followed by mud pebbleThe three deposits studied in this work can be conglomeratic sands and ended with silt and clay

included in the Group D, that is, Inland basins and carbonate beds with incipient pedogenic fea-and traps, of the classification of fossiliferous tures that reflect periods of drying after the floodpaleoenvironments in continental regimes by events. The scarcity of bedforms in the mud pebbleBishop (1980). In view of the sedimentary features sands that fill the channels, suggest that the streamsdisplayed by these deposits they can be included were strong enough to partially erode the superfi-in subgroup 7: Lacustrine, fluvio-lacustrine, cial sediments and incorporate them in the formswamp, and spring-eye margins, as defined by the of clasts to the channel sediments. Besidessame author. The Huelago deposit is broadly intraclasts, the streams crossing the swampy areainterpreted as accumulated in a swampy environ- carried bone and mollusc fragments and depositedment with episodic fluvial influence. The Huescar-1 them on the input deltas of the rivers.deposit was accumulated in fluvial environments The sedimentation in Huelago was predomi-which were periodically covered by lacustrine nantly detrital, the chemical precipitation of car-deposits. The Cullar de Baza-1 deposit could be bonate having been a subordinate process. Several

classified in the swampy and lacustrine subgroup. structures in the fine-grained sediments, recognisedThus the three studied deposits correspond to both in the outcrop and in thin sections, can bemixed cases that are not specifically considered in attributed to incipient pedogenic processes. Thesethe Bishops classification.

structures comprise abundant root traces, perfora-The stratigraphic logs obtained from these

tions, quartz grains corroded by the micriticdeposits are shown in Fig. 1. A detailed description

groundmass, argillans and ochre-coloured patchesof the deposits has been made in Alonso (1991).

at several scales, fissures caused by drying andFig. 2 shows block diagrams reconstructing the

structures due to prismatic shrinkage (cf. Estebanenvironments in which the deposits were formed.

and Klappa, 1983). Similar features have been

interpreted as resulting from pedogenic processes3.1. Huelago-1 (A+B+C) and Huelago -D

in swampy areas (Alonso et al., 1988).

Fluctuation of the phreatic groundwater levelAlonso (1991) interpreted this deposit as havingis evidenced by the accumulation of patches of

accumulated in a swampy mud flat that fringed airon oxides distributed at several levels in a samelarge lake. The sediments consist of green and greylithologic horizon. Migration and further concen-silts containing gastropod shells, charcoaltration of iron oxides is a common mechanism forintraclasts and cyanobacterial oncoids, superim-the formation of iron precipitates in the vadoseposed with a dense framework of millimetre-thickzone (Margalef, 1983).root traces. The swamp was largely colonized by

The rather sparse occurrence of gypsum in someherbaceous vegetation, evidenced by these abun-beds of the Huelago deposit cannot be considereddant root traces. Vertical oscillations of the phre-as an indicator of strong evaporitic conditions. Onatic zone, probably forced by seasonal climaticthe one hand, veins of fibrous gypsum fillingvariations, gave rise to iron oxide precipitates

fissures in fine-grained detrital sediments must beduring the humid periods and to the precipitationinterpreted as early diagenetic. On the other hand,of lenticular gypsum and some carbonate duringlocal occurrences of aggregates of lenticularthe dry periods.gypsum can be explained by the precipitation ofThere is evidence of episodic fluvial influence insulphate around roots and/or tubeworm burrowsthe northern side of the swamp: four flood events(Cody, 1979). Further proofs of non-saline,are recognized within the Huelago-D sectionswampy environments or lacustrine coastal settings(Fig. 1) and at least one flood event in Huelago-1.are the stenohaline mollusc fauna found in theThese events are recorded by the occurrence of

muddy sand-filled channel bodies interbedded with deposit, such as Ancylus fluviatilis, and the absence

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Fig. 2. Reconstruction of the Huelago, Huescar-1 and Cullar de Baza-1 environments and composition of the corresponding vertebrate

assemblages. The first column of graphs represents the percentages of identified specimens corresponding to different skeletal-elements

categories (Groups I, II and III, after Voorhies, 1969). The second represents the percentages of species per size interval. The third

represents the percentages of specimens per taxonomic group. The fourth represents the number of species per taxonomic group. The

data used to build the skeletal-parts and size spectra was compiled only from the material collected in excavation. Section legend as

in Fig. 1 and abbreviations as in Table 1.

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Fig. 2. (continued).

of species that tolerate higher salinities (Robles, 3.2. Huescar-1

1989).With regard to the palaeogeography of The sediments observed in this place (Fig. 1)

were related to an outlet where alluvial streamsHuelago, the swampy area was located between

the northern margin of the Guadix-Baza basin and flowed into a lake. White calcareous silt beds of

this section accumulated in a well-oxygenated shal-a large lake. Palaeocurrent directions measured in

the channel bodies interbedded with the palustrine low lacustrine environment as evidenced by the

pale (white and yellow) carbonates, devoid ofsediments indicate that the source area was located

towards W-SW, in the calcareous rocks that fringe organic matter and lamination. The aquatic bird

fauna (Sanchez Marco, 1989) suggests ecologicalthe basin in that area (Alonso, 1991).

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conditions well fitting the sedimentological inter- overlying the silts display features, such as clay-

rich carbonaceous lenses (C and C beds in Fig. 1) ,pretation, since most of the species are characteris-

tic of densely vegetated lake margins. Numerous indicative of swampy conditions and containing

abundant gastropod shells and bone remains. Apalaeophreatic levels, evidenced by the several

levels of accumulation of iron oxides in a same small body of sandy silts, interbedded within hori-

zon D1, is interpreted as deposited by ephemeral,lithologic horizon, are indicative of an oscillating

water-table. low-energy streams entering the palustrine environ-

ment. The upper surface of the horizons D1C isThe detrital beds grade towards the east into a

3 m thick bed which also contains bone remains. very irregular showing small-scale flame structures

most likely caused by liquefaction induced byThis bed is formed of stacked lens-like bodies of

gravelly sands with individual thickness ranging seismic shock, related to the tectonic instability of

the basin.0.71 m. Planar cross-stratification occurs occa-

sionally at both the fronts and sides of the single The transition from sandy silts or clay-rich

carbonaceous beds to marls and limestones, asdetrital bodies. These bodies are interpreted as

alluvial bars whose tops were affected by incipient represented by horizons D1C to D ( Fig. 1), repre-

sents a change towards lacustrine conditions,pedogenic processes as evidenced by centimetre-

thick silty sands with rhizoliths. The source area reflecting an increase of lake water depth. This issupported by the progressive disappearance of rootof the channels was located to the east in the area

of the Botardo hill as evidenced by the clast traces and the development of carbonate beds.

Episodic lowering of the lake water level, markedlithologies which include carbonates, flint frag-

ments and Compostela hyacinths (Alonso, 1991). by local accumulations of organic-rich marls,

favour colonization of the lake by aquatic vegeta-

tion, as proposed by Wenninger and McAndrews3.3. Cullar de Baza-1

(1989). Horizons D and D2

(Fig. 1) record a lake

water rise and further expansion of the lacustrineIn this deposit, the fossil remains occur mainly

in palustrine to shallow lacustrine carbonates and environment. The limestone lenses D2

and D2 ,

interbedded within horizon D, shows a greatmarlstones. Towards the east, these beds interfinger

with the alluvial sediments of the Conglomerate amount of calcified algal remains. Silt and lignitebeds containing abundant vertebrate remainsand Red Sand Formation and westwards they pass

laterally into the Carbonate Formation (Alonso, (horizons D1 and C) overlying the carbonates

indicate subsequent lowering of lake water levels.1991). The terrigenous sediments interbedded with

carbonates and marls of the Cullar de Baza-1 The uppermost beds of the Cullar de Baza-1

deposit (horizons FH in Fig. 1) consist of roughlydeposit show E W palaeocurrent directions, coin-

cident with those determined in the Conglomerate laminated fine-grained sands, silts and clays which

are barren of vertebrate fossils. They are interpre-and Red Sand Formation (Alonso, 1991).

The Cullar de Baza-1 deposit is formed by four ted as accumulated in a well-oxygenated open lake

environment, during a phase of expansion of themain lithofacies (Fig. 1) representative of the

transition from alluvial to shallow lacustrine envi- lake system towards E (Alonso, 1991). In the

Cullar de Baza-1 deposit, these beds are cappedronments in the area. Palustrinelacustrine deposi-

tional conditions, characteristic of the Upper by a thin package of shallow lacustrine limestonebeds (not represented in Fig. 1) that are in turnCarbonate Formation (Alonso, 1991), were estab-

lished in the area after the sedimentation of the overlain by alluvial sediments with pedogenic fea-

tures, representing the end of lacustrine sedimenta-Conglomerate and Red Sand Formation. The

transition between the alluvial and lacustrine for- tion (Alonso, 1991).

Neither the sedimentary features of the lakemations is rapid but gradational (horizon B in

Fig. 1) . Abundant root casts within the silts and sediments nor the palaeoecological inferences from

the fauna included in the deposit indicate highthe dark colour of this facies suggest a progressive

swamp formation over the area. Calcareous beds salinities although locally ostracods may indicate

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Table 2moderate salinities (Civis, 1989). Scattered gypsumFrequencies (%) in selected anatomical categories of the threeblades and pseudomorphs of gypsum crystalsPlio-Pleistocene localities in the Guadix-Baza basin (Granada,

within the carbonates might be an indication ofSpain); groups I, II and III, after Voorhies (1969)

low to moderate salinity, but similar features haveHuelago-1 Huescar-1 Cullar de Baza-1been interpreted as resulting from plant decay

(Cody, 1979). Gastropods found in the lacustrineAppendages 2.25 0.23 2.14

sediments belong either to hygrophilic speciesTeeth 28.87 19.76 23.92

(Vallonia enniensis), which are characteristic of Group III 1.49 0.79 5.71Group II 7.13 2.54 6.34marginal lake environments, or species whichGroup I 5.8 6.13 4.76inhabit open herbaceous biotopes (Pupilla musc-Fragments 54.35 70.49 56.44orum, Truncatellina cylindrica, Vallonia pulchella),Coprolites 0.64 0.07 1.22

showing a great tolerance to variations in both

humidity and temperature (Robles, 1989). The

fish species determined in this site (Doadrio and the absence of carnivores among the identifiedCasado, 1989) are characteristic of low salinities, remains is unusual. Coprolites [Plate I(D1)] occuralthough they can live in a wide range of temper- in the marly silt beds; they contain bone remains

atures and oxygen levels. and their phosphate content is high (12.5%).

Table 34. Taphonomic study of fossil bone accumulations Vertebrate species diversity of the three Plio-Pleistocene locali-

ties in the Guadix-Baza basin (Granada, Spain), after Alberdi

et al. (1989b)This study included a statistical analysis of the

anatomic and taxonomic compositions, size distri-Huelago Huescar-1 Cullar de Baza-1

bution, state of preservation and spatial distribu-Piscestion and orientation of fossil bones at the threeLeuciscus Leuciscus pyrenaicus Leuciscus pyrenaicuslocalities. These data are then used to interpret thepyrenaicus

mechanisms of bone accumulation and burial.Reptilia

Acanthodactylus cf.4.1. Huelago depositerythurus

Lacerta cf. lepidaThe results given below correspond to Lacerta (Podarcis) cf.

Chalcides cf. bedriagraiHuelago-1 (grids A, B and C ). The lower levelBlanus cinereus(Huelago-D) has not been analysed in detail

Testudo sp. I Emydidae indet. Testudo sp. IIalthough its characteristics are similar. However,Avesits anatomic and taxonomic compositions are

cf. Tachybaptus ruficolisincluded in Tables 1, 3 and 4.Anas crecca/

The anatomic composition shows an equilib-A.querquedula

rium between the identified and unidentified bone Anas platyrhynchosremains (Table 2 and Fig. 2). There is a remark- Anas clypeata

Anas streperaable abundance of isolated teeth; most belong toAnas sp.Equus which is by far the most abundant largeNetta rufina

mammal. The species under 1 kg body weight areAythya ferina

the most common (>35% of the total), the interval Aythya nyrocabetween 180 and 1000 kg is also well represented Aythya fuligula

Aythya sp.mainly by ungulate species. The mammal diversityPerdix perdixfound in Huelago is comparable to the knownCrex crex

range for the Spanish Tertiary, though it is especi-Bubo bubo

ally high in ruminants (eight species). However,

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Fig. 3. Horizontal distribution of bones from Huelago-1 at different stratigraphic levels.

observed in marly silt beds, that is, a bone was coincides with the base of the litho-stratigraphic

Level 4 (Fig. 1), while the others do not coincidefragmented into three parts, the central part beingmore deeply sunk and the others dipping in oppo- with lithological changes.

The orientation of the bones in the lowermostsite directions.

The spatial distribution of the bones is not layers ranges over the excavated surface from

directions between 0 and 90 (with a maximumuniform but there is no linear bonebed type con-

centration attributable to palaeo-channels ( Fig. 3) . between 10 and 40) in grid A, and between 60

and 180 (with a maximum between 70 and 110)There are some areas of high bone density on

vertical cross-sections through the beds ( Fig. 4). in grid C (Fig. 4). Similar orientations are main-

tained in the stratigraphically higher levels with aThe most evident bone concentration in Huelago-1

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deepest levels well below the area influenced by

the present soils.$ Skeletal-elements: jaws and cranial appendages

appear to be preferentially associated with the

upper beds of calcareous silts. The teeth,

although present in all levels, are primarilyassociated with the lower strata. However, the

results of a x2 test should be taken with caution,

as the expected minimum values were very low.$ Weathering: root marks associated with the

highly weathered remains were only observed

on grid B. 40% of the bone splinters in grids A

and C are more intensely weathered than the

other skeletal elements. The degree of weather-

ing was usually low (stage 1) in teeth.

4.2. Huescar-1 deposit

The composition of the various skeletal ele-

ments (Table 2 and Fig. 2) shows a notable predo-

minance of unidentified bone remains (70%). As

in Huelago, most of the identified remains corre-

spond to isolated teeth belonging to Equus, the

most abundantly represented genus. The pattern

of size spectrum is also similar to that in Huelago

though the interval between 45 and 180 kg body

weight is poorly represented. The presence ofhippopotamus and the high diversity of water birds

is noteworthy.

Around 54% of the bones show marks of abra-Fig. 4. Vertical distribution of bones from Huelago-1 and rose

sion or breakages caused during transport bydiagrams showing orientation of bones at different levels (n,traction. Of these, 11% have small grooves ornumber of long axis bones included in the rose diagram).incisions which are very superficial. The greater

part of the surface of the remaining 43% is fur-

rowed by deep and shallow abrasion marks ofmaximum between 10 and 40 on grids A and B

but no preferential orientations were found on impact and edges or projecting parts rounded or

polished from traction. There are some patternsgrid C. There is a similar tendency in the superficial

levels with a very clear maximum 50 and 70 on of clasts produced by pressure; in some cases the

clast is still in place. No marks of carnivores orgrids A and B, and a bi-modal orientation wasobserved for grid C with another peak between scavengers were observed on the surface of the

remains, although these may have been masked or130 and 160 (Fig. 4).

There are no differences in the average size of erased by abrasion. Only 8.7% of the remains

showed bioerosion. Except in the odd case wherethe bone remains with depth. On comparison of

variables: patches of eroded bone appeared to be caused by

lichens or algal filaments (included in the calcare-$ Bioerosion: only one significant relationship was

encountered on grid C indicating that the root ous crusts on the bones) the majority are shallow

grooves [Plate I(C)] produced by dissolutionmarks are preferentially accumulated at the

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induced by the roots of herbaceous vegetation (see lation in grid B corresponding to the bones in

Levels 3 and 4 (Fig. 5).Shipman, 1981b; Cook, 1986; Lyman, 1994).

Huescar-1 bones are scarcely weathered, 36% In vertical sections of the outcrop the great

majority of bones on grid A are concentrated inshowed stage 1 [Plate I(A1)] and only 9% stages

2 or 3 [Plate I(A3)]. the detrital beds of Level 2 (90%) and Level 4

(9.5%), while the rest (0.5%) occur in the calcare-The bones are densely concentrated and uni-formally distributed over the entire surface of grid ous beds (Alonso, 1991). The concentration of

bones in Level 2 forms a pocket with a very evidentA at the different intervals of depth (Alberdi et al.,

1989a). In contrast, there are two areas of accumu- dip to the west, becoming thinner in this direction,

Fig. 5. Horizontal and vertical distributions of bones from Hue scar-1 and rose diagrams showing orientation of bones at different

stratigraphic levels (n=the number of long axis bones included in the rose diagram).

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while in Level 4 it is situated in a horizontal bed Baza-1 is slightly lower than that of Huelago orHuescar-1, however, the reptile diversity is high(Fig. 5). On Grid B, the bones in detrital beds of(six species).Level 4 exhibit a preferential horizontal distribu-

No abraded remains, fractures, incisions, ortion, while the bones in calcareous beds of Levelabrasions were recognised, although a small frag-3 are more dispersed.

ment had very noticeable smooth surfaces whichAlthough the bones appear orientated in allcould have originated through the action of cur-directions on grid A with a general predominancerents of water with mud. The actions of predatorsof those associated with the first quadrant (090and scavengers were unequivocally identified inE), there is a slight preference to NS orientationsome remains, mainly splinters. These consist of(020 E). NS and 5070 E directions seem toround depressions or perforations on the bonebe the preferential orientations on grid B, wheresurface, which are usually small (510 mm).there are only measurements of long bones onSimilar marks are produced by carnivore teethLevel 3 (Fig. 5).(Hill, 1980). There are also fractured edges in aDue to the scarcity of remains in the calcareouscrenulated form similar to that caused by gnawingsilt and marly beds of Levels 1 and 3 on grid A,(Brain, 1981). This activity would also be responsi-the contingency tables could be applied only to

ble for part of the greenbone fractures with sur-Levels 2 and 4. The abundant splinters of elephant faces oblique to the long axis of the bone splintertusk were separated into a new category in the(cf. Behrensmeyer and Hill, 1980). A quarter ofskeletal-elements. On grid A there is no differencethe bones showed millimetric marks of a frame-

between the average size of the remains by levels.work of small roots.

However, a difference does exist on grid B, proba-Only 12% of the remains are in an advanced

bly due to the elephant remains, as the craniumstage of weathering [Plate I(A4)] and 68%

and the ribs which have a very different size fromhave practically no indication of weathering

the rest, raises the average size for Level 3.[Plate I(A2)].

$ Bioerosion: on grid A there is a greater propor-Articulated elements were occasionally found in

tion of bones with root marks in Level 4, thisall the levels. No spatial distribution patterns can

is still very small, a total of 8%.be observed (Fig. 6). However, a greater concen-

$

Skeletal-elements: there are three times more tration of bones can be seen on grid B thatsplinters of elephant tusk in Level 4 on grid Acoincides with the proximity of the two black silt

than on Level 2, while in the latter there are lenses. This greater concentration does not corre-more than double the number of splinters. On spond to any particular skeletal element.grid B, there is a greater concentration of teeth At depth, the main bone accumulations are onin the detrital beds of Level 4 than on the two levels coinciding with the palustrine silt bedscalcareous beds of Level 3. and the calcareous silt beds (Fig. 1). A clearly

predominant NS orientation can be observed for4.3. Cullar de Baza-1 deposit the large bones (Fig. 6). The statistical tests did

not indicate any significant relationship betweenThe proportion of identified and unidentified variables.

remains (Table 2 and Fig. 2) is similar to that

found in Huelago; however, the percentage ofcrania and jaws (Group III ) is higher. To this 5. Bone accumulation processesshould be added the coprolites found by Ruiz

Bustos (1976). As in Huelago and Huescar-1, This section deals with the influence of theisolated teeth of Equus are the most abundant. various factors on the processes of accumulationThe size spectrum shows a pattern similar to and alteration of bones at each site. The sedi-Huescar-1 though the intervals between 110 and mentary characteristics of the deposits and the1045 kg body weight are more scarcely repre- results obtained in the taphonomic study of the

bones were taken into account.sented. The mammal diversity found in Cullar de

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Fig. 6. Horizontal and vertical distributions of bones from Cullar de Baza-1 and rose diagram showing orientation of bones (n,

number of long axis bones included in the rose diagram).

5.1. Huelago-1 vensis, shows an L-shaped distribution which sug-

gests catastrophic mortality (Hulbert, 1982;

Levine, 1983; Behrensmeyer, 1991; Lyman, 1994).The mortality profile (Fig. 7) based on dental

wear of the most abundant species, Equus livenzo- Nevertheless, L-shaped distributions can also be

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Fig. 8. Triangle diagram showing the hydraulic behaviour of bone groups I, II and III (after Voorhies, 1969) for the three Spanish

sites (Huelago-1, Huescar-1 and Cullar de Baza-1) compared with the skeletal-element proportions for: ( 1) average whole mammal;

(2) several vertebrate assemblages of fluvial environments in the Dhok Pathan Formation from Siwalik (Badgley, 1986; Badgley

et al., 1995); (3) several vertebrate assemblages of delta; and (4) fluvial environments in the East Lake Turkana (Behrensmeyer, 1975a).

foreign to the marginal lacustrine environment, the possibility exists that it was erased by abrasionduring transport. The time of subaerial exposuresuggests that the accumulation could be practically

in situ and not transported at all. could have been short for the majority of the

remains. Some bones remained half-buried on theThere could also have been preferential accumu-

lation of bones in or around ponds since, according surface for longer than the rest, suffering root

bioturbation.to the spatial distribution, where some of the sandy

channels eroded the silts, the bones appeared in There is evidence of transport and hydraulic

sorting of bones prior to their final burial: mostboth types of sediment and were not restricted to

the sands. The rare bones that have an algal bones exhibit grooves, impact marks and have

rounded surfaces. Fragile specimens such as verte-covering, although scattered, always show a certain

degree of weathering and indicate areas exposed brae experience more abrasion than large bones

such as metapodials. Hydraulic sorting concen-to the atmosphere for some time before burial.

The morphology and the distribution of the ponds trated the densest parts of the skeleton (teeth) asa lag deposit. Diachronic accumulation is alsois variable in time, as a function of the vertical

oscillations of the water table and erosion by evidenced by the attritional mortality profile

( Fig. 7 ). Taking into account the evidence of trans-fluvial channels.

port and the absence of articulated remains, it is

concluded that the bones were entrained as isolated5.2. Huescar-1

elements and not as whole or articulated parts of

carcasses.No evidence has been found of the activity of

predators and scavengers on the bones although The spatial distribution of bones in Level 2

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reproduces the palaeo-slope of the small delta scattering of the skeletons. Human activity is also

likely, as suggested by the lithic remains presentformed by the discharge of the stream that trans-

ported them at the lacustrine fringe of a lake. In in the deposit (Ruiz Bustos, 1984; Vega Toscano,

1989). Low percentages of ribs and vertebraecontrast, the remains on Level 4 were probably

deposited on a much gentler slope in a distal or compared to long bones also indicates that the

anatomical composition was affected by predatorslateral area of the delta, far from the main outletchannel. Other remains were finally deposited and scavengers (cf. Shipman, 1981a).

Despite the abundance of vegetation in thetowards the interior of the lake and appeared

scattered more or less homogeneously without any swampy environment of Cullar de Baza-1 which

protected the bones from weathering and reducedtrace of preferred distribution, either horizontal or

in pockets. the degree of bone flaking, some of the bones are

strongly weathered. Most bones were exposed forIn general, there is no significant accumulation

of bones in the predominantly lacustrine carbonate a short time to atmospheric agents, as would be

expected in such an environment. In contrast,beds. Most of the specimens are well preserved,

with marks of transport by traction. It is concluded some 25% of the total bone count has deteriorated

through the action of small roots either duringthat the vertebrate site of Huescar-1 records the

accumulation of bones transported by alluvial their stay on the ground or when the remains werestill close to the surface.streams and deposited in the small lacustrine deltas

which mixed with intraclast and bones of aquatic There is no evidence of any supply and selection

of bones by fluvial transport. No rounded orand semi-aquatic habitats (birds, hippopotamus)

that were eroded from the coastal areas during reworked bones or percussion marks have been

found. Besides, articulated specimens also indicatemajor floods.

lack of transportation. The absence of preferential

accumulation of isolated teeth and the relatively5.3. Cullar de Baza-1high percentage of elements of Group III of

Voorhies opposes fluvial influence on the accumu-As in the case of Huelago-1, the mortality

profile (Fig. 7) shows an L-shaped distribution lation (Fig. 8). Sedimentological criteria also sup-

port this conclusion. The fluvial system thatsuggesting catastrophic mortality or seasonal attri-tional mortality. The shores and areas near paludal supplied water to the swampy area transported

only medium to fine sand and apparently it wasenvironments are particularly favoured by animals.

The accumulation of remains of vertebrates on unable to move larger bones such as crania that

have a hydraulic equivalent similar to large peb-this environment has been amply documented

(Brain, 1981; Shipman, 1981a; Andrews, 1990b). bles. The flow depth was very shallow or film-like,

periodically reaching a shallow swampy area soThese observations are confirmed in the Cullar de

Baza-1 deposit where most of the bones occur in that water failed to completely cover the bones

scattered over the surface and could orientate onlylevels interpreted as deposited in swampy

environments. a small percentage of them.

In summary, scavenger and predator action,The presence of predators and scavengers is

evidenced both by their skeletal remains and by including man, must have played a major role in

the accumulation of bone remains on the paludalmarks of their activity: coprolites, bones withmarks of teeth, fractured edges in a crenulated lacustrine margin. The burial of the bones would

correspond to times of flooding, when the bonesform, and greenbone type fractures. The process

of trampling by other animals is a very frequent were initially covered with a film of mud. The

bones were buried near the surface, some relativelycause of the burial and fracturing of bones

(Shipman, 1981a; Behrensmeyer et al., 1986), but rapidly whereas others suffered weathering. In

both cases, the poorly channelled superficial waterno definitive evidence has been here found. In

addition, it is feasible that predators and scaven- in some cases produced further small movements

and the re-organisation of these remains.gers were responsible for the disarticulation and

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6. Discussion Huelago this mud-flat presented shallow ponds

which were periodically swamped and was fur-

rowed with meandering creeks. The Huelago-1We have analysed the qualitative and quantita-

tive differences in the composition of mammal deposit corresponding to one of these small depres-

sions, was a preferential area for the accumulationfossils among the three Plio-Pleistocene deposits

in circum-lake environments from the Guadix- of bones both from the aforementioned area andfrom its margins. The sedimentation was domi-Baza basin. Lake margins are investigated less

than other preservational contexts for vertebrates nated by settling processes and was controlled by

frequent overflows related to heavy rains. In the(see Behrensmeyer and Hook, 1992) and few com-

parable data are available in the literature. We channels, this would cause an increase of the

current energy and transport capacity. Incipienthave compared our results with the observations

of Behrensmeyer (1975a,b) on recent and fossil pedogenic processes occurred during the episodes

of drying, which are not recognised in Cullar deassemblages of delta and fluvial environments in

the East Lake Turkana ( Kenya), recent assem- Baza-1. The burial in the swampy environment of

Cullar de Baza-1 occurred during flooding stages,blages of a closed drainage basin in Amboseli

park, Kenya (Behrensmeyer and Dechant Boaz, when the bones were initially covered with a film

of mud.1980; Behrensmeyer, 1981; Cutler et al., 1999), aswell as several fossil assemblages of fluvial environ- Evidence of the use of this environment by land

mammals is clear although not abundantments in the Dhok Pathan Formation from Siwalik

(Badgley, 1986; Badgley et al., 1995) . The compari- ( Table 5). These animals could have died in situ

in Cullar de Baza-1. It is also probable inson of the main results obtained both in the

sedimentological analysis and in the taphonomic Huelago-1, but no articulated remains were found

(although there were a few dispersed groups overstudy is summarised in Table 5.

The depositional environment of the Huelago a small space). This fact could be explained by

advanced weathering, favoured by the subarialand Cullar de Baza-1 deposits corresponds to

swampy mud-flats that fringed a large lake and exposure during dry periods, and by the activity

of predators, that produced the coprolites andwhere the bones remained dispersed on the surface

and suff

ered weathering. However, in the case of predator-type marks.

Table 5

Taphonomic and sedimentological features of the three Plio-Pleistocene deposits in the Guadix-Baza basin (Granada, Spain)

Huelago-1 Huescar-1 Cullar de Baza-1

Depositional environmenta

General Lake margin Lake margin Lake margin

Type Pond+creek in mud flat Delta Mud flat

Fluvial influence Low High None

Flooding frequency High Deltaic Low

Temporal drying Yes None Not recognised

Bone articulation Clustering of disarticulated bones None Articulated bonesBone damage

Breakage Moderate High Moderate

Weathering High Low (maybe erased) Moderate

Abrasion None Common Rare

Tooth marks Present Absent Present

Root-marks Present Scarce Present

Trampling Present Absent Not recognised

Human activity None None Minor

a Corresponding to lake margin variations.

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By contrast, the depositional conditions of

Huescar-1 correspond to a shallow lacustrine delta

with moderate energy where bones from diverse

areas upstream were sporadically transported and

dumped. In turn, shifting channels caused erosion

and reworking of sediment and bones alreadydeposited there, mixing them with that supplied

by the rivers. This explains the diachronic mixtureFig. 9. Cluster analysis ( UPGMA) of the taxonomic composi-of bone remains with various stages of polishingtion of the three taphonomic assemblages from Guadix-Bazaand rounding, or with a slight degree of erosionbasin in relation with other fluvial assemblages (1) from Dhok

and weathering.Pathan Formation, Siwalik (Badgley, 1986). As a non-paramet-

The results obtained show the number of bones ric measure of similarity, the Spearmans coefficient of rankin Huescar-1 to be greater than in Huelago-1 and order correlation was computed.Cullar de Baza-1 but also with a higher percentage

Table 6of unidentifiable bones. The differences in thePercentages of identified specimens per taxonomic group col-proportions of Voorhies groups of bones indicatelected in excavation carried on in the three Plio-Pleistocene

that the anatomical composition in the three fossil mammal localities in the Guadix-Baza basin (Granada, Spain)assemblages was greatly controlled by sorting pro-

Huelago-1 Huescar-1 Cullar de Baza-1cesses related to hydraulic entrainment and trans-

port (Fig. 8). The low frequency of Group IIICarnivora 0 3.01 3.61

bones (which are the most difficult to transport)Proboscidea 0.59 8.64 3.01

in Huelago-1 is consistent with a more pronounced Equidae 52.66 44.36 57.22fluvial influence than in Cullar de Baza-1 (Fig. 8), Rhinocerotidae 8.87 20.67 2.41

Hippopotamidae 0 11.27 0although the depositional environments andSuidae 0 0 0.6taphonomic features are very similar. In turn, theCervidae 9.46 3.76 7.22

anatomical composition of Huescar-1, with aGiraffidae 3.55 0 0

higher frequency of bones of Group I (immediately Bovidae 21.3 0.37 1.2

transported by flotation or by saltation), than in Artio.Indet. 2.96 0.75 1.81Rodentia 0.59 0 7.83Huelago-1 is consistent with a longer transportLagomorpha 0 0 3.61and a lacustrine delta setting.Aves 0 5.26 0

The taxonomic composition of Huelago-1 isReptilia 0 1.88 11.44

more similar to assemblages of some present fluvial

environments than to Huescar-1 and Cullar de

Baza-1 (Fig. 9). This is evidence that fluvial selec- was sporadic. However, dry periods would have

favoured the penetration of these animals in thetion was an important agent of accumulation.

Surprisingly no carnivore has been found in the area and, in any case, there is a fluvial influence

which could have supplied some remains fromidentifiable fossil remains. However, as already

mentioned, their activity was evidenced. This areas marginal to this environment. Other possible

reasons, such as a hydraulic sorting, are not feasi-absence is noticeable considering the abundance

of bone remains collected ( Table 1). The excava- ble either. The size spectrum obtained in Huelago-1is comparable with those of Huescar-1 and Cullartion was exhaustive and the faunal diversity high

and it is comparable with the results obtained in de Baza-1 (Fig. 2). The number of taxa with

weights between 10 and 45 kg, a range in whichHuescar-1 and Cullar de Baza-1, where carnivore

remains constituted 3% of identifiable remains many species of carnivores are registered, is notice-

ably lower. However, such a decrease is currently(Table 6), and is clearly less than the typical 8

10% for Spanish Neogene localities. found in present environments (Behrensmeyer,

1981). On the other hand, the weight estimatedA possible explanation of this notable absence

could be that the occupation of this swampy area for the total Villafranchian species (for example,

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for those quoted in Villarroya and La Puebla de Flint flakes and large clasts of marble are evi-

dence of the presence of tool using humans in theValverde, Azanza et al., 1989), is on average

higher. To sum up, there is no argument that area (Ruiz Bustos, 1984). With our present knowl-

edge, we can not document the anthropomorphicsatisfactorily explains the absence of carnivores in

Huelago-1 and therefore the random factor has to participation in the fracturing and abrasion of

bones. Independently of the questionable validitybe considered.Another striking feature of the taxonomic com- of the criteria ( Bineford, 1981; Shipman, 1981a;

Behrensmeyer et al., 1986), we found no groovesposition in Huelago-1 is the great diversity of

browsing ruminants. As there is no over-represen- or marks indicative of cut-marks assimilable to

anthropomorphic action.tation of taxa from closed habitats on present

mud-flat environments (Behrensmeyer, 1975a,b), In an environment of this type, it may be

considered that the taphocoenosis would be repre-large wooded or bushy areas should exist in the

surroundings. However, the absence of organic sentative of the original community. Therefore,

the palaeoecological implications which can bematter in large quantities indicates that these

closed areas must have been be some distance deduced a colder environment than in

Huelago-1 (because of a lesser diversity of rodents)away from the lacustrine margin.

Although the diversity of mammals is not much and a less forested environment (by the scantpresence of browsers) appear to be reliable.less, the taxonomic composition in Huescar-1 is

very different with a notably smaller number of

artiodactyl species, particularly in the typical forms

of bush or forest habitats, and the presence of 7. Summary and conclusions

amphibious forms (hippopotamus). The total

diversity is dramatically increased by the large The similarities and differences in the tapho-

nomic features are evaluated with regard to thenumber of bird species, especially aquatic birds.

The taxonomic data are partially consistent with sedimentary processes involved in the deposition

in marginal lacustrine settings of three mammalthe observations of Behrensmeyer (1975a,b) on

Lake Turkana ( Kenya). However, compared with assemblages from the Guadix-Baza basin. Selective

preservation of skeletal-elements and taxa inthese observations, the scarcity of forms indicatingclosed habitats is significant, because these forms different sedimentary facies has been assessed to

determine suitability for further palaeoecologicalare normally over-represented in delta deposits.

From taxonomic, taphonomic and sedimentologi- analysis.

Despite the fact that the mortality in Cullar decal data we conclude that the environment in

Huescar-1 was comparatively more arid than in Baza-1 and Huelago-1 corresponds to the cata-

strophic pattern, other taphonomic featuresHuelago-1.

The taphonomic features as well as the anatomi- observed on the bones themselves indicate that the

accumulation was diachronic as occurred incal and taxonomical composition of the Cullar de

Baza-1 deposit are consistent with the sedimento- Huescar-1. This could be explained by selective-

predation and/or seasonal bone accumulation. Thelogical deductions: the presence of articulated ele-

ments, the relative major frequency of Voorhies latter interpretation coincides with the depositional

environments; seasonality could be producedskeletal elements group III ( Fig. 8 ), average weath-ering and no abrasions, together with clear evi- because sedimentation was controlled by variation

in the water table.dence of the activity of predators and scavengers

as the principal agent in the accumulation of bones Hydraulic factors, as expected, greatly con-

trolled the selective skeletal composition. Although(marks produced on bones and a very high percen-

tage of young adults, Fig. 7) . Note in Fig. 7, senile the depositional environments and taphonomic

features in Huelago-1 and Cullar de Baza-1 areanimals are over-represented because the attrib-

uted value corresponds to a single specimen (a jaw very similar, a more pronounced fluvial influence

was recognised in the former ( Fig. 8).of Equus altidens).

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Again as expected, the different preservational Smith and C. Zazo and an anonymous reviewercircumstances of each sub-environment substan- for their comments. Financial support fromtially constrained the taxonomic composition of Spanish DGICYT Projects: PB88-0008, PB91-0082the preserved bones. Autochthonous fauna only and PB-94-0071 is gratefully acknowledged.occurs in Huescar-1 which is interpreted as sub-

aquatic environments. These results coincide wellwith the data of Behrensmeyer (1975a,b). The Referencesmost intriguing bias is the absence of carnivoresamong the identifiable remains from Huelago-1 Aguirre, E., Soria, M.D., Morales, J., 1981. Accumulated bonesalthough their presence and activity was evidenced. in a Pliocene Cave in Cerro Pelado, Spain. Nat. Geogr. Soc.

Res. Reports 13, 6981.There are no taphonomical or sedimentologicalAlberdi, M.T., Bonadonna, F.P., 1989. Geologa y Paleon-explanations, therefore we assume that it was

tologa de la cuenca de Guadix-Baza. Trabajos N/Q 11,caused by an unknown factor.

1355.Taking into consideration actualistic data, we Alberdi, M.T., Alonso, M.A., Cerdeno, E., Ruiz Bustos, A.,

conclude that differences in taxonomic composi- 1989a. Investigaciones paleontologicas realizadas en lacuenca de Guadix-Baza, entre 1983 y 1987. Trabajos N/Qtion among this mammal assemblage reflect mainly11, 1552.

original habitat preferences of taxa and is consis- Alberdi, M.T., Alcala, L., Azanza, B., Cerdeno, E., Mazo, A.,tent with differences in the surrounding habitats.Morales, J., Sese, C., 1989b. Consideraciones bioestrati-

The great diversity of ruminants, in particulargraficas sobre la fauna de vertebrados fosiles de la cuenca

browsers, indicates wooded or bushy areas in the de Guadix-Baza (Granada, Espana). Trabajos N/Q 11,surroundings of Huelago although not in the 347352.

Alonso, A., Garca del Cura, A., Calvo, J.P., 1988. Significadoimmediate area around the lake margin. Thispaleogeografico de las texturas y acumulaciones de carbo-diversity coincides with that observed in othernatos en perfiles edaficos de la Unidad Intermedia del Mio-Villafranchian localities and represents the greatestceno de la cuenca de Madrid (prov. de Guadalajara).

diversity of artiodactyls known from the Neogene Geogaceta 5, 2933.and Quaternary record in Western Europe Alonso, M.A., 1989. La sedimentacion continental plio-pleisto-

cena en la zona occidental de la Depresion de Guadix-Baza.(Aguirre et al., 1981; Azzaroli, 1995).Evolucion geodinamica del area. Trabajos N/Q 11, 5378.In turn, Huescar-1 presenting a noticeably

Alonso, M.A., 1991. El Plio-Pleistoceno de la cuenca desmaller number of artiodactyls species, despite the Guadix-Baza (zona occidental y area de Cullar de Baza):record of amphibious forms, must to have been

estratigrafa, sedimentologa y evolucion paleogeografica,formed in an open, sparsely forested environment tafonoma de yacimientos de vertebrados. Ph.D. Thesis,with periodical drought, which suggests a more Universidad de Salamanca, Spain (unpublished).

Andrews, P., 1990a. Palaeoecology of the Miocene fauna fromarid climate, in agreement with the sedimentologi-Pasalar, Turkey. J. Hum. Evol. 19, 569582.cal data. Similar sparse forested environment was

Andrews, P., 1990b. Owls, Caves and Fossils. British Museumdeduced for Cullar de Baza-1 where the lesser(Natural History), London.

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