Palaeogeography, Palaeoclimatology, Palaeoecology 265 (2008) 134–139 Contents lists available at ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / p a l a e o Dietary adaptations in an ungulate community from the late Pliocene of Greece Florent Rivals a,⁎, Athanassios Athanassiou b,c a b c ICREA and IPHES (Institut Català de Paleoecologia Humana i Evolució Social), Àrea de Prehistòria, Universitat Rovira i Virgili, Plaça Imperial Tarraco 1, 43005 Tarragona, Spain Hellenic Ministry of Culture, Department of Palaeoanthropology–Speleology, Ardittou 34B, 11636 Athens, Greece National and Kapodistrian University of Athens, Department of Historical Geology and Palaeontology, Panepistimiopolis, 15784 Athens, Greece A R T I C L E I N F O Article history: Received 10 December 2007 Received in revised form 3 April 2008 Accepted 16 May 2008 Keywords: Microwear Mesowear Palaeodiet Ungulates Late Pliocene Greece A B S T R A C T The dietary morphological methods of mesowear and microwear were applied to ungulates of the late Pliocene fauna of Sésklo (Thessaly, Greece). The results provide evidence for the predominance of open grassland in the area, as the most common species, Equus stenonis, was a strict grazer. The rare cervid cf. Croizetoceros ramosus was the only browser. The antelopes (genera Gazella and Gazellospira) yielded discrepant microwear and mesowear results. This is interpreted as an indication of regional or seasonal dietary resource differentiation, inferring that the antelopes were probably mixed feeders that grazed occasionally or periodically. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Fossil herbivore dietary morphology has been frequently used to infer their diet, and subsequently to reconstruct the palaeoenvironmental conditions of the geographical area and the time interval in which they lived. The Pliocene epoch is climatically characterised by a general trend of global cooling, which began in the Miocene and continued into the Pleistocene (Shackleton,1995). The cooling of the environment, associated with considerable drying and increased seasonality in the Mediterranean region (Suc, 1984), may have contributed to the spread of more open landscapes during this time. The late Pliocene deposits from eastern Mediterranean (Greece and Anatolia) and western Mediterranean (southern Iberia) show increasing aridity in this time period (Suc and Popescu, 2005; Fortelius et al., 2006), which largely corresponds to the biozone MN17 of the European mammalian biochronology. Such a climatic shift was followed with a change in vegetation. Grasslands replaced forests so grazing mammals spread at the expense of browsers (Fortelius et al., 2006). More specifically, after an increase of browsers in the MN15, Fortelius et al. (2006) observe a change in the late Pliocene, starting in the MN16 and increasing in MN17, when hypsodont species and grazers increase significantly, whereas browsers gradually decrease. This trend is also observed in the fossil record from Greece, where forest and mixed dwellers are gradually replaced by open habitat dwellers (Kostopoulos et al., 2007). ⁎ Corresponding author. Tel.: +34 977 55 97 34; fax: +34 977 55 95 97. E-mail address: florent.rivals@icrea.es (F. Rivals). 0031-0182/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.palaeo.2008.05.001 Hypsodonty has been used as a proxy for habitat openness and climatic reconstructions, particularly for aridity, and is known to be correlated to climatic changes (Janis and Fortelius, 1988; Fortelius et al., 2002; Fortelius et al., 2006). This relation has been confirmed by several studies (Strömberg, 2002; Strömberg, 2004; Mihlbachler and Solounias, 2006). However, for some extant taxa hypsodonty is known to be different than their diet, for example in American pronghorn (Antilocapra americana) or in many Camelidae. In the fossil record, such discrepancies were revealed in late Miocene North American Equidae (MacFadden et al., 1999), as well as in the Antilocapridae and Camelidae (Semprebon and Rivals, 2007a,b). The evolution of hypsodonty related to aridity is linked to many factors in the composition of the diet such as fibrousness or abrasiveness (due to presence of intracellular silica or extraneous grit) (Fortelius, 1985; Janis, 1988; Janis and Fortelius, 1988; Williams and Kay, 2001). Such changes are also detectable using dental wear analysis, which additionally yields more specific information about the food properties. We propose here to use dental mesowear and microwear analysis to characterize characterise dietary adaptations in an ungulate community from one of those dry areas of the Pliocene. We selected the Sésklo locality because of the important specific diversity and the availability of relatively large samples. 2. Locality, fauna and studied material The locality of Sésklo (Magnesia, Thessaly, Greece) has yielded a rich and diverse mammal fauna, biochronologically dated in the lower MN17 zone, as defined in Mein (1990) (MNQ17 according to Guérin, F. Rivals, A. Athanassiou / Palaeogeography, Palaeoclimatology, Palaeoecology 265 (2008) 134–139 1990, or Saint-Vallier Faunal Unit, according to the Italian authors), late Pliocene (Athanassiou, 1998). It is located in a basin filled with fluviolacustrine clay sediments, about 10 km west of the town of Vólos, the capital of the district of Magnesia. The faunal list, according to Athanassiou (1998) and as revised by more recent data, includes Carnivora [Nyctereutes megamastoides (Pomel, 1843), Vulpes cf. alopecoides Forsyth Major, 1875, Homotherium crenatidens (Fabrini, 1890)], Proboscidea [Anancus arvernensis (Croizet and Jobert, 1828), Mammuthus meridionalis (Nesti, 1825)], Perissodactyla (Equus stenonis Cocchi, 1867, Stephanorhinus sp.), Artiodactyla [cf. Croizetoceros ramosus (Croizet and Jobert, 1828), cf. Dama (Pseudodama) rhenana (Dubois, 1904), cf. Eucladoceros sp., Mitilanotherium martinii (Sickenberg, 1967), Gazella borbonica Depéret, 1884, Gazella bouvrainae Kostopoulos, 1996, Gazella aegea Athanassiou, 2002, Gazellospira torticornis (Aymard, 1854), Gallogoral meneghinii sickenbergi Kostopoulos, 1997, Euthyceros thessalicus Athanassiou, 2002, as well as an undetermined antilopine and one or two large sized bovids] and Aves (Struthio sp.). The uncertain determinations of the cervids derive from the fact that there is a lack of antlers in the material. The available finds are otherwise indistinguishable morphologically and biometrically from the cervid association Eucladoceros–Dama–Croizetoceros known from contemporary European faunas. The ungulate fossils studied here derive from a single, lenticular-shaped accumulation, plausibly produced during a single depositional event. This accumulation, excavated in 1982, yielded the majority of the material available from the site. The artiodactyls and perissodactyls of Sésklo are generally characterised by hypsodont dentitions. This is especially true for the horses, which exhibit an upper molar hypsodonty index – as it is calculated in the equid studies (length at the middle of the crown × 100 / crown height, Eisenmann et al., 1988) – of approximately 40. That means that the upper molars are about 2.5 times higher than long. The antelope (Gazella and Gazellospira) molar hypsodonty index (crown height × 100 / length) is calculated to approximately 125 (accurate calculation is not possible, due to the absence of unworn isolated molars), i.e. they are moderately hypsodont. The enigmatic bovid Euthyceros thessalicus exhibits a similar index of more than 120. The giraffid Mitilanotherium martinii is considered to be mesodont (assumption based on a single juvenile specimen that preserves m1). The only brachyodont ruminant is cf. Croizetoceros ramosus, with an m2 hypsodonty index (as defined above) of up to 74. The studied material belongs to the collections of the Museum of Palaeontology and Geology, National and Kapodistrian University of Athens, Greece. As the microwear and mesowear methods (see below) are applicable to the second molars, only the dentary specimens preserving these teeth (M2 or m2) were sampled. The sampled taxa include Equus stenonis, cf. Croizetoceros ramosus, Euthyceros thessalicus, Gazellospira torticornis, Gazella bouvrainae and Gazella sp. Under Gazella sp. we group the dental material of the genus that is not associated with horn cores and thus cannot be attributed to any of the three Gazella species present in Sésklo. 3. Methods Dental mesowear and microwear were used to analyze palaeodiet. These methods can discriminate between browsing and grazing diets in a wide variety of species including both ungulates (Fortelius and Solounias, 2000; Solounias and Semprebon, 2002) and primates (Semprebon et al., 2004). 3.1. Mesowear A detailed description of the mesowear method is provided by Fortelius and Solounias (2000) and its application towards extinct species is discussed further by Kaiser et al. (2000), Kaiser and Solounias 135 (2003), Mihlbachler and Solounias (2006), Semprebon and Rivals (2007a). Mesowear is based on physical properties of ungulate foods as reflected in the relative amounts of attritive (tooth-on-tooth) wear and abrasive (food-on-tooth) wear on the dental enamel of the occlusal surfaces (Fortelius and Solounias, 2000). Essentially, low abrasion diets, such as those of browsers, result in the maintenance of precise occlusion between the upper and lower teeth because dental wear is primarily attritional (tooth-on-tooth), thus generating an attritional or honing (sharpening) relationship between the upper and lower cusps. In contrast, abrasion-dominated (food-on-tooth) wear, associated with grazing diets, results in more rounded and blunted wear facets and less precise occlusion. Mesowear was scored on the paracone of the M2. Unworn (and marginally worn) teeth, extremely worn teeth, and those with broken or damaged cusp apices are omitted from mesowear analysis. Only adults were demonstrated to have a consistent signal (Fortelius and Solounias, 2000; Rivals et al., 2007a) and are selected. In the original formulation of the method, mesowear was recorded by characterizing characterising the buccal apices of molar cusps as sharp, rounded, or blunt, and the valleys between the cusps as high or low (Fortelius and Solounias, 2000). The original data of Fortelius and Solounias (2000) on extant ungulates were converted into a more simplified univariate score representing a continuum of mesowear stages from the highest and sharpest cusps (0) to cusps that are completely blunted with little or no relief (3) (Rivals et al., 2007b). Intermediate stages of mesowear consisting of more rounded cusp apices with higher and lower levels of cusp relief were assigned 1 and 2, respectively. Teeth with low relief and sharp cusps were assigned a score of 2.5 (Rivals et al., 2007b). Individual scores are then averaged for each sample. 3.2. Microwear The microwear analysis was performed following methods described by Solounias and Semprebon (2002) and Semprebon et al. (2004). Further discussion of this methodology and its application toward dietary reconstruction can also be found in Godfrey et al. (2004) and Palombo et al. (2005). Microwear features were identified and quantified on high resolution epoxy tooth casts at 35× magnification using a Leica SZH10 stereomicroscope. Most microwear features can be categorized as pits and scratches of various sizes and textures. Pits are circular or sub-circular microwear scars. Small pits are relatively shallow, appear bright and shiny, and are usually smaller than 10 μm. Large pits are deeper, wider, less refractive, and larger than 10 μm. Large pits are recorded qualitatively as being present or absent on the wear surface of the tooth. Scratches are elongated microfeatures with straight, parallel sides and can be subcategorized as fine or coarse. Scratch texture is evaluated on the basis of general Table 1 Summary statistics for mesowear and microwear on the M2 from Sésklo Species HI N MWS N PIT cf. Croizetoceros ramosus Equus stenonis Euthyceros thessalicus Gazella sp. Gazella bouvrainae Gazeellospira torticornis 1.05 3 0.7 3 20.50 15.50 5.4 3.4 9 1 2.4 1.5 9 4 17.67 24.72 0 16.50 28.17 0 N3 19 0.7 1 0.8 N 3.4 6 0.9 SCR %0– 17 LP CS ST G 100 0 0 0 21 17.24 28.66 0 1 20.75 20.75 – 10 16.05 28.80 0 10.0 0 0 0 0 – 0 0 1.1 22.2 1 0 38 1 – – 30 1 0 – 0 HI: hypsodonty index (calculated as in Janis, 1988; see caption of Fig. 1); N: number of specimens; MWS: Mesowear score; PIT: average number of pits; SCR: average number of scratches; %0–17 = percentage of specimens displaying less than 17 scratches per counting area; LP: percentage of specimens with large pits; CS: percentage of specimens with cross scratches; ST: scratches texture score (0 = fine scratches only, 1 = fine and coarse scratches, 2 = coarse scratches only); G: percentage of specimens with gouges. 136 F. Rivals, A. Athanassiou / Palaeogeography, Palaeoclimatology, Palaeoecology 265 (2008) 134–139 scratches observed on dental enamel (Solounias and Semprebon, 2002). To approximate pits and scratches frequency, they are counted in a standard 0.4 × 0.4 mm square area on the lingual (inner) band of enamel on the paracone of the upper second molar. 4. Results and interpretation The number of specimens available and identified in the collections for Gazella bouvrainae is very small (N = 1). This small sample is only presented in Table 1 for indication; it will not be used in the discussion section. 4.1. Mesowear Fig. 1. Bivariate plot of mesowear scores against hypsodonty index. The hypsodonty index is defined here as m3 crown height height / / m3 crown width (a universal HI calculation method for all ungulates that is widely used in dietary morphology studies — Janis, 1988). Mesowear scores on extant species calculated from Fortelius and Solounias (2000). appearance and light refractive properties (0 = fine scratches only; 1 = mixture of fine and course, 2 = only coarse scratches). Cross scratches are oriented somewhat perpendicularly to the majority of Mesowear data (Table 1) indicate a high mesowear score for Equus stenonis compared to modern ungulates [MWS = 2.4 (on a scale ranging from 0 to 3)]. It compares to modern grazers such as zebras, Equus burchelli and E. grevyi (Fortelius and Solounias, 2000). This suggests that E. stenonis enjoyed high abrasive vegetation comparable to the food ingested by modern zebras in Africa. The other ungulates from Sésklo, all artiodactyls (Bovidae and Cervidae), have mesowear scores comprised between 0.7 and 1.5 (Table 1). When compared to modern ungulates they fall in the ranges observed for leaf browsers and mixed feeders. However, mesowear should be interpreted in terms of food abrasiveness rather than dietary categories (Fortelius and Solounias, 2000). Results show that those species were feeding on lower abrasive items than E. stenonis. When plotting mesowear scores against hypsodonty index for each species (Fig. 1) it appears that E. stenonis, with a high hypsodonty index (HI = 5.4) and high mesowear score, plots among the modern Fig. 2. Photomicrographs of selected fossil tooth enamel from Sésklo. A. cf. Croizetoceros ramosus (specimen Σ 465); B. Equus stenonis (specimen Σ 1220); C. Euthyceros thessalicus (specimen Σ 396); D. Gazellospira torticornis (specimen Σ 398); All images represent 35 times magnification; scale bar equals 0.2 mm. F. Rivals, A. Athanassiou / Palaeogeography, Palaeoclimatology, Palaeoecology 265 (2008) 134–139 grazers. Euthyceros thessalicus is also located in the grazing morphospace, but closer to the mixed feeders. However, this last observation is based on one specimen only, and is only given here as an indication. At the opposite, cf. Croizetoceros ramosus, with a low hypsodonty index (HI = 1.05), falls near the extant leaf and fruit browsers. Finally, the antelopes (Gazella sp. and Gazellospira torticornis) plot clearly in the area between browsers and grazers, with the modern mixed feeders. 4.2. Microwear Microwear patterns observed for the fossil samples are shown in Fig. 2. Microwear (Table 1) data indicate that the ungulates from Sésklo fall into two categories, leaf browsers and grazers (Fig. 3). None of them seem to be mixed mixed-feeder or fruit browser. Together with the bivariate plot, we used the low scratch range classification from Solounias and Semprebon (2002) where the percentage of specimens (for each sample) displaying less than 17 scratches is computed (for an example see Semprebon and Rivals 2007a). Solounias and Semprebon (2002) reported low ranges (0 to 17%) for grazers and high ranges (64 to 100%) for leaf browsers, whilst while mixed feeders (21 to 70%) and fruit browsers (25 to 86%) overlapped. At Sésklo, the classification is rather drastic, even when sample size is very large. With 100% of counts fewer than 17 scratches, cf. Croizetoceros ramosus classifies as a leaf browser. All the artiodactyls from Sésklo, with 0% of counts under 17 scratches are attributed to the grazers. Both bivariate plot and low scratch range classification give the same interpretation of the data. Microwear indicates that, among all species, only cf. C. ramosus can be classified as a leaf browser. The Fig. 3. Bivariate plot of the average number of pits versus average number of scratches in extant ungulates (data from Solounias and Semprebon, 2002) and fossil samples from Sésklo. Convex hulls are drawn around extant leaf browsing, extant fruit browsing, and extant grazing taxa for ease of comparison. Abbreviations: Leaf-browsers: AA = Alces alces, AM = Antilocapra americana, CL = Camelus dromedarius, DB = Diceros bicornis, BE = Tragelaphus euryceros, GC = Giraffa camelopardalis, LW = Litocranius walleri, TT = Tragelaphus strepsiceros; Fruit-browsers: fCD = Cephalophus dorsalis, fCG = Cephalophus niger, fCN = Cephalophus natalensis, fCS = Cephalophus silvicultor, fOJ = Okapia johnstoni; Grazers: ab = Alcelaphus buselaphus, bb = Bison bison, ct = Connochaetes taurinus, eb = Equus quagga, eg = Equus grevyi, hn = Hippotragus niger, ke = Kobus ellipsiprymnus; Mixed feeders: Ax = Axis axis, Bt = Budorcas taxicolor, Ca = Capricornis sumatraensis, Cc = Cervus elaphus canadensis, Cd = Cervus duvauceli, Ci = Capra ibex, Cu = Cervus unicolor, Gg = Gazella granti, Gt = Gazella thomsoni, Lg = Lama glama, Lv = Lama vicugna, Oc = Ovis canadensis, Om = Ovibos moschatus, Ti = Tragelaphus imberbis, To = Taurotragus oryx, Tq = Tetracerus quadricornis, Tr = Boselaphus tragocamelus, Ts = Tragelaphus scriptus. 137 other five species (Equus stenonis, Euthyceros thessalicus, Gazellospira torticornis, Gazella bouvrainae and Gazella sp.) are classified by microwear as grazers. At Sésklo, the number of pits observed for grazers is relatively high compared to typical modern grazers (Fig. 3). High numbers of pits are known in modern species such as camels and llamas and are indicators of dry environments (Solounias and Semprebon, 2002). They were also reported for many fossil hypsodont ungulates such as Antilocapridae (Semprebon and Rivals, 2007a) or Camelidae (Semprebon and Rivals, 2007b). The presence of relatively high density of pits for all artiodactyls at Sésklo reveals a relative aridity of the environment. 5. Discussion Palaeoecological reconstructions in palaeozoology are traditionally based on the faunal composition and the functional morphology of the studied fossil mammals. The equids and bovids of Sésklo constitute respectively 31% and 43% of the fauna, while the cervids represent only 8% of it (estimation based on the Minimum Number of Individuals — Athanassiou, 1998). This clear predominance of the generally open habitat dwellers over the typically forest ones is a good indication for an open environment at Sésklo during the late Pliocene. Moreover, Equus stenonis from Sésklo exhibits additional ecomorphological adaptations that also indicate open and rather dry environmental conditions, as well as a diet based on abrasive food: very long and fairly slender distal limb segments, relatively narrow distal phalanges, wide and robust mandibular symphysis, and extreme hypsodonty (Athanassiou, 2001). Its hypsodonty index is comparable to that given by Fortelius and Solounias (2000) for the extant zebras E. burchelli and E. grevyi. The new evidence from both mesowear and microwear analysis corroborates the above mentioned ecomorphology-based conclusions, also indicating open environmental conditions and diet on abrasive items, especially for Equus stenonis. Because of the presence of cervids, it is difficult to refute the hypothesis that some woodland existed around the site. However, Croizetoceros might also feed on browse available in non-forested areas, as it is the case with some extant small-bodied deer species, as Dama dama or Capreolus capreolus, which exploit resources in both forested as well as open areas (Feldhamer et al., 1988; Hutchins et al., 2003, p. 269, 366, 388). In both cases, competition with other ungulates and the partitioning of the available resources may explain this dietary segregation. The different trophic interpretation of the antelopes inferred using mesowear and microwear methods may well rely on the nature of these methods. The mesowear method studies the cumulative and average end result on occlusal morphology, produced by attrition and abrasion over a long feeding period in the animal's life, usually several months or years (Fortelius and Solounias, 2000). On the contrary, the microwear pattern is the direct result of the abrasive action of food items on tooth enamel during the last few meals (Solounias and Semprebon, 2002). Thus, the results concerning the antelopes of Sésklo could indicate a difference between their average trophic practices and the last meals content. A possible interpretation for this would be a regional or seasonal variability in the type of ingested vegetation, with a prevailing mixed-feeder diet. This is in accordance with the moderate hypsodonty that characterises Gazella and Gazellospira from Sésklo. Their feeding habits could be similar to that of the extant Near East gazelles (e.g. Gazella gazella), which use seasonally varying food resources, grazing on fresh grasses during winter and browsing on leaves, twigs and pods during summer, when green food is scarce (Mendelsson et al., 1995). The trophic regime interpretation of the gazelles from Sésklo may, however, be affected by the fact that their dental remains are indeterminable at specific level. Considering the three gazelle species present at Sésklo (as documented by their horn cores) and the fact that meso- and microwear results are 138 F. Rivals, A. Athanassiou / Palaeogeography, Palaeoclimatology, Palaeoecology 265 (2008) 134–139 averaged, it is certain that any potential trophic differentiation among the gazelle species will be suppressed in these results. Nevertheless, the specimens attributed to Gazella sp. exhibit a very low variation in their micro- and mesowear scores (standard deviation (SD) for mesowear score is 0.8; for microwear the SD for pits and scratches is 2.7 and 4.5, respectively). Such a low variation compared to other fossil or extant ungulates, both in meso- and microwear, indicates a similar diet for all individuals in that sample. This suggests that there are hardly any dietary differences among the species which are potentially included in Gazella sp. Additional evidence for browsing habits of the Sésklo antelopes comes from their craniodental morphology (Janis, 1995; Mendoza et al., 2002), as they exhibit wide braincase angles and relatively long premolar rows: the premolar/molar ratio is 65.6% for the upper tooth row of Gazella bouvrainae, while the same ratio is 56–58.8% for the lower tooth rows of Gazellospira torticornis and 63% for lower tooth rows of Euthyceros thessalicus. This environmental context is different from that reported for similarly aged West-European localities, which indicate more forested environments and, in most cases, more humid climatic conditions. At Saint-Vallier (Drôme, France), a reference site for the MN17 biozone, the mammalian community reflects a mosaic environment of steppe punctuated by open woodland under a relatively moist and temperate climate (Guérin et al., 2004). At this locality, dental wear analysis indicated more flexible adaptations for the cervids towards mixed feeding (Valli and Palombo, 2008) confirming the presence of a mosaic environment. Other West-European localities, as La Puebla de Valverde in Spain and the somewhat more recent Senèze and Chilhac in France and Olivola in Italy, seem to indicate a similar mosaic environment, as inferred by their faunal compositions (Guérin et al., 2004). SaintVallier, as well as Chilhac, Senèze and La Puebla de Valverde, yielded considerably more cervids (the same taxonomic association but in greater abundance) than Sésklo, implying more extensive tree cover. The ecomorphological characters of Equus stenonis at La Puebla de Valverde and Olivola, though, point to a dryer climate in comparison to French localities (Eisenmann and Guérin, 1984), which is in accordance with their relatively southern location. In the Balkan region, the Bulgarian locality of Varshets, which is dated to MN17, has yielded a fauna quite rich in forest taxa, indicating a mixed environment of forests and open regions (Spassov and Crégut-Bonnoure, 1999), probably similar to that of Saint-Vallier. The Northern Greek faunas of Vólax and Dafneró, which are contemporary and taxonomically almost identical to that of Sésklo, as well as the also isochronous fauna of Vaterá (Lésbos Island), do not differentiate palaeoecologically from it; they indicate an open and dry landscape (Kostopoulos and Koufos, 2000; De Vos et al., 2002). However, the cervids are better represented in Vólax and Dafneró, implying greater browsing availability in these localities than in Sésklo. 6. Conclusion The results from the application of mesowear and microwear methods to ungulate dental material from Sésklo indicate the predominance of open and dry environment at the area, punctuated by open woodland or thickets. Equus stenonis was the main grazer species. The antelopes Gazella and Gazellospira, and the large bovid Euthyceros thessalicus were probably mixed feeders that used to graze on seasonal or regional basis. The small cervid cf. Croizetoceros ramosus was the only exclusively browsing species among the plant eaters of the Sésklo fauna. This interpretation is in accordance with the horse and antelope ecomorphological characters. At Sésklo, ungulates have quite diversified feeding behaviours (one grazer, one browser, and two mixed feeders). Thus, in terms of resource competition, the overlap of the ecological niches was quite reduced. When compared to other European late Pliocene localities, Sésklo shows affinities with the southern European sites in the Iberian and Italian peninsulas. In all those localities the environment was reported to be more arid than in other parts of Europe — especially in Western Europe. Even during these times of aridity, ungulates managed to keep a high relative species diversity (and dietary diversity) through resource partitioning. Acknowledgements We thank the two anonymous reviewers whose comments and suggestions greatly improved the manuscript. We are also grateful to Scott Holman for linguistically editing a previous draft of this manuscript. References Athanassiou, A., 1998. Contribution to the study of the fossil mammals of Thessaly. PhD Thesis (1996). National and Kapodistrian University of Athens. Gaia 5, 1-393. (in Greek). Athanassiou, A., 2001. New data on the Equus stenonis Cocchi, 1867 from the late Pliocene locality of Sésklo (Thessaly, Greece). Geodiversitas 23, 439–469. De Vos, J., van der Made, J., Athanassiou, A., Lyras, G., Sondaar, P.Y., Dermitzakis, M.D., 2002. Preliminary note on the Late Pliocene fauna from Vatera (Lesvos, Greece). Annales Géologiques des Pays Helléniques 39 (A), 37–70. Eisenmann, V., Guérin, C., 1984. Morphologie fonctionnelle et environnement chez les Périssodactyles. Géobios. Mémoire Spécial 8, 69–74. Eisenmann, V., Alberdi, M.T., De Giuli, C., Staesche, U., 1988. Methodology. In: Woodburne, M.O., Sondaar, P. (Eds.), Studying Fossil Horses. E.J. Brill, Leiden, pp. 1–71. Feldhamer, G.A., Farris-Renner, K.C., Barker, C.M., 1988. Dama dama. Mammalian Species 317, 1–8. Fortelius, M., 1985. Ungulate cheek teeth: developmental, functional, and evolutionary interrelations. Acta Zoologica Fennica 180, 1–76. Fortelius, M., Solounias, N., 2000. Functional characterization of ungulate molars using the abrasion–attrition wear gradient: a new method for reconstructing paleodiets. American Museum Novitates 3301, 1–36. Fortelius, M., Eronen, J., Jernvall, J., Liu, L., Pushkina, D., Rinne, J., Tesakov, A., Vislobokova, I., Zhang, Z., Zhou, L., 2002. Fossil mammals resolve regional patterns of Eurasian climate change over 20 million years. Evolutionary Ecology Research 4, 1005–1016. Fortelius, M., Eronen, J., Liu, L., Pushkina, D., Tesakov, A., Vislobokova, I., Zhang, Z., 2006. Late Miocene and Pliocene large land mammals and climatic changes in Eurasia. Palaeogeography, Palaeoclimatology, Palaeoecology 238, 219–227. Godfrey, L.R., Semprebon, G.M., Jungers, W.L., Sutherland, M.R., Simons, E.L., Solounias, N., 2004. Dental use wear in extinct lemurs: evidence of diet and niche differentiation. Journal of Human Evolution 47, 145–169. Guérin, C.,1990. Biozones or mammal units? Methods and limits in biochronology. In: Lindsay, E.H., Fahlbusch, V., Mein, P. (Eds.), European Neogene Mammal Chronology. NATO ASI Series (A: Life Sciences). Plenum Press, New York, pp. 119–130. Guérin, C., Faure, M., Argant, A., Argant, J., Crégut-Bonnoure, E., Debard, E., Delson, E., Eisenmann, V., Hugueney, M., Limondin-Lozouet, N., Martin Sufirez, E., Mein, P., Mourer-Chauviré, C., Parenti, F., Pastre, J.-F., Sen, S., Valli, A., 2004. Le gisement pliocène supérieur de Saint-Vallier (Drôme, France). Synthèse biostratigraphique et paléoécologique. Geobios 37, S349–S360. Hutchins, M., Kleiman, D.G., Geist, V., McDade, M.C. (Eds.), 2003. 2nd edition. Grzimek's Animal Life Encyclopedia, vol. 15. Gale, Farmington Hills. Janis, C.M., 1988. An estimation of tooth volume and hypsodonty indices in ungulate mammals, and the correlation of these factors with dietary preferences. In: Russell, D.E., Santoro, J.-P., Sigogneau-Russell, D. (Eds.), Teeth Revisited (Proceedings of the VIIth International Symposium on Dental Morphology, Paris, 1986). Mémoires du Muséum National d'Histoire Naturelle (C), 53, pp. 367–387. Paris. Janis, C.M., 1995. Correlations between craniodental morphology and feeding behavior in ungulates: reciprocal illumination between living and fossil taxa. In: Thomason, J.J. (Ed.), Functional Morphology in Vertebrate Paleontology. Cambridge University Press, Cambridge, pp. 76–98. Janis, C.M., Fortelius, M., 1988. On the means whereby mammals achieve increased functional durability of their dentitions with special reference to limiting factors. Biological Reviews of the Cambridge Philosophical Society 63, 197–230. Kaiser, T.M., Solounias, N., 2003. Extending the tooth mesowear method to extinct and extant equids. Geodiversitas 25, 321–345. Kaiser, T.M., Solounias, N., Fortelius, M., Bernor, R.L., Schrenk, F., 2000. Tooth mesowear analysis on Hippotherium primigenium from the Vallesian Dinotheriensande (Germany)—a blind test study. Carolinea 103–114. Kostopoulos, D.S., Koufos, G.D., 2000. Palaeoecological remarks on Plio-Pleistocene mammalian faunas. In: Koufos, G.D., Ioakim, C.E. (Eds.), Interim Colloquium RCMNS “Mediterranean Neogene Cyclostratigraphy in marine–continental palaeoenvironments”, Patras, 1998. Special Publications of the Geological Society of Greece, 9, pp. 139–150. Athens. Kostopoulos, D.S., Palombo, M.-R., Alberdi, M.-T., Valli, A.M.F., 2007. Pliocene to Pleistocene large mammal diversity and turnover in North Mediterranean region: the Greek Peninsula with respect to the Iberian and Italian ones. Geodiversitas 29, 401–419. MacFadden, B.J., Solounias, N., Cerling, T.E., 1999. Ancient diets, ecology and extinction of 5-million-year-old horses from Florida. Science 283, 824–827. F. Rivals, A. Athanassiou / Palaeogeography, Palaeoclimatology, Palaeoecology 265 (2008) 134–139 Mein, P., 1990. Updating of MN zones. In: Lindsay, E.H., Fahlbusch, V., Mein, P. (Eds.), European Neogene Mammal Chronology. NATO ASI Series (A: Life Sciences). Plenum, New York, pp. 73–90. Mendelsson, H., Yom-Tov, Y., Groves, C.P., 1995. Gazella gazella. Mammalian Species 490, 1–7. Mendoza, M., Janis, C.M., Palmqvist, P., 2002. Characterizing complex craniodental patterns related to feeding behaviour in ungulates: a multivariate approach. Journal of Zoology 258, 223–246. Mihlbachler, M.C., Solounias, N., 2006. Coevolution of tooth crown height and diet in oreodonts (Merycoidodontidae, Artiodactyla) examined with phylogenetically independent contrasts. Journal of Mammalian Evolution 13, 11–36. Palombo, M.R., Filippi, M.L., Iacumin, P., Longinelli, A., Barbieri, M., Maras, A., 2005. Coupling tooth microwear and stable isotope analyses for palaeodiet reconstruction: the case study of Late Middle Pleistocene Elephas (Palaeoloxodon) antiquus teeth from Central Italy (Rome area). Quaternary International 126–128, 153–170. Rivals, F., Mihlbachler, M.C., Solounias, N., 2007a. Effect of ontogenetic-age distribution in fossil samples on the interpretation of ungulate paleodiets using the mesowear method. Journal of Vertebrate Paleontology 27, 763–767. Rivals, F., Solounias, N., Mihlbachler, M.C., 2007b. Evidence for geographic variation in the diets of late Pleistocene and early Holocene Bison in North America, and differences from the diets of recent plains Bison. Quaternary Research 68, 338–346. Semprebon, G.M., Rivals, F., 2007a. Was grass more prevalent in the pronghorn past? An assessment of the dietary adaptations of Miocene to recent Antilocapridae (Mammalia: Artiodactyla). Palaeogeography, Palaeoclimatology, Palaeoecology 253, 332–347. Semprebon, G.M., Rivals, F., 2007b. Hypsodont browsing: camel and pronghorn dietary reconstruction through deep time. Journal of Vertebrate Paleontology 27, 144A suppl. Semprebon, G.M., Godfrey, L.R., Solounias, N., Sutherland, M.R., Jungers, W.L., 2004. Can low-magnification stereomicroscopy reveal diet? Journal of Human Evolution 47, 115–144. 139 Shackleton, N.J., 1995. New data on the evolution of Pliocene climatic variability. In: Vrba, E.S., Denton, G.H., Partridge, T.C., Burckle, L.H. (Eds.), Paleoclimate and Evolution, with Emphasis on Human Origins. Yale University Press, New Haven, pp. 242–248. Solounias, N., Semprebon, G., 2002. Advances in the reconstruction of ungulate ecomorphology with application to early fossil equids. American Museum Novitates 3366, 1–49. Spassov, N., Crégut-Bonnoure, E., 1999. Premières données sur les Bovidae Villafranchiens de Boulgarie. Comptes Rendus de l'Académie des Sciences 328, 493–498. Strömberg, C.A.E., 2002. The origin and spread of grass-dominated ecosystems in the late Tertiary of North America: preliminary results concerning the evolution of hypsodonty. Palaeogeography, Palaeoclimatology, Palaeoecology 177, 59–75. Strömberg, C.A.E., 2004. Using phytolith assemblages to reconstruct the origin and spread of grass-dominated habitats in the Great Plains during the late Eocene to early Miocene. Palaeogeography, Palaeoclimatology, Palaeoecology 207, 239–275. Suc, J.-P., 1984. Origin and evolution of the Mediterranean vegetation and climate in Europe. Nature 307, 429–432. Suc, J.-P., Popescu, S.-M., 2005. Pollen records and climatic cycles in the North Mediterranean region since 2.7 Ma. In: Head, M.J., Gibbard, P.L. (Eds.), Early-Middle Pleistocene Transitions: The Land–Ocean Evidence. Geological Society, Special Publications, 247, pp. 147–158. London. Valli, A.M.F., Palombo, M.R., 2008. Feeding behaviour of middle-size deer from the Upper Pliocene site of Saint-Vallier (France) inferred by morphological and micro/ mesowear analysis. Palaeogeography, Palaeoclimatology, Palaeoecology 257, 106–122. Williams, S.H., Kay, R.F., 2001. A comparative test of adaptive explanations for hypsodonty in ungulates and rodents. Journal of Mammalian Evolution 8, 207–229.