Hypsodonty Index Research Articles

The Inter-Relationship between Dietary and Environmental Properties and Tooth Wear: Comparisons of Mesowear, Molar Wear Rate, and Hypsodonty Index of Extant Sika Deer Populations

In reference to the evolutionary trend of increasing cheek tooth height in herbivorous ungulates, the causes of dental abrasion have long been debated. Interspecific comparisons of extant ungulates have revealed that both phytoliths in grass and external abrasive matter may play important roles. Using analysis of extant sika deer living in various environments and showing continuous latitudinal variation in food habits from northern grazing to southern browsing, we quantitatively evaluated the influence of dietary and environmental properties on three dental variables: mesowear score (MS), molar wear rate, and M3 hypsodonty index. We used 547 skulls and 740 mandibles from 16 populations of sika deer to obtain the dental measurements. We found that only graminoid proportion in diet correlated with MS and the molar wear rate, implying that phytoliths in grass abrade dental tissues. In contrast, annual precipitation in habitat was not correlated with any of the dental variables. We also found a significant correlation between the molar wear rate (selective pressure for high-crowned molars) and the M3 hypsodonty index of extant sika deer, implying an evolutionary increment in molar height corresponding to the molar wear rate. Our intraspecific comparative analyses provide further support for use of mesowear analysis as a paleodiet estimation method; it not only reveals staple food types (graminoids or dicots) but also implies regional or seasonal variation in the diet of the species.

Occlusal enamel complexity and its implications for lophodonty, hypsodony, body mass, and diet in extinct and extant ungulates

Tooth morphology and rates of wear have strong controls on how well mammals survive in their habitats. Herbivorous mammals, specifically ungulates, combat the effects of wear through a combination of changing the occlusal (chewing surface) enamel length, and changing hypsodonty (relative height of tooth). Changes in these two attributes are most notably seen in the fossil record of ungulates as they adapted to living in cooler, drier, and more open habitats. We expect enamel length and hypsodonty to be greater in ungulate taxa that feed on grasses than in non-grass feeders. We tested this hypothesis by digitally photographing 213 maxillary tooth rows from 84 species of extinct and extant ungulates (n=1083 teeth) and measuring their occlusal enamel length and true occlusal area. We then statistically compared the influences of taxonomy, feeding strategy, tooth position, and tooth area on both hypsodonty and occlusal enamel length using principal components analysis (PCA) and a nested multivariate analysis of variance (MANOVA). The results of our PCA indicated a strong correlation between enamel length and tooth area, but little correlation of either with hypsodonty. Our nested MANOVA showed that tooth position had no significant relationship with hypsodonty (p=0.1539), while all other factors were significant for both hypsodonty and occlusal enamel length. Our results suggest that the occlusal enamel length in ungulate teeth is constrained by both the size of the tooth (and, by proxy, the mass of the individual) and diet. Absolute tooth crown height is similarly affected by a combination of body size and diet, leading to the use of a ratio, hypsodonty index, to characterize the diet component. We propose a similar ratio, the occlusal enamel index (OEI) which reduces the effect of body mass to clearly indicate the component of enamel length determined by abrasiveness of ingested material.

The fossil history of Grévy's zebra (Equus grevyi) in equatorial East Africa

AbstractAimWithin the last several decades, Grévy's zebra (Equus grevyi) has undergone a massive reduction in geographical range and population size, largely as the result of human impacts. To place its recent decline in a deeper prehistoric context, and to understand the factors mediating its range and abundance over geological time frames, this study examines the fossil history of Grévy's zebra in equatorial East Africa.LocationEquatorial East Africa.MethodsPresence/absence data for ungulates recovered from fossil sites spanning the last c. 400,000 years in Kenya and Ethiopia were compiled from the literature and from previously unreported palaeontological sites. Associations between Grévy's zebra and other taxa were examined using principal coordinates analysis and non‐random species pairs were identified using a Bayesian approach. Changes in rainfall were reconstructed using the average hypsodonty index of ungulate species from fossil assemblages.ResultsGrévy's zebra was common during dry phases of the Pleistocene and was found to the south and west of its historical range, coinciding with an expansion of arid grasslands. At the onset of the Holocene, Grévy's zebra was extirpated from southern Kenya and almost completely disappeared from the fossil record. Grévy's zebra was associated with several specialized grazers that became extinct by the end of the Pleistocene. These extinctions and the decline of Grévy's zebra from the Pleistocene to the Holocene are explained by increased precipitation and the consequent loss of arid grasslands at the Pleistocene–Holocene transition. Grévy's zebra is never associated with domestic livestock, unlike the widespread plains zebra.Main conclusionsGrévy's zebra thrived in equatorial East Africa during periods of the Pleistocene when environmental conditions favoured an expansion of arid grasslands. Environmental change across the Pleistocene–Holocene transition contributed to decreases in the range size and abundance of Grévy's zebra, setting the stage for the anthropogenic decline observed in recent decades. The spread of pastoralists in the middle Holocene may have additionally contributed to its prehistoric decline. Contemporary climate change warrants further consideration in planning for the long‐term survival of Grévy's zebra.

Stable isotopes provide independent support for the use of mesowear variables for inferring diets in African antelopes

We examine the relationship between mesowear variables and carbon and nitrogen isotopes in 16 species of African antelope (Mammalia: Bovidae). We show significant differences in carbon and nitrogen isotope values between individuals exhibiting sharp versus round cusps, and high versus low occlusal relief. We show significant correlations between mesowear variables and both carbon and nitrogen isotopes. We find significant correlations between mesowear score and nitrogen, but not carbon isotopes. Finally, we find no significant correlations between hypsodonty index and either isotope examined. Our results provide strong support for the use of mesowear variables in palaeodietary reconstructions of antelopes. Our results further suggest that for the antelopes examined here, mesowear signals are a direct result of diet, while hyposodonty may be the result of phylogenetic legacy.

Hypsodonty and tooth facet development in relation to diet and habitat in herbivorous ungulates: implications for understanding tooth wear

Abstract The evolution of high‐crowned teeth or hypsodonty in herbivorous mammals is widely interpreted as a species‐specific adaptation to increasingly wear‐inducing diets and environments at evolutionary time scales, with internal abrasives (such as phytoliths in grasses) and/or external abrasives (such as dust or grit) as putative causative factors. The mesowear score (MS) instead describes tooth wear experienced by individual animals during their lifetime. Under the assumption that the abrasiveness that causes the MS in individuals is the same abrasiveness to which species adapted by evolving hypsodonty, one would expect a close correlation between the MS and the hypsodonty index (HI). Alternatively, if these two measures reflect different aspects of wear, one would expect differences in the way that proxies of diet or environment/climate correlate with each parameter. In order to test these hypotheses, we collated a dataset on the HI, MS, percentage of grass in the natural diet (%grass), habitat (open, intermediate, closed) and annual precipitation (PREC) in extant mammalian herbivores. The availability of a quantitative MS constrained the dataset to 75 species. Data were analysed with and without phylogenetic generalized least squares. Correlations with PREC were stronger for HI than for MS, whereas correlations with %grass were similar for HI and MS. Habitat had a significant influence on the relationship with %grass for HI but not for MS. Habitat also had a significant influence on the relationship between HI and MS. MS improved the predictive power of HI for %grass, but not for PREC. These results suggest that while the MS indicates predominantly the wear effect of the diet (internal abrasives), HI represents an adaptation to a wear effect that comprises both diet and environment (external abrasives). The additional environmental wear effect must reduce tooth height without causing macroscopic changes in tooth facet development as described by the MS. The most parsimonious explanation for the apparent discrepancy between HI and MS is that external abrasives of very fine particle size play a major role in naturally occurring tooth wear. The experimental testing of this hypothesis will enhance our understanding of the processes involved in tooth wear.

EVALUATING HABITATS AND FEEDING HABITS THROUGH ECOMORPHOLOGICAL FEATURES IN GLYPTODONTS (MAMMALIA, XENARTHRA)

The goal of this study is to evaluate ecomorphological variables in glyptodonts from different ages (Miocene to early Holocene), clades, and sizes, with the purpose of inferring their habitats and feeding habits. The analyses included estimation of body masses and three variables: relative muzzle width (RMW), hypsodonty index (HI), and dental occlusal surface area (OSA). RMW allows the distinction of two main groups: the small-sized early Miocene propalaehoplophorids were selective feeders, while the larger post-Miocene forms were more bulk feeders. The Pleistocene Glyptodon appears as an exception, implying a reversion to a selective feeding behavior. The relation between RMW and HI allows discriminating feeding niche partitioning in glyptodonts. Among the early Miocene propalaehoplophorids, Eucinepeltus would have been a highly selective feeder in relatively closed environments, Propalaehoplophorus a highly selective feeder in moderately open habitats, and Cochlops a less selective feeder in moderately open habitats. Among the large Pliocene and Pleistocene taxa, cf. Neuryurus and Neosclerocalyptus were probably bulk feeders in relatively open environments, while Panochthus and Doedicurus were bulk feeders in open environments. Alternative interpretations can be assessed for Glyptodon: it was a more selective feeder in closer habitats, or had a different feeding behavior, browsing on specific plants at higher levels from the ground, and/or a specialized physiology. The late Miocene and Pliocene forms (Hoplophractus, Eosclerocalyptus, and Urotherium) were probably intermediate between the Miocene and the Pleistocene ones.

Another one bites the dust: faecal silica levels in large herbivores correlate with high-crowned teeth.

The circumstances of the evolution of hypsodonty (= high-crowned teeth) are a bone of contention. Hypsodonty is usually linked to diet abrasiveness, either from siliceous phytoliths (monocotyledons) or from grit (dusty environments). However, any empirical quantitative approach testing the relation of ingested silica and hypsodonty is lacking. In this study, faecal silica content was quantified as acid detergent insoluble ash and used as proxy for silica ingested by large African herbivores of different digestive types, feeding strategies and hypsodonty levels. Separate sample sets were used for the dry (n = 15 species) and wet (n = 13 species) season. Average faecal silica contents were 17–46 g kg−1 dry matter (DM) for browsing and 52–163 g kg−1 DM for grazing herbivores. No difference was detected between the wet (97.5 ± 14.4 g kg−1 DM) and dry season (93.5 ± 13.7 g kg−1 DM) faecal silica. In a phylogenetically controlled analysis, a strong positive correlation (dry season r = 0.80, p < 0.0005; wet season r = 0.74, p < 0.005) was found between hypsodonty index and faecal silica levels. While surprisingly our results do not indicate major seasonal changes in silica ingested, the correlation of faecal silica and hypsodonty supports a scenario of a dominant role of abrasive silica in the evolution of high-crowned teeth.

Trends in the paleodietary habits of fossil camels from the Tertiary and Quaternary of North America

Dietary adaptations of both Tertiary and Quaternary representatives of North American Camelidae were examined through deep evolutionary time (via hypsodonty index), though ecological time (via mesowear analysis), and through the last few days of life (via microwear) by examining molar teeth. Fossil samples are from the Great Plains, Great Basin, Arizona, and Florida and span from the early late Eocene (late Chadronian–early Orellan) to the late Pleistocene (Rancholabrean). Results were compared to those obtained on modern camels and llamas and other ungulates of known dietary behavior. Camels apparently exploited open habitats early on in their evolution as evidenced by the extreme pitting of their enamel surfaces. Grasses were likely consumed early on in their history (e.g., Poebrotherium) but the vast majority of taxa were committed browsers. Results show that the hypsodonty pattern (deep time adaptation) and mesowear pattern (cumulative abrasion index) are very similar. Hypsodonty indices and mesowear scores decrease in the middle Miocene, a time when a few taxa also incorporate fruit and/or seeds in their browse. Crown height and dietary abrasion increase in the late Miocene and Pliocene, a time when some grazers and mixed feeders also appear, but then decrease in Pleistocene and Recent forms.

Hypsodonty in the Pleistocene Ground SlothMegalonyx: Closing the “Diastema” of Data

Hypsodonty in Pleistocene ground sloths was reported by Bargo et al. (2006), but no data was provided for mega− lonychids. Herein, hypsodonty indices (HI) are presented for 22 Megalonyx specimens (mean = 1.06, SD = 0.10), and statistical analysis suggests that there were no significant changes in HI during the ontogeny or phylogeny of the ge− nus during the Pleistocene.

Biogeochemical and Ecomorphological Inferences On Prey Selection and Resource Partitioning Among Mammalian Carnivores In An Early Pleistocene Community

Abstract Biogeochemical (δ13C, δ15N, and δ18O values) and ecomorphological analyses of the early Pleistocene fauna of Venta Micena (Orce, Guadix-Baza basin, SE Spain) provide interesting clues on the physiology, dietary regimes, habitat preferences, and ecological interactions of large mammals. Such inferences are useful in deciphering aspects of paleocommunity structure and predator-prey relationships. Specifically, the hypsodonty index combined with δ13C values allows classifying the ungulates among grazers from open habitat (Equus altidens, Bison sp., Praeovibos sp., Hemitragus albus, Hippopotamus antiquus, and Mammuthus meridionalis), mixed feeders (Soergelia minor and Pseudodama sp.), and browsers from canopy areas (Stephanorhinus sp. and Praemegaceros cf. verticornis). Given that δ13C values indicate that all these herbivores fed exclusively on C3 plants, significant differences in isotopic values between perissodactyls (monogastric, hindgut fermenters) and ruminants (foregut fermenters) reflect dif...

Tracing the ecophysiology of ungulates and predator–prey relationships in an early Pleistocene large mammal community

Research into the reconstruction of ancient communities in terms of dietary regimes, habitat preferences and ecological interactions of species has focused predominantly on biogeochemistry or ecomorphology alone and not in combination. The Venta Micena site (Orce, Guadix–Baza basin, SE Spain) has an early Pleistocene vertebrate assemblage with exceptional biomolecular preservation. Collagen was successfully extracted from 77 bone samples of 18 species of large mammals, which allowed analyses of carbon- and nitrogen-isotopes. δ 13C, δ 15N and δ 18O ratios combined with ecomorphological indexes provide interesting clues on the autecology and palaeophysiology of extinct species, which help in deciphering aspects of community trophic structure and predator–prey interactions. Specifically, morphometric ratios (e.g., hypsodonty index and relative length of the lower premolar tooth row; [Palmqvist, P., Gröcke, D.R., Arribas, A., Fariña, R. 2003. Paleoecological reconstruction of a lower Pleistocene large mammals community using biogeochemical ( δ 13C, δ 15N, δ 18O, Sr:Zn) and ecomorphological approaches. Paleobiology 29, 204–228.]) allow classifying the ungulates among grazers ( Equus altidens, Bison sp., Praeovibos sp., Hemitragus albus, Hippopotamus antiquus, and Mammuthus meridionalis), mized-feeders ( Soergelia minor and Pseudodama sp.) and browsers ( Stephanorhinus sp. and Praemegaceros cf. verticornis). However, δ 13C values reveal that these ungulates consumed exclusively C 3 plants and significant differences in isotopic values between perissodactyls (monogastric, hindgut fermenters) and ruminants (foregut fermenters) must reflect physiological differences related to their rates of methane production and digestive efficiency. δ 18O ratios allow the interpretation of the dietary water source of these species, suggesting that fallow deer Pseudodama sp., goat H. albus and ovibovine S. minor obtained a significant fraction of their metabolic water from the vegetation consumed. Carnivore species have higher δ 15N values than herbivores, which records the isotopic enrichment expected with an increase in trophic level. However, the unexpectedly high δ 15N values of hippo H. antiquus and muskoxen Praeovibos sp. suggest that these ungulates predominantly consumed aquatic plants and lichens, respectively. Inferences on predator–prey relationships within this ancient community, derived from the dual linear mixing model, indicate resource partitioning among sympatric predators, suggesting that sabre-tooth Megantereon whitei and jaguar Panthera cf. gombaszoegensis were ambushers of forest environments while sabre-tooth Homotherium latidens and wild dog Lycaon lycaonoides were coursing predators in open habitat . The giant, short-faced hyena Pachycrocuta brevirostris scavenged the prey of these hypercarnivores.

Geographic variation in diets of ancient populations of 5-million-year-old (early Pliocene) horses from southern North America

Using tooth morphology and carbon isotopes, geographic differences in diets are presented for four species of early Pliocene horses (late Hemphillian, Hh 4, between 5.8 and 4.8 Ma) from four localities in Florida, Texas, and Mexico. These four species include three-toed Nannippus aztecus, Neohipparion eurystyle, and one-toed Astrohippus stockii, and Dinohippus mexicanus. The amount of dental variation represented in local populations of these extinct species is similar to that seen in extant equid populations (coefficients of variation, Vs, between ~ 4 and 10). As such, the fossil accumulations of individual species from single localities can be treated as paleopopulations. All four of these horses have high-crowned teeth (hypsodonty indices between 2.6 and 3.1) and the question is addressed how these closely-related species partitioned their available resources to minimize competition. Comparisons of tooth morphology indicate negligible geographic differences between paleopopulations of the same species. Therefore local differences in diets evolved within a context of stasis in tooth morphology. Carbon isotopes of fossil equid tooth enamel indicate that most of the populations and species studied here were primarily C4 grazers, although with some exceptions: Nannippus aztecus tends to be more negative, indicating a higher proportion (~ 20%, or sometimes greater) of C3 plants in its diet. A few individuals within the paleopopulations demonstrate relatively negative tooth enamel carbon isotope values (between ~ − 3 and − 10‰), indicating a diet with some, to predominantly, C3 plants. The sources of isotopic variation result from a variety of factors including latitudinal and seasonal differences in C4 and C3 grass availability, local microhabitat differences, and possibly migration patterns. For the most part these four species of early Pliocene horses have similar diets consisting of predominantly C4 grasses. They therefore differentiated their niches through other evolutionary and ecological strategies, possibly including body size and local habitat differences.

Hypsodonty in ungulates: an adaptation for grass consumption or for foraging in open habitat?

AbstractHypsodont (i.e. high‐crowned) teeth have been interpreted as an indicator of feeding preferences and habitat selection in ungulates. For this reason, the degree of hypsodonty has been used for estimating the diet of ancient taxa and in palaeoenvironmental reconstructions. The goal of this study is to elucidate the relative importance of grass consumption and open habitat foraging in the development of hypsodont teeth, using novel computer techniques of knowledge discovery applied to a dataset of 134 species of artiodactyls and perissodactyls distributed among thirteen families. The results obtained suggest that high‐crowned teeth represent an adaptation for feeding in an open habitat, although the minimum threshold of hypsodonty seems to increase with the relative length of the anterior part of the jaw. On the contrary, there is no direct relationship between the degree of hypsodonty and the percentage of grass consumed, except for the correspondence between grazing and dwelling in open habitats. A relatively wide muzzle evidences an adaptation for grass foraging in open and mixed habitats, but there are some non‐grazing species from a closed habitat that also show wide muzzles. Thus, the hypsodonty index, combined with the length of the anterior part of the jaw and the width of the muzzle, allows accurate inferences on the ecological preferences of extinct ungulates.

Neue Deutungen zur Systematik und Palaeoökologie der Dorn-Dürkhiem-1-Hipparionen (Ober-Miozän, Turolium [MN11]), Rheinhessen, Deutschland

The Turolian vertebrate locality of Dorn-Durkheim is situated near the city of Mainz, SW-Germany. The mammalian fauna is significantly younger than most other late Miocene Central European faunas that have yielded an equally rich assemblage of hipparion remains. The Dorn-Durkheim hipparion fauna consists of isolated teeth and postcranial skeletal elements. We use the Vallesian (MN9) samples ofHippotherium primigenium from Eppelsheim and Howenegg (Germany) as standards for comparison. Based on cheek tooth occlusal dimensions and continuous variables of the astragali, we identify two clusters of dental and postcranial specimens. We argue that these two clusters belong to two populations of hipparions that differ from one another principally in their body size. We further investigate the populations from Eppelsheim (EPhP), the total of all Dorn-Durkheim specimens (DDpPall) and the two sub-populations from Dorn-Durkheim (DDhPri and DDhPsm) with respect to their dietary preferences. For this we use the microwear and mesowear methods. The paleodietary signals for each sub-population are found to be quite different. The larger sized population of Dorn-Durkheim (DDhPri) was a mixed feeder, while the small sized population (DDhPsm) is interpreted to have been a dedicated browser. In addition, we redefine the calculation of indices of hypsodonty so that they are more appropriate to equine horses. In comparing the hypsodonty indices of the hipparion populations from Eppelsheim and the total of the Dorn-Durkheim specimens we find no differences in hypsodonty. In our comparison of Dorn-Durkheim metacarpal III’s (MC III’s) with MC III’ from other pertinent European localities, we find two MC III’s from Dorn-Durkheim to be similar to the Howenegg population ofH. primigenium. However, eight Dorn-Durkheim specimens differ from the Howenegg population in having a relatively expanded crista sagittalis and reduced lateral and medial condyles. The only complete Dorn-Durkheim MC III is relatively longer than the those from the Howenegg population. This leads us to conclude that the MC III morphology of the smaller sized sub-population from Dorn-Durkheim (DDhPsm) exhibits an adaptation for more cursorial locomotion than the Howenegg hipparions, while the larger sized sub-population ventured into less forested habitats and was less cursorial. Based on the peculiarities of metapodial build and of cheek tooth dimensions, we recognize the population DDhPsm from Dorn-Durkheim as belonging to a new species of hipparionine horse,Hippotherium kammerschmitti. New species:Cormohipparion n. sp.,Hippotherium kammerschmitti n. sp.

Paleoecological reconstruction of a lower Pleistocene large mammal community using biogeochemical (δ13C, δ15N, δ18O, Sr:Zn) and ecomorphological approaches

Abstract Ecomorphological and biogeochemical (trace element, and carbon, nitrogen, and oxygen isotope ratios) analyses have been used for determining the dietary niches and habitat preferences of large mammals from lower Pleistocene deposits at Venta Micena (Guadix-Baza Basin, Spain). The combination of these two approaches takes advantage of the strengths and overcome the weakness of both approaches. The range of δ13Ccollagen values for ungulate species indicates that C3 plants were dominant in the diet of these mammals. δ13Ccollagen values vary among ungulates: perissodactyls have the lowest values and bovids the highest ones, with cervids showing intermediate values. The hypsodonty index measured in lower molar teeth and the relative length of the lower premolar tooth row indicate that the horse, Equus altidens, was a grazing species, whereas the rhino, Stephanorhinus etruscus, was a mixed feeder in open habitats. The similar δ13Ccollagen values shown in both perissodactyls does not reflect differences...

DIETS OF EAST AFRICAN BOVIDAE BASED ON STABLE ISOTOPE ANALYSIS

Abstract We provide stable carbon isotope data from 37 species of African bovids to document dietary preferences for C3 browse (or fruits) or C4 grass. These data provide a quantitative measure of the fraction of C4 grass in bovid diets, can be applied on regional to local scales, can be derived from tooth enamel and hair or other tissues, and permit the diets of bovids to be considered in the context of a grazer–browser continuum. We recognize hypergrazers (>95% C4 grass), grazers (70–95% C4 grass), mixed feeders (>30% C4 grass and >30% C3 browse), browsers (70–95% C3 browse), and hyperbrowsers or frugivores (>95% C3 browse or fruit). Our results suggest that, of the extant East African Bovidae, impala (Aepyceros melampus), Thomson’s gazelle (Gazella thomsonii), and oribi (Ourebia ourebi) can be construed as mixed feeders. Dietary estimates based on stable isotope analysis are in broad agreement with other measures of diet such as hypsodonty index, mass relationships, and wear scratches on enamel.

Paleoecological reconstruction of a lower Pleistocene large mammal community using biogeochemical (δ13C, δ15N, δ18O, Sr:Zn) and ecomorphological approaches

Ecomorphological and biogeochemical (trace element, and carbon, nitrogen, and oxygen isotope ratios) analyses have been used for determining the dietary niches and habitat preferences of large mammals from lower Pleistocene deposits at Venta Micena (Guadix-Baza Basin, Spain). The combination of these two approaches takes advantage of the strengths and overcome the weakness of both approaches. The range of δ13Ccollagen values for ungulate species indicates that C3 plants were dominant in the diet of these mammals. δ13Ccollagen values vary among ungulates: perissodactyls have the lowest values and bovids the highest ones, with cervids showing intermediate values. The hypsodonty index measured in lower molar teeth and the relative length of the lower premolar tooth row indicate that the horse, Equus altidens, was a grazing species, whereas the rhino, Stephanorhinus etruscus, was a mixed feeder in open habitats. The similar δ13Ccollagen values shown in both perissodactyls does not reflect differences in feeding behavior with other ungulates, but rather a lower isotope enrichment factor in these monogastric herbivores than in ruminants, owing to their lower metabolic efficiency. The cervids Eucladoceros giulii and Dama sp. show low hypsodonty values, indicating that they were mixed feeders or browsers from forested habitats, an ecomorphologically based conclusion corroborated in the former by its low δ15Ncollagen content (canopy effect). Bovid species (Bovini aff. Leptobos, Soergelia minor, and Hemitragus albus) presumably inhabited open environments, according to their comparatively high hypsodonty and δ15Ncollagen values. Carnivore species (Homotherium latidens, Megantereon whitei, Pachycrocuta brevirostris, Canis falconeri, and Canis etruscus) exhibit higher δ15Ncollagen values than ungulates. These results record the isotopic enrichment expected with an increase in trophic level and are also supported by low bone Sr.Zn ratios. The elevated δ15Ncollagen value for a sample of Mammuthus meridionalis, which came from an individual with unfused epiphyses, confirms that it was a suckling animal. The δ15Ncollagen value of the scimitar-cat H. latidens is well above that obtained for the young individual of Mammuthus, which indicates that juvenile elephants were an important part of its diet. The hippo, Hippopotamus antiquus, yielded unexpectedly high δ15Ncollagen values, which suggest feeding on aquatic, non-N2-fixing plants. The high δ18Ohydroxyl values of bovids Hemitragus and Soergelia and of cervid Dama indicate that these ungulates obtained most of their water requirements from the vegetation. The megaherbivores and Eucladoceros exhibit the lowest δ18Ohydroxyl values, which suggest increased water dependence for them. Paleosynecological analysis was based on the relative abundance of species of large mammals from different ecological categories, determined by feeding behavior and locomotion types. The comparison of the frequencies of such categories in Venta Micena with those found in modern African communities indicates that the composition of the paleocommunity closely resembles those of savannas with tall grass and shrubs. The net above-ground primary productivity estimated for the on-crop biomass of the mammalian species preserved in the fossil assemblage also yields a figure congruent with that expected for an open environment.

A Comparative Test of Adaptive Explanations for Hypsodonty in Ungulates and Rodents

Hypsodonty has long been recognized as an adaptation for grazing: grazing is suggested to increase tooth wear due to endogenous (e.g., fiber, silica) and/or exogenous (e.g., dust, grit) properties of ingested food. However, it is unknown whether tooth crown height is correlated with the mastication of high fiber or silica in grasses, the ingestion of external abrasives, or both. Furthermore, comparative studies of hypsodonty have not explicitly taken into account phylogenetic biases due to shared ancestry in tooth morphology and/or feeding behavior. This study highlights the relationship between molar crown height and feeding habits in African ungulates and South American rodents when phylogenetic effects are controlled. Among ungulates, high hypsodonty indices are significantly associated with specific plant and foraging height preferences, while habitat and climate show no correlation with tooth crown height. For rodents, grass-eating species are significantly more hypsodont than frugivorous or folivorous species, and arboreal rodents are less hypsodont than terrestrial species. These results as well as those of a posteriori analyses controlling for aspects of the behavioral ecology (e.g., grass-eating, substrate preference) of the sample species confirm the role of both diet and grit in shaping the evolution of cheek tooth crown height in herbivorous mammals.