Tooth wear in captive wild ruminant species differs from that of free-ranging conspecifics

The mesowear method evaluates the wear patterns of herbivore cheek teeth by visually evaluating the facet development of the occlusal surfaces. It thus allows classification of most herbivorous ungulates into browsers, grazers or intermediate feeders, due to the fact that in grazers, tooth wear is characterized by a comparatively high degree of abrasion, most probably due to the presence of silicacious phytoliths in grasses, a higher amount of dust and grit adhering to their forage, or both. It has been suggested that excessive tooth wear could be a particularly limiting factor in the husbandry of captive large browsing species, and major tooth wear was demonstrated in captive as compared to free-ranging giraffe. If this increased tooth wear in captivity was an effect of feeding type and diets fed, then it would be expected that other browsing species are affected in a similar manner. In order to test this hypothesis, we investigated the dental mesowear pattern in captive individuals of 19 ruminant species and compared the results to data on free-ranging animals. Compared to free-ranging populations, captive browsers show a significantly more abrasion-dominated tooth wear signal. The reverse applies to captive grazers, which tend to show a less abrasion-dominated wear in captivity. Captive ruminants were generally more homogenous in their wear signature than free-ranging ruminants. If grit contamination in the natural habitat is a major cause of dental wear in grazers, then diets in captivity, although similar in botanical composition, most likely contain less abrasives due to feeding hygiene. If dental wear is one of the major factors limiting longevity, then captive grazers should achieve longer lifespans than both captive browsers and free-ranging grazers. In particular with respect to browsers, the results suggest that captive feeding regimes could be improved.     

Relationships between oral morphology and feeding style in the Ungulata: a phylogenetically controlled evaluation

In ungulates it is argued that specialization in the consumption of a particular type of food (feeding style) is reflected in morphological adaptations of the organs involved in the selection, processing and digestion of food. We analysed the differences in size and morphology of some oral traits that have been functionally related to food-selection ability (muzzle width, incisor-arcade shape, incisor shape), prehension of food (incisor protrusion), food comminution (molar occlusal surface area, hypsodonty (high-crowned molars)) and intake rate (incisor breadth) between ungulate species with different feeding styles (browser, mixed feeder, grazer). Grazers were characterized by large-body-size species. After controlling only for body mass, we found that grazers had wider muzzles and incisors, more-protruding incisors and more-bulky and higher-crowned molars than did mixed feeders and browsers. When the analyses took into account both body mass and phylogeny, only body mass and two out of the three hypsodonty indexes used remained significantly different between feeding styles. Browsers were smaller, on average, than mixed feeders and grazers, whilst grazers and mixed feeders did not differ in size. Also, browsers had shorter and less-bulky molars than did mixed feeders and grazers; the latter two feeding styles did not differ from each other in any of the hypsodonty indexes. We conclude that the adaptation to different dietary types in most of the oral traits studied is subsumed by the effects of body mass and the sharing of common ancestors. We hypothesize that differences in the ability to exploit different food resources primarily result from differences in body mass between species, and also discuss why hypsodonty characterizes feeding styles.     

Phylogenetic signal in tooth wear dietary niche proxies

In the absence of independent observational data, ecologists and paleoecologists use proxies for the Eltonian niches of species (i.e., the resource or dietary axes of the niche). Some dietary proxies exploit the fact that mammalian teeth experience wear during mastication, due to both tooth‐on‐tooth and food‐on‐tooth interactions. The distribution and types of wear detectible at micro‐ and macroscales are highly correlated with the resource preferences of individuals and, in turn, species. Because methods that quantify the distribution of tooth wear (i.e., analytical tooth wear methods) do so by direct observation of facets and marks on the teeth of individual animals, dietary inferences derived from them are thought to be independent of the clade to which individuals belong. However, an assumption of clade or phylogenetic independence when making species‐level dietary inferences may be misleading if phylogenetic niche conservatism is widespread among mammals. Herein, we test for phylogenetic signal in data from numerous analytical tooth wear studies, incorporating macrowear (i.e., mesowear) and microwear (i.e., low‐magnification microwear and dental microwear texture analysis). Using two measures of phylogenetic signal, heritability (H²) and Pagel's λ, we find that analytical tooth wear data are not independent of phylogeny and failing to account for such nonindependence leads to overestimation of discriminability among species with different dietary preferences. We suggest that morphological traits inherited from ancestral clades (e.g., tooth shape) influence the ways in which the teeth wear during mastication and constrain the foods individuals of a species can effectively exploit. We do not suggest that tooth wear is simply phylogeny in disguise; the tooth wear of individuals and species likely varies within some range that is set by morphological constraints. We therefore recommend the use of phylogenetic comparative methods in studies of mammalian tooth wear, whenever possible.     

Correlation of relative muzzle width and relative incisor width with dietary preference in ungulates

Qualitative observations suggest that grazing ungulates have relatively broader muzzles than browsing ones, and that grazers have incisors that are all of a similar size, as opposed to the large central and smaller lateral incisors seen in browsers. These differences may be correlated respectively with the need for grazing ungulates to maintain a large daily intake, or for browsing ungulates to forage selectively in a stand of vegetation. Quantitative examination of relative muzzle width and incisor width ratio in 95 species of living ungulates, correlated with seven different types of dietary preferences, substantiated these observations, although phylogenetic history may exhort a strong influence on morphological proportions. For example, equids have relatively narrower muzzles than grazing ruminants despite their less selective mode of feeding. The narrowest relative muzzle widths are not found in regular browsers, but in high level browsers and in mixed feeders in open habitats. Incisor width ratio can distinguish grazers from browsers, but can not be used to discriminate mixed feeders from other feeding types, and grazers appear to have incisors that are relatively broader overall than those of other dietary types, in correlation with their relatively broader muzzles.     

Dietary adaptations in an ungulate community from the late Pliocene of Greece

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.     

植食性哺乳动物牙齿磨痕分析方法简介及其在古食性恢复中的应用前景

通过研究古哺乳动物的食性来探讨哺乳动物演化与古生态环境变化之间的关系是目前古生物学研究领域的一个热点,而牙齿磨痕分析是恢复古食性和重建古生态环境的重要手段。牙齿磨痕(dental wear)分析包括微痕(microwear)分析和中痕(mesowear)分析,两种方法均强调食性与牙齿磨痕模式的严格对应,即不同食性的动物具有不同的牙齿磨痕特征模式。近年来,牙齿磨痕分析方法以其简单、快捷和高效等优点已被广泛应用于奇蹄类、偶蹄类、啮齿类、长鼻类和食肉类等哺乳动物的食性研究。但哺乳动物的食性和摄食习性比较复杂,很可能会影响微痕和中痕分析对食性的分辨率。所以,为了获得更加详细的古食性信息和更高的食性分辨率,一方面要对微痕和中痕分析方法进行改进,增添稳定并具有食性识别意义的观测变量,另一方面,需要同时结合微痕和中痕分析,从而获得更加全面的食性信息。虽然牙齿磨痕分析目前主要应用于植食性哺乳动物的食性研究,但其原理对哺乳动物的其它类群也是适用的,随着磨痕分析方法的不断改进和其它类群磨痕数据库的建立,未来的牙齿磨痕分析将可以恢复更多类群的古食性,从而可以更加全面和准确地揭示古食性与古环境信息。     

Microwear evidence for Plio-Pleistocene bovid diets from Makapansgat Limeworks Cave, South Africa

Makapansgat Limeworks Cave is a well-known Australopithecus africanus bearing locality that has spawned a considerable amount of paleoecological research because of its hominin component. Most recently, the paleoecology of this Plio-Pleistocene site has been studied by determining the diet and habitat of other extinct taxa, particularly the bovids. The diets of seven bovids (Aepyceros sp., Gazella vanhoepeni, Makapania broomi, Parmularius braini, Redunca darti, Tragelaphus sp. aff. T. angasii, and Tragelaphus pricei) have now been classified using taxonomic uniformitarianism, ecomorphology, stable carbon isotopes, and mesowear analysis. Here, dental microwear is applied to the same bovids for additional comparison and to further elucidate the strengths and weaknesses of each method. The different dietary proxy methods noted provide a temporal continuum, with genetic signals such as ecomorphology and taxonomic uniformitarianism indicating behavioral adaptations over geologic time, while nongenetic data such as stable carbon isotopes and mesowear reflect different aspects of average diet over extended portions of an animal's life, and dental microwear provides dietary snapshots.Microwear separated an extant baseline of ten bovid species into expected dietary categories and the Makapansgat bovids clearly fell into two groups with the same degree of separation as between extant grazers and browsers. The results indicate that a multidisciplinary approach produces a more accurate and robust reconstruction of past diets. In sum, the microwear analysis is in-line with the isotope and mesowear results, which suggest a stronger browsing component than either taxonomic uniformitarianism or ecomorphology imply.     

Coevolution of Tooth Crown Height and Diet in Oreodonts (Merycoidodontidae, Artiodactyla) Examined with Phylogenetically Independent Contrasts

The evolution of increased tooth crown height is considered to be an adaptation for coping with excessive rates of dental wear associated with abrasive herbivorous diets, such as grazing and(or high levels of exogenous grit (e.g. dust, sand, ash). Evolutionary trends in the crown heights of North American ungulates are grossly consistent with a transition from closed forests in the early Eocene to open grasslands in the late Miocene. However, the evolutionary proliferation of hypsodonty (high crowned teeth) in the early and middle Miocene occurs later than the apparent origin of open grassland habitats in North America. The paleoecology of species from the interval between the appearance of grasslands and the evolutionary proliferation of hypsodonty is critical to understanding the role of Cenozoic climate change in mammalian evolution. The paleodiets of late Eocene to middle Miocene oreodonts (Merycoidodontidae) were reconstructed by examining the relative facet development of molars (mesowear). A two-phase diet trend was discovered. Phase 1 suggests either an average reduction in the amount of exogenous grit from the late Eocene to early Oligocene or a decrease in fruit consumption related to the disappearance of more wooded habitats. Phase 2 is a gradual transition from early Oligocene low-abrasion browsing to high abrasion diets similar to mixed feeding and grazing in the Miocene. According to mesowear data, oreodont diets similar to those of modern grazers in terms of abrasion are not seen until the early Miocene (early Hemingfordian land mammal age). The coevolutionary relationship of molar crown height and diet, as represented by mesowear, was examined using phylogenetically independent contrasts. No significant coevolutionary relationship was found. In several instances, diet was found to shift over time despite morphological stasis (i.e. within a single species). These results do not clearly indicate that the overall trend of increasing dietary abrasion imposed sufficient selection to drive crown height evolution in oreodonts. Therefore, direct fossil evidence of dietary abrasion as a causal factor in the evolution of crown height, at least in this clade, is elusive.     

THE SHAPE OF CONTENTION: ADAPTATION,HISTORY, AND CONTINGENCY IN UNGULATE MANDIBLES

Mandibles and teeth of ungulates have been extensively studied to discern the functional significance of their design. Grazing ungulates have deeper mandibles, longer coronoid processes, flatter incisor arcades, and more hypsodont molars in comparison to browsers. If the functional significance of both mandible and teeth shapes is well‐established, it remains uncertain to what extent mandible shapes are really adapted to grazing, meaning that they evolved either to serve their current biological function or just as a structural requirement to accommodate higher crowned molars. Here, we address this question by studying the contribution of phylogeny, hypsodonty, and body size to mandibular shape variation. The mandible shape appeared to be significantly influenced by hypsodonty but not by body size. Interestingly, hypsodonty‐related changes influenced the tooth row in artiodactyls and perissodactyls significantly but in the opposite directions, which is ultimately related to their different digestive strategies. Yet, we obtained a strong phylogenetic effect in perissodactyls, suggesting that their mandible shape should be strongly inherited. The strength of this effect was not significant within artiodactyls (where hypsodonty explained much more variance in mandible shape). Digestive strategy is deemed to interplay with hypsodonty to produce different paths of adaptation to particular diets in ungulates.     

New methods of tooth microwear analysis and application to dietary determination of two extinct antelopes

A separation exists between the tooth microwear of extant ruminant browsers and grazers when examined with new statistical techniques such as the dichotomous, polychotomous and continuous methods. Extant mixed feeders, however, could not be discerned as a distinct group. Many variables were used in the analysis, including two new variables; the area and perimeter of scars.A standard definition of a pit is deduced and a recommendation is made for a method and a model which best charactrizes the enamel scars for determination of browsing and grazing dietary categories. The best diagnostic method of tooth microwear analysis utilizes the number of pits smaller than or equal to the ratio four (lenth over width), the number of scratches between four and 100 micrometres in length to width ratio, and the number of gouges greater than 100 micrometres in length to width ratio. Browsers have many pits and few scratches, with the exception of the giraffe. Grazers have many scratches and few pits, with the exception of the common waterbuck.
The tooth microwear analysis suggests that Tragoportax amalthea (Boselaphini, Bovidae) was a mixed feeder at Pikermi and a grazer at Samos. Using the dietary adaptations and the time differences (Pikermi is slightly older than Samos), it is assumed that we ahve recorded evolutionary change from a mixed feeder to a grazer. Tragoportax rugosifrons from Samos was a grazer. Pikermi and Samos are Miocene (Turolian) localities in Greece.     

Tooth microwear and premaxillary shape of an archaic antelope

Extant ungulates can be divided into three dietary categories: browsing feeders, grazing feeders, and mixed feeders. Dietary adaptations can be differentiated in extinct ruminants based upon tooth microwear analysis as well as evaluation of premaxillary morphology. Tooth microwear shows that the extinct bovid Kipsigicerus labidotus from the Miocene of Fort Ternan in Kenya (14 million years old) was most likely a grazing feeder, with mixed-feeder tendencies, while morphologically the premaxilla most closely resembles that of a mixed feeder. Because the paleoenvironment at Fort Ternan was likely to have been forested, as shown by paleosol isotopic studies, grazing in this particular ruminant evolved within a forested environment preceding the origin of savanna. □ Tooth microwear, premaxilla, Miocene, Kenya, bovid, paleodiet.     

On the relationship between hypsodonty and feeding ecology in ungulate mammals,and its utility in palaeoecology

High‐crowned (hypsodont) teeth are widely found among both extant and extinct mammalian herbivores. Extant grazing ungulates (hoofed mammals) have hypsodont teeth (a derived condition), and so extinct hypsodont forms have usually been presumed to have been grazers. Thus, hypsodonty among ungulates has, over the past 150 years, formed the basis of widespread palaeoecological interpretations, and has figured prominently in the evolutionary study of the spread of grasslands in the mid Cenozoic. However, perceived inconsistencies between levels of hypsodonty and dental wear patterns in both extant and extinct ungulates have caused some workers to reject hypsodonty as a useful predictive tool in palaeobiology, a view that we consider both misguided and premature. Despite the acknowledged association between grazing and hypsodonty, the quantitative relationship of hypsodonty to the known ecology of living ungulate species, critical in making interpretations of the fossil record, was little studied until the past two decades. Also, much of the literature on ungulate ecology relevant to understanding hypsodonty has yet to be fully incorporated into the perspectives of palaeontologists. Here we review the history and current state of our knowledge of the relationship between hypsodonty and ungulate ecology, and reassert the value of hypsodonty for our understanding of ungulate feeding behaviour. We also show how soil consumption, rather than the consumption of grass plants per se, may be the missing piece of the puzzle in understanding the observed correlation between diets, habitats, and hypsodonty in ungulates. Additionally, we show how hypsodonty may impact life‐history strategies, and resolve some controversies regarding the relevance of hypsodonty to the prediction of the diets of extinct species. This in turn strengthens the utility of hypsodonty in the determination of past environmental conditions, and we provide a revised view of a traditional example of evolutionary trends in palaeobiology, that of the evolution of hypsodonty in horses and its correlation with the Miocene spread of grasslands in North America.     

Differences in Tooth Microwear of Populations of Caribou (<Emphasis Type="Italic">Rangifer tarandus</Emphasis>, Ruminantia,Mammalia) and Implications to Ecology,Migration, Glaciations and Dental Evolution

Tooth microwear was analyzed for a large sample of wild-shot barren-ground caribou (Rangifer tarandus groenlandicus) from the Kaminuriak population of eastern Canada. This sample was compared to the microwear of specimens from three Pleistocene localities in North America (Alaska) and western Europe (Caune de l’Arago in France and Salzgitter in Germany). The results show that the extant samples from eastern Canada have seasonal variation in microwear and presumably in diet. The differences in microwear between the various seasons may reflect a cyclic migration of the population within a year. The extinct population from Alaska has extremely blunt teeth (mesowear), as blunt as those of modern zebras and bison. This observation is corroborated by the lowest number of microwear pits. The findings are untypical, as most typical caribou teeth have sharper apices, and we interpret this as an indication of a local habitat that was different with animals feeding on non-typical vegetation. The combination of Rangifer from Caune de l’Arago and Salzgitter reveals a pattern in microwear variability. The Salzgitter is interglacial and shows a greater diversity of browsing (broad spectrum on average number of pits) than the glacial Caune de l’Arago. The interglacial population from Salzgitter is interesting because it shows several different types of browsing. Collectively all the Rangifer teeth show that diet of a brachydont taxon can vary across most of the dietary morphospace of ungulates as represented by tooth microwear. The three Pleistocene samples exhibit microwear that is different from the extant population in question. This observation implies that the recent diet of Rangifer has changed from the typical caribou diet in the past. This indicates dietary change within a species. This is important because it represents dietary evolution without changes in tooth morphology.     

Detecting Inter-Cusp and Inter-Tooth Wear Patterns in Rhinocerotids

Extant rhinos are the largest extant herbivores exhibiting dietary specialisations for both browse and grass. However, the adaptive value of the wear-induced tooth morphology in rhinos has not been widely studied, and data on individual cusp and tooth positions have rarely been published. We evaluated upper cheek dentition of browsing Diceros bicornis and Rhinoceros sondaicus, mixed-feeding R. unicornis and grazing Ceratotherium simum using an extended mesowear method adapted for rhinos. We included single cusp scoring (EM(R)-S) to investigate inter-cusp and inter-tooth wear patterns. In accordance with previous reports, general mesowear patterns in D. bicornis and R. sondaicus were attrition-dominated and C. simum abrasion-dominated, reflecting their respective diets. Mesowear patterns for R. unicornis were more attrition-dominated than anticipated by the grass-dominated diet, which may indicate a low intake of environmental abrasives. EM(R)-S increased differentiation power compared to classical mesowear, with significant inter-cusp and inter-tooth differences detected. In D. bicornis, the anterior cusp was consistently more abrasion-dominated than the posterior. Wear differences in cusp position may relate to morphological adaptations to dietary regimes. Heterogeneous occlusal surfaces may facilitate the comminution of heterogeneous browse, whereas uniform, broad grinding surfaces may enhance the comminution of physically more homogeneous grass. A negative tooth wear gradient was found in D. bicornis, R. sondaicus and R. unicornis, with wear patterns becoming less abrasion-dominated from premolars to molars. No such gradients were evident in C. simum which displayed a uniform wear pattern. In browsers, premolars may be exposed to higher relative grit loads, which may result in the development of wear gradients. The second premolar may also have a role in food cropping. In grazers, high absolute amounts of ingested abrasives may override other signals, leading to a uniform wear pattern and dental function along the tooth row, which could relate to the observed evolution towards homodonty.     

Phylogenetic topology mapped onto dietary ecospace reveals multiple pathways in the evolution of the herbivorous niche in African Bovidae

Understanding the evolutionary history of the herbivore niche within African bovids has traditionally relied on examining anatomical adaptations to diet, particularly those related to digestive strategy. More recently, mesowear and stable isotope analyses have been used to great effect to reconstruct dietary preferences. We use these dietary proxies to construct a morphology‐free dietary ecospace and examine the topology of the phylogenetic relationships of African bovids mapped onto this ecospace. The reconstructed dietary ecospace provides evidence for four distinct dietary classes: species with C3‐ or C4‐dominated diets that produce low or high occlusal relief, likely related to diets high or low in abrasives, respectively. We detected no evidence for a discrete mixed feeder category; the species often categorized as such represent the end members of groups of species with either C3‐ or C4‐ dominated diets. Our analysis reveals high variability within the C4 grazing ecospace, and phylogenetic evidence indicates at least two pathways to grazing, likely related to the abrasive qualities of ingested food, which may be determined by the moisture content or the height of consumed grasses. These different pathways probably contribute to the high diversity of African grazers, both today and in the fossil record. C3 browsers (non‐frugivores) also display a high degree of variation, but there are no species associated with highly abrasive diets and there is evidence for only a single evolutionary pathway. We find evidence for only one evolutionary route towards frugivory, which includes species with diets that produce both high and low occlusal reliefs. The cause of abrasive wear in frugivores may be related to grit and/or the hard parts of fruits, but this requires further examination.     

Dental microwear variability on buccal tooth enamel surfaces of extant Catarrhini and the Miocene fossil Dryopithecus laietanus (Hominoidea)

Analyses of buccal tooth microwear have been used to trace dietary habits of modern hunter-gatherer populations. In these populations, the average density and length of striations on the buccal surfaces of teeth are significantly cor-related with the abrasive potential of food items consumed. In non-human pri-mates, tooth microwear patterns on both occlusal and buccal wear facets have been thoroughly studied and the results applied to the characterization of dietary habits of fossil species. In this paper, we present inter- and intra-specific buccal microwear variability analyses in extant Cercopithecoidea (Cercopithecus mitis, C. neglectus, Chlorocebus aethiops, Colobus spp., Papio anubis) and Hominoidea (Gorilla gorilla, Pan troglodytes, Pongo pygmaeus). The results are tentatively compared to buccal microwear patterns of the Miocene fossils Dryopithecus and Oreopithecus. Significant differences in striation density and length are found among the fossil taxa studied and the extant primates, suggesting that buccal microwear can be used to identify dietary differences among taxa. The Dryopithecus buccal microwear pattern most closely resembles that of abrasive, tough plant foods consumers, such as the gorilla, in contrast to stud-ies of dental morphology that suggest a softer, frugivorous diet. Results for Oreopithecus were equivocal, but suggest a more abrasive diet than that previously thought.     

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

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Palaeoecology of cave bears as evidenced by dental wear analysis: a review of methods and recent findings

Abstract

The study of dental wear was first used years ago to infer the palaeoecology of fossil mammals and in particular their diet. Results depend predominantly on the scale of the analysis used. Analyses of dental macrowear, mesowear or microwear do not provide the same type of dietary information, be it about the seasonal, annual or lifetime diet. This contribution focuses on emblematic species, cave bears (Ursidae), in particular Ursus spelaeus spelaeus. Methods used by previous researchers to infer their dietary preferences and thus their palaeoecology are reviewed and compared. This review is complemented by an analysis of several specimens of cave bears from the Goyet cave in Belgium, using dental microwear texture analysis (DMTA), a methodology widely applied for reconstructing palaeodiets. Three main conclusions are drawn here: (1) DMTA is the method that provides the most precise palaeobiological inferences; (2) during the pre-dormancy period, cave bears show dietary flexibility; (3) dental wear alone might be not sufficient to provide a complete reconstruction of the cave bear palaeodiet.     

Seasonal Mortality Patterns in Primates: Implications for the Interpretation of Dental Microwear

The microscopic traces of use wear on teeth have been extensively studied to provide information that will assist in elucidating the dietary habits of extinct hominin species. 1 - 13 It has been amply documented that dental microwear provides information pertaining to diet for living animals, where there is a strong and consistent association between dental microwear patterns and different types of foods that are chewed. The details of occlusal surface wear patterns are capable of distinguishing among diets when the constituent food items differ in their fracture properties. 14 - 20 For example, the microwear traces left on the teeth of mammals that crush hard, brittle foods such as nuts are generally dominated by pits, whereas traces left on the teeth of mammals that shear tough items such as leaves tend to be characterized by scratches. These microwear features result from and thus record actual chewing events. As such, microwear patterns are expected to be variably ephemeral, as individual features are worn away and replaced or overprinted by others as the tooth wears down in subsequent bouts of mastication. Indeed, it has been demonstrated, both in the laboratory and the wild, that short‐term dietary variation can result in the turnover of microwear. 17 , 21 - 23 Because occlusal microwear potentially reflects an individual's diet for a short time (days, weeks, or months, depending on the nature of the foods being masticated), tooth surfaces sampled at different times will display differences that relate to temporal (for example, seasonal) differences in diet. 24     

The diet of <Emphasis Type="Italic">Metaschizotherium bavaricum</Emphasis> (Chalicotheriidae,Mammalia) from the MN 5 of Sandelzhausen (Germany) implied by the mesowear method

The genus Metaschizotherium is a Miocene member of the Schizotheriinae (Chalicotheriidae, Perissodactyla) and appears in the MN 5 of Southern Germany with the species M. bavaricum. The Chalicotheriidae have mostly been reconstructed as browsers. In this study, the mesowear method is applied to 11 upper premolars and molars of M. bavaricum from the Upper Freshwater Molasse locality of Sandelzhausen (MN 5). With this method the amount of abrasive and attritive dental wear is investigated and thus it provides a time-averaged signature of food abrasiveness of ungulates. Principal components analysis is performed on mesowear variables of M. bavaricum. This species is found to classify closest to extant mixed feeding ruminants. This indicates that the diet of M. bavaricum essentially included nonabrasive browse but also a certain amount of abrasive plant material. The composition of the diet of extant reference species indicates that this abrasiveness was most likely imposed by bark and whole branches. In the palaeoecological context of Sandelzhausen M. bavaricum occupied the dietary niche of a mixed feeder or an abrasion-dominated browser. A high degree of similarity is recognised between the mesowear patterns of M. bavaricum from Sandelzhausen and M. fraasi from the MN 6 of the Franconian Alb. This is interpreted as reflecting a similar dietary niche of the two species.