Dental microwear in the orthodentine of the Xenarthra (Mammalia) and its use in reconstructing the palaeodiet of extinct taxa: the case study of Nothrotheriops shastensis (Xenarthra,Tardigrada, Nothrotheriidae)

The utility of orthodentine microwear analysis as a proxy for dietary reconstruction in xenarthrans (tree sloths, armadillos) was quantitatively and statistically accessed via low‐magnification stereomicroscopy. Features such as number of scratches and pits, as well as presence of gouges, hypercoarse scratches, > four large pits, > four cross scratches, and fine, mixed or coarse scratch texture were recorded in 255 teeth from 20 extant xenarthran species. Feature patterns are consistent with scar formation through abrasional (tooth–food) and attritional (tooth–tooth) contact. Number of scratches is the most dietary diagnostic microwear variable for xenarthrans, with herbivorous sloths characterized by > ten scratches and nonherbivorous armadillos by < ten scratches. Discriminant function analysis differentiated arboreal folivores (sloths) and frugivore‐folivores (sloths) both from each other and from fossorial carnivore‐omnivores (armadillos) and insectivores (armadillos). Microwear patterns in carnivore‐omnivores and insectivores are difficult to distinguish between; armadillo microwear may reflect a fossorial lifestyle (grit consumption) rather than primary diet. Cabassous centralis is anomalous in its microwear signal relative to all other insectivores. To test the utility of orthodentine microwear analysis as an indicator of palaeodiet in extinct xenarthrans, microwear in the ground sloth Nothrotheriops shastensis was quantitatively and statistically compared to microwear in extant taxa. Microwear patterns in N. shastensis are most comparable to extant folivores based on scratch number and hierarchical cluster analysis. This strongly supports an herbivorous diet for N. shastensis that is corroborated by multiple independent lines of evidence. Thus, orthodentine microwear analysis can be used to reconstruct diet in extinct xenarthrans. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 156 , 201–222.     

Feeding Ecology in Oligocene Mylodontoid Sloths (Mammalia,Xenarthra) as Revealed by Orthodentine Microwear Analysis

Recently, dental microwear analysis has been successfully employed to xenarthran teeth. Here, we present new data on use wear features on 16 molariforms of Orophodon hapaloides and Octodontotherium grande. These taxa count among the earliest sloths and are known from the Deseadan SALMA (late Oligocene). Modern phylogenetic analyses classify Octodontotherium and Orophodon within Mylodontoidea with whom they share lobate cheek teeth with an outer layer of cementum and a thick layer of orthodentine. Similar target areas of 100μm² were analyzed on the orthodentine surface of each tooth by stereomicroscopic microwear and by SEM microwear. Results were unlike those of extant sloths (stereomicroscopic microwear: Bradypus, Choloepus) and published data from fossil sloths (SEM microwear: Acratocnus, Megalonyx, Megatherium, Thinobadistes); thus, both approaches independently indicate a different feeding ecology for the Oligocene taxa. The unique microwear results suggest that both taxa fed on plant material with low to moderate intrinsic toughness (foliage, twigs) but also proposes intake of tougher food items (e.g., seeds). Frequent gouging of the tooth surfaces can be explained by exogenous influence on microwear, such as possible intake of abrasive grit. We suggest an unspecialized herbivorous diet for Octodontotherium and Orophodon utilizing diverse food resources of their habitat. These interpretations support the reconstruction of (1) Deseadan environments as open habitats with spreading savannas/grasslands and (2) both taxa as wide-muzzled bulk feeders at ground level.     

Relief index of second mandibular molars is a correlate of diet among prosimian primates and other euarchontan mammals

This study describes and tests a new method of calculating a shape metric known as the relief index (RFI) on lower second molars of extant euarchontan mammals, including scandentians (treeshrews), dermopterans (flying lemurs), and prosimian primates (strepsirhines and tarsiers). RFI is the ratio of the tooth crown three-dimensional area to two-dimensional planar area. It essentially expresses hypsodonty and complexity of tooth shape. Like other measurements of complexity, RFI ignores taxon-specific features, such as certain cusps and crests, which are usually considered in more traditional studies of tooth function. Traditional statistical analyses of the study sample show that RFI distinguishes taxa with differing amounts of structural carbohydrates in their diets, with frugivore/gramnivores being significantly lower in RFI than omnivores, and insectivores/folivores being significantly higher in RFI than the other two. Information on absolute size, or body mass, is needed to reliably parse out insectivores and folivores; however, if the study sample is limited to Primates, RFI alone distinguishes many folivores (lower) from insectivores (higher). Finally, phylogenetically independent contrasts of RFI and dietary preference are strongly correlated with one another, indicating that variance in RFI is better explained by dietary diversity than phylogenetic affinity in this sample. Because of the accuracy and phylogenetic insensitivity of the RFI among Euarchonta, this method can be applied to fossil primates and stem-primates (plesiadapiforms) and used to elucidate and compare their dietary preferences. Such comparisons are important for developing a more detailed view of primate evolution.     

The Postcranial Musculoskeletal System of Xenarthrans: Insights from over Two Centuries of Research and Future Directions

Xenarthrans stand out among mammals for various reasons, one of them being their musculoskeletal postcranial specializations. Extant armadillos, anteaters, and sloths feature archetypical adaptations to digging and/or diverse arboreal lifestyles. Numerous extinct xenarthrans dramatically depart in size and morphology from their extant relatives, which has sparked functional interpretations since the end of the eighteenth century. Here, we review the diverse methodological approaches that have been used to investigate functional aspects of the postcranial musculoskeletal system in extant and extinct xenarthrans. Specifically, we address qualitative and quantitative bone morphology (including geometric morphometrics), body size and allometry, bone inner structure, myology, as well as in vivo, ex vivo, and in silico experimentation. Finally, a short account is given on those analyses that included xenarthrans to gain insight into primate anatomy. This review helped to identify potential future directions for the functional analysis of the xenarthran anatomy, a tradition over two centuries old.     

Collagen Sequence Analysis of the Extinct Giant Ground Sloths Lestodon and Megatherium

For over 200 years, fossils of bizarre extinct creatures have been described from the Americas that have ranged from giant ground sloths to the ‘native’ South American ungulates, groups of mammals that evolved in relative isolation on South America. Ground sloths belong to the South American xenarthrans, a group with modern although morphologically and ecologically very different representatives (anteaters, armadillos and sloths), which has been proposed to be one of the four main eutherian clades. Recently, proteomics analyses of bone collagen have recently been used to yield a molecular phylogeny for a range of mammals including the unusual ‘Malagasy aardvark’ shown to be most closely related to the afrotherian tenrecs, and the south American ungulates supporting their morphological association with condylarths. However, proteomics results generate partial sequence information that could impact upon the phylogenetic placement that has not been appropriately tested. For comparison, this paper examines the phylogenetic potential of proteomics-based sequencing through the analysis of collagen extracted from two extinct giant ground sloths, Lestodon and Megatherium. The ground sloths were placed as sister taxa to extant sloths, but with a closer relationship between Lestodon and the extant sloths than the basal Megatherium. These results highlight that proteomics methods could yield plausible phylogenies that share similarities with other methods, but have the potential to be more useful in fossils beyond the limits of ancient DNA survival.     

Body mass estimation in xenarthra: A predictive equation suitable for all quadrupedal terrestrial placentals?

The Magnorder Xenarthra includes strange extinct groups, like glyptodonts, similar to large armadillos, and ground sloths, terrestrial relatives of the extant tree sloths. They have created considerable paleobiological interest in the last decades; however, the ecology of most of these species is still controversial or unknown. The body mass estimation of extinct species has great importance for paleobiological reconstructions. The commonest way to estimate body mass from fossils is through linear regression. However, if the studied species does not have similar extant relatives, the allometric pattern described by the regression could differ from those shown by the extinct group. That is the case for glyptodonts and ground sloths. Thus, stepwise multiple regression were developed including extant xenarthrans (their taxonomic relatives) and ungulates (their size and ecological relatives). Cases were weighted to maximize the taxonomic evenness. Twenty‐eight equations were obtained. The distribution of the percent of prediction error (%PE) was analyzed between taxonomic groups (Perissodactyla, Artiodactyla, and Xenarthra) and size groups (0–20 kg, 20–300 kg, and more than 300 kg). To assess the predictive power of the functions, equations were applied to species not included in the regression development [test set cross validation, (TSCV)]. Only five equations had a homogeneous %PE between the aforementioned groups. These were applied to five extinct species. A mean body mass of 80 kg was estimated for Propalaehoplophorus australis (Cingulata: Glyptodontidae), 594 kg for Scelidotherium leptocephalum (Phyllophaga: Mylodontidae), and 3,550.7 kg for Lestodon armatus (Phyllophaga: Mylodontidae). The high scatter of the body mass estimations obtained for Catonyx tarijensis (Phyllophaga: Mylodontidae) and Thalassocnus natans (Phyllophaga: Megatheriidae), probably due to different specializations, prevented us from predicting its body mass. Surprisingly, although obtained from ungulates and xenarthrans, these five selected equations were also able to predict the body mass of species from groups as different as rodents, carnivores, hyracoideans, or tubulidentates. This result suggests the presence of a complex common allometric pattern for all quadrupedal placentals. J. Morphol., 2008. © 2008 Wiley‐Liss, Inc.     

Orientation of the lateral semicircular canal in Xenarthra and its links with head posture and phylogeny

The orientation of the semicircular canals of the inner ear in the skull of vertebrates is one of the determinants of the capacity of this system to detect a given rotational movement of the head. Past functional studies on the spatial orientation of the semicircular canals essentially focused on the lateral semicircular canal (LSC), which is supposedly held close to horizontal during rest and/or alert behaviors. However, they generally investigated this feature in only a few and distantly related taxa. Based on 3D‐models reconstructed from µCT‐scans of skulls, we examined the diversity of orientations of the LSC within one of the four major clades of placental mammals, that is, the superorder Xenarthra, with a data set that includes almost all extant genera and two extinct taxa. We observed a wide diversity of LSC orientations relative to the basicranium at both intraspecific and interspecific scales. The estimated phylogenetic imprint on the orientation of the LSC was significant but rather low within the superorder, though some phylogenetic conservatism was detected for armadillos that were characterized by a strongly tilted LSC. A convergence between extant suspensory sloths was also detected, both genera showing a weakly tilted LSC. Our preliminary analysis of usual head posture in extant xenarthrans based on photographs of living animals further revealed that the LSC orientation in armadillos is congruent with a strongly nose‐down head posture. It also portrayed a more complex situation for sloths and anteaters. Finally, we also demonstrate that the conformation of the cranial vault and nuchal crests as well as the orientation of the posterior part of the petrosal may covary with the LSC orientation in Xenarthra. Possible inferences for the head postures of extinct xenarthrans such as giant ground sloths are discussed in the light of these results.     

Molar microwear in extant small-bodied faunivorous mammals: An analysis of feature density and pit frequency

This study quantitatively examined molar microwear in nine species of extant small-bodied faunivorous primates and microchiropterans. Comparative analyses were performed within the food category faunivory, both between hard- and soft-object feeding faunivores and between primarily insectivorous and carnivorous taxa. Additionally, microwear in faunivores was compared to that reported in the literature for frugivorous and folivorous primates. The results indicated that although insectivores and carnivores could not be distinguished by microwear analyses, hard-object faunivores (i. e., those that primarily consume beetles or actively comminute bone) can be readily distinguished from soft-object faunivores (i. e., moth, caterpillar, or vertebrate flesh specialists). The hard-object faunivores consistently exhibited greater pit frequencies (in excess of 40%). Furthermore, comparisons of these microwear data on faunivorous mammals to previous work on frugivorous and folivorous primates (Teaford, 1988, pers. comm.; Teaford and Runestad, 1992, pers. comm.; Teaford and Walker: American Journal of Physical Anthropology 64:191–200, 1984) permitted three observations to be made. 1) Faunivores tend to have higher mean feature densities than either frugivores or folivores, although these differences are not consistently statistically distinct. 2) Faunifores and frugivores that feed on hard-objects have comparable mean pit frequencies. 3) Although it is impossible to distinguish faunivores and folivores on the basis of metric analysis of gross molar morphology, this distinction can be made on microwear criteria. Both hard- and soft-object faunivores exhibit much higher mean pit frequencies than primarily folivorous species. © 1993 Wiley-Liss, Inc.     

Evidence for dietary niche separation based on infraorbital foramen size variation among subfossil lemurs

The size of the infraorbital foramen (IOF) has been used in drawing both phylogenetic and ecological inferences regarding fossil taxa. Within the order Primates, frugivores have relatively larger IOFs than folivores or insectivores. This study uses relative IOF size in lemurs to test prior trophic inferences for subfossil lemurs and to explore the pattern of variation within and across lemur families. The IOFs of individuals belonging to 12 extinct lemur species were measured and compared to those of extant Malagasy strepsirhines. Observations matched expectations drawn from more traditional approaches (e.g. dental morphology and microwear, stable isotope analysis) remarkably well. We confirm that extinct lemurs belonging to the families Megaladapidae and Palaeopropithecidae were predominantly folivorous and that species belonging to the genus Pachylemur (Lemuridae) were frugivores. Very high values for relative IOF area in Archaeolemur support frugivory but are also consistent with omnivory, as certain omnivores use facial touch cues while feeding. These results provide additional evidence that the IOF can be used as an informative osteological feature in both phylogenetic and paleoecological interpretations of the fossil record.     

Phylogenetic relationships among sloths (Mammalia, Xenarthra, Tardigrada): the craniodental evidence

This study is undertaken in order to evaluate specific hypotheses of relationship among extant and extinct sloths (Mammalia, Xenarthra, Tardigrada). Questions of particular interest include the relationship among the three traditional family groupings of extinct ground sloths and the monophyletic or diphyletic origin of the two genera of extant tree sloths. A computer‐based cladistic investigation of the phylogenetic relationships among 33 sloth genera is performed based upon 286 osteological characteristics of the skull, lower jaw, dentition and hyoid arch. Characters are polarized via comparisons with the following successive outgroups, all members of the supraordinal grouping Edentata: the Vermilingua, or anteaters; the Cingulata, or armadillos and glyptodonts; the Palaeanodonta; and the Pholidota, or pangolins. The results of the analysis strongly corroborate the diphyly of living tree sloths, with the three‐toed sloth Bradypus positioned as the sister‐taxon to all other sloths, and the two‐toed sloth Choloepus allied with extinct members of the family Megalonychidae. These results imply that the split between the two extant sloth genera is ancient, dating back perhaps as much as 40 Myr, and that the similarities between the two taxa, including their suspensory locomotor habits, present one of the most dramatic examples of convergent evolution known among mammals. The monophyly of the three traditional ground sloth families Megatheriidae, Megalonychidae and Mylodontidae is confirmed in the present study, and the late Miocene–Pleistocene nothrotheres are shown to form a clade. It is suggested that this latter clade merits recognition as a distinct family‐level grouping, the family Nothrotheriidae. The monophyly of the Megatherioidea, a clade including members of the families Megatheriidae, Megalonychidae and Nothrotheriidae, is also supported. Within Megatherioidea, the families Nothrotheriidae and Megatheriidae form a monophyletic group called the Megatheria. The relationships within the families Megatheriidae and Mylodontidae are fully and consistently resolved, although the hypothesized scheme of relationships among the late Miocene to Pleistocene members of the mylodontid subfamily Mylodontinae differ strongly from any proposed by previous authors. Within the family Megalonychidae, Choloepus is allied to a monophyletic grouping of West Indian sloths, although the relationships within this clade are not fully resolved. © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society, 2004, 140 , 255–305.     

Advantages and Limitations in the Use of Extant Xenarthrans (Mammalia) as Morphological Models for Paleobiological Reconstruction

Extant species of Xenarthra represent a severely restricted sample of the total diversity achieved by the group. Given their shared history, the extant representatives of the three major groups of xenarthrans (Cingulata, Folivora, and Vermilingua) provide a valuable basis for paleobiological inference. However, many extinct taxa are morphologically so dissimilar from their extant relatives that they suggest very different ways of life. In these cases, extinct forms do not have modern models within the group and the application of a simplistic and strict approach can produce nonsensical reconstructions. In this contribution, we evaluate the limitations of the use of extant xenarthrans as morphological models for paleobiological reconstructions. A database of linear dimensions of the appendicular skeleton of extant and extinct xenarthrans and other mammals (marsupials, carnivorans, rodents, primates, perissodactyls, artiodactyls, and proboscideans) was constructed. Exploratory analyzes were performed on general morphometric similarity between existing and extinct xenarthrans (PCA) and the accuracy of body mass estimates of extinct xenarthrans based on their close relatives and other mammals (simple and multiple linear regressions) were tested. Extinct xenarthrans occupy similar relative positions in the morphospaces as extant mammals other than their closest relatives. Most allometric equations, particularly those based only on xenarthrans, produced remarkable underestimates. This can be explained by dimensional differences (up to four orders of magnitude) and shape differences between most of the extinct and extant xenarthrans. This does not invalidate actualism and the use of analogues, but suggests the need to apply other approaches, such as mechanics, that address form-function relationships but are not necessarily based on known biological comparators.     

Comparative anatomy and histology of xenarthran osteoderms

Reconstruction of soft tissues in fossil vertebrates is an enduring challenge for paleontologists. Because inferences must be based on evidence from hard tissues (typically bones or teeth), even the most complete fossils provide only limited information about certain organ systems. Osteoderms ("dermal armor") are integumentary bones with high fossilization potential that hold information about the anatomy of the skin in many extant and fossil amniotes. Their importance for functional morphology and phylogenetic research has recently been recognized, but studies have focused largely upon reptiles, in which osteoderms are most common. Among mammals, osteoderms occur only in members of the clade Xenarthra, which includes armadillos and their extinct relatives: glyptodonts, pampatheres, and, more distantly, ground sloths. Here, I present new information on the comparative morphology and histology of osteoderms and their associated soft tissues in 11 extant and fossil xenarthrans. Extinct mylodontid sloths possessed simple, isolated ossicles, the presence of which is likely plesiomorphic for Xenarthra. More highly derived osteoderms of glyptodonts, pampatheres, and armadillos feature complex articulations and surface ornamentation. Osteoderms of modern armadillos are physically associated with a variety of soft tissues, including nerve, muscle, gland, and connective tissue. In some cases, similar osteological features may be caused by two or more different tissue types, rendering soft-tissue inferences for fossil osteoderms equivocal. Certain osteological structures, however, are consistently associated with specific soft-tissue complexes and therefore represent a relatively robust foundation upon which to base soft-tissue reconstructions of extinct xenarthrans.     

Buccal dental microwear variability in extant African Hominoidea: taxonomy versus ecology

Buccal microwear patterns on teeth are good indicators of the abrasiveness of foodstuffs and have been used to trace the dietary habits of fossil species, including primates and hominids. However, few studies have addressed the variability of this microwear. The abrasiveness of dietary components depends not only on the hardness of the particles ingested, but also on the presence of dust and other exogenous elements introduced during food processing. These elements are responsible for the microwear typology observed on the enamel surfaces of primate teeth. Here we analyzed the variability of buccal microwear patterns in African Great Apes (Gorilla gorilla and Pan troglodytes), using tooth molds obtained from the original specimens held in several osteological collections. Our results suggest that ecological adaptations at subspecies or population level account for differences in microwear patterns, which are attributed to habitat and ecological conditions within populations rather than differences between species. The findings from studies on the variability of buccal dental microwear in extant species will contribute to a better understanding of extinct hominids’ diet and ecology.     

Dental microwear texture analysis: technical considerations

Dental microwear analysis is commonly used to infer aspects of diet in extinct primates. Conventional methods of microwear analysis have usually been limited to two-dimensional imaging studies using a scanning electron microscope and the identification of apparent individual features. These methods have proved time-consuming and prone to subjectivity and observer error. Here we describe a new methodological approach to microwear: dental microwear texture analysis, based on three-dimensional surface measurements taken using white-light confocal microscopy and scale-sensitive fractal analysis. Surface parameters for complexity, scale of maximum complexity, anisotropy, heterogeneity, and textural fill volume offer repeatable, quantitative characterizations of three-dimensional surfaces, free of observer measurement error. Some results are presented to illustrate how these parameters distinguish extant primates with different diets. In this case, microwear surfaces of Cebus apella and Lophocebus albigena, which consume some harder food items, have higher average values for complexity than do folivores or soft fruit eaters.     

The evolution of hyoid apparatus in Xenarthra (Mammalia: Eutheria)

The hyoid apparatus reflects aspects of the form and function of feeding in living and extinct organisms and, despite the availability of information about this structure for Xenarthra, it remains little explored from an evolutionary perspective. Here we compare the morphology of the hyoid apparatus in xenarthrans, describing its general morphology and variation in each major clade and score these variations as phylogenetic characters, which were submitted to ancestral states reconstructions. The general hyoid morphology of Xenarthra consists of a v-bone (basihyal fused with the thyrohyals) and three paired bones (stylohyal, epihyal and ceratohyal), which are unfused in the majority of taxa. The clade-specific morphology observed here, allowed us to obtain additional synapomorphies for all major clades of Xenarthra (Cingulata, Pilosa, Folivora and Vermilingua), for Glyptodontididae, and for Nothrotheriidae. The fusion of hyoid elements are convergentelly achieved among the diphyletic extant tree sloths, some extinct ground sloths and glyptodontids. Despite the heavy influence of adaptive evolution related to feeding habits, the morphology of the hyoid apparatus proved to be a valuable source of phylogenetic information.     

Similar Associations of Tooth Microwear and Morphology Indicate Similar Diet across Marsupial and Placental Mammals

Low-magnification microwear techniques have been used effectively to infer diets within many unrelated mammalian orders, but the extent to which patterns are comparable among such different groups, including long extinct mammal lineages, is unknown. Microwear patterns between ecologically equivalent placental and marsupial mammals are found to be statistically indistinguishable, indicating that microwear can be used to infer diet across the mammals. Microwear data were compared to body size and molar shearing crest length in order to develop a system to distinguish the diet of mammals. Insectivores and carnivores were difficult to distinguish from herbivores using microwear alone, but combining microwear data with body size estimates and tooth morphology provides robust dietary inferences. This approach is a powerful tool for dietary assessment of fossils from extinct lineages and from museum specimens of living species where field study would be difficult owing to the animal’s behavior, habitat, or conservation status.     

Retroposed elements and their flanking regions resolve the evolutionary history of xenarthran mammals (armadillos, anteaters, and sloths)

Armadillos, anteaters, and sloths (Order Xenarthra) comprise 1 of the 4 major clades of placental mammals. Isolated in South America from the other continental landmasses, xenarthrans diverged over a period of about 65 Myr, leaving more than 200 extinct genera and only 31 living species. The presence of both ancestral and highly derived anatomical features has made morphoanatomical analyses of the xenarthran evolutionary history difficult, and previous molecular analyses failed to resolve the relationships within armadillo subfamilies. We investigated the presence/absence patterns of retroposons from approximately 7,400 genomic loci, identifying 35 phylogenetically informative elements and an additional 39 informative rare genomic changes (RGCs). DAS-short interspersed elements (SINEs), previously described only in the Dasypus novemcinctus genome, were found in all living armadillo genera, including the previously unsampled Chlamyphorus, but were noticeably absent in sloths. The presence/absence patterns of the phylogenetically informative retroposed elements and other RGCs were then compared with data from the DNA sequences of the more than 12-kb flanking regions of these retroposons. Together, these data provide the first fully resolved genus tree of xenarthrans. Interestingly, multiple evidence supports the grouping of Chaetophractus and Zaedyus as a sister group to Euphractus within Euphractinae, an association that was not previously demonstrated. Also, flanking sequence analyses favor a close phylogenetic relationship between Cabassous and Tolypeutes within Tolypeutinae. Finally, the phylogenetic position of the subfamily Chlamyphorinae is resolved by the noncoding sequence data set as the sister group of Tolypeutinae. The data provide a stable phylogenetic framework for further evolutionary investigations of xenarthrans and important information for defining conservation priorities to save the diversity of one of the most curious groups of mammals.     

Relationships between dental microwear and diet in Carnivora (Mammalia) — Implications for the reconstruction of the diet of extinct taxa

Food consumption causes distinct microwear patterns on teeth, especially in mammals that actively masticate food. Here we perform a microwear analysis to assess the relationships between diet and microwear features of diverse Carnivora. Our database includes approximately 230 individuals of 17 extant species having different diets. We analyse both slicing and grinding facets of M1 and m1. The proposed method is reproducible and allows the differentiation, especially on slicing facets, of microwear poles that are significantly distinct from one another. In carnivorans, the microwear features mainly result from their foraging behavior and the proportion of certain food items consumed. We applied our method to extinct taxa such as the amphicyonid Amphicyon major. The results on the m1 slicing facet indicate dietary similarities between this large Miocene predator and the extant red fox; results from the m1 grinding facet do not have equivalent in extant taxa, however.     

An analysis of cercopithecoid odontometrics. I. The scaling of the maxillary dentition.

The relations between two tooth indices, post-canine area and incisor width in the upper jaw, and three variables, diet, body weight and body weight dimorphism, were examined separately for the males and females of 29 cercopithecoid species. Each species was assigned to one of three diet classes (folivore, frugivore, omnivore). Data on the other variable consisted of species means (log-transformed) obtained from published sources. The analytic techniques used were bivariate and multiple regression, the tooth indices being the dependent variables. All tooth indices scaled isometrically within diet classes, and all except female incisor width scaled with positive allometry across diet classes. In both sexes, the body weight adjusted mean incisor width of folivores was significantly smaller than that of either frugivores or omnivores. In the females, the body weight adjusted mean post-canine areas did not differ significantly across diet classes, while in the males the omnivores had a larger body weight adjusted mean post-canine area than either the folivores or frugivores. Female post-canine area was the only tooth index for which body weight dimorphism was a significant predictor. Extrapolations of these findings to other extant and to fossil primate species are discussed.     

The relationship between diet and tooth complexity in living dentigerous saurians

Living saurian reptiles exhibit a wide range of diets, from carnivores to strict herbivores. Previous research suggests that the tooth shape in some lizard clades correlates with diet, but this has not been tested using quantitative methods. I investigated the relationship between phenotypic tooth complexity and diet in living reptiles by examining the entire dentary tooth row in over 80 specimens comprising all major dentigerous saurian clades. I quantified dental complexity using orientation patch count rotated (OPCR), which discriminates diet in living and extinct mammals, where OPCR‐values increase with the proportion of dietary plant matter. OPCR was calculated from high‐resolution CT‐scans, and I standardized OPCR‐values by the total number of teeth to account for differences in tooth count across taxa. In contrast with extant mammals, there appears to be greater overlap in tooth complexity values across dietary groups because multicusped teeth characterize herbivores, omnivores, and insectivores, and because herbivorous skinks have relatively simple teeth. In particular, insectivorous lizards have dental complexities that are very similar to omnivores. Regardless, OPCR‐values for animals that consume significant amounts of plant material are higher than those of carnivores, with herbivores having the highest average dental complexity. These results suggest reptilian tooth complexity is related to diet, similar to extinct and extant mammals, although phylogenetic history also plays a measurable role in dental complexity. This has implications for extinct amniotes that display a dramatic range of tooth morphologies, many with no modern analogs, which inhibits detailed dietary reconstructions. These data demonstrate that OPCR, when combined with additional morphological data, has the potential to be used to reconstruct the diet of extinct amniotes. J. Morphol. 278:500–522, 2017. © 2017 Wiley Periodicals, Inc.