Cécile Blondel

Geology and palaeontology of the Upper Miocene Toros-Menalla hominid locality, Chad

All six known specimens of the early hominid Sahelanthropus tchadensis come from Toros-Menalla site 266 (TM 266), a single locality in the Djurab Desert, northern Chad, central Africa. Here we present a preliminary analysis of the palaeontological and palaeoecological context of these finds. The rich fauna from TM 266 includes a significant aquatic component such as fish, crocodiles and amphibious mammals, alongside animals associated with gallery forest and savannah, such as primates, rodents, elephants, equids and bovids. The fauna suggests a biochronological age between 6 and 7 million years. Taken together with the sedimentological evidence, the fauna suggests that S. tchadensis lived close to a lake, but not far from a sandy desert, perhaps the oldest record of desert conditions in the Neogene of northern central Africa.

A New Method of Dental Microwear Analysis: Application to Extant Primates and Ouranopithecus macedoniensis (Late Miocene of Greece)

Abstract This study presents a new, reliable method of dental microwear analysis, which is applied to one of the largest published primate databases and to a Miocene hominoid, Ouranopithecus macedoniensis. Phase I and phase II molar facets were considered. A strict protocol during the molding and casting steps enabled the capture of sharp photographs using light stereomicroscopy. A semi-automatic method allows the quantification of the microwear features on digitized photographs. Inter-specific analysis on extant primates enabled recognition of three clusters. Primates feeding on soft fruits and leaves and having a low incidence of pitting on molar facets constitute the first cluster. A second group composed of the three sub-species of Papio, differs from the others by a high incidence of pitting and scratching on both molar facets. This is related to the consumption of abrasive graminoids and hard items. Pan troglodytes troglodytes and Pongo pygmaeus have an intermediate microwear pattern and constitute a third group. Ouranopithecus macedoniensis is close in dental microwear pattern to the three sub-species of Papio. This suggests the importance of the consumption of hard and abrasive items. Intra-specific analysis of dental microwear variations within a population of Pongo pygmaeus reveals no significant differences related to sex and molar-wear stage. According to these results, this alternative method appears to be repeatable, and therefore reliable, for paleodiet characterization of fossil primates.

Predormancy omnivory in European cave bears evidenced by a dental microwear analysis of Ursus spelaeus from Goyet, Belgium

Previous morphological and isotopic studies indicate that Late Pleistocene cave bear (Ursus spelaeus) diet ranged from mostly vegetarian to omnivory or even carnivory. However, such analyses do not provide information on seasonal diets, and only provide an average record of diet. A dental microwear analysis of 43 young and adult individuals demonstrate that, during the predormancy period, cave bears from Goyet (Late Pleistocene, Belgium) were not strictly herbivorous, but had a mixed diet composed of hard items (e.g., possibly bone), invertebrates (e.g., insects), meat (ungulates, small vertebrates), and/or plant matter (hard mast, seeds, herbaceous vegetations, and fruits). Therefore, our results indicate that cave bears at Goyet were generalist omnivores during the predormancy period, which is consistent with current data on the dietary ecology of extant bears during this season. These data also raise questions about the ecological role and causes of the extinction of cave bears.

Untangling the environmental from the dietary: dust does not matter.

Both dust and silica phytoliths have been shown to contribute to reducing tooth volume during chewing. However, the way and the extent to which they individually contribute to tooth wear in natural conditions is unknown. There is still debate as to whether dental microwear represents a dietary or an environmental signal, with far-reaching implications on evolutionary mechanisms that promote dental phenotypes, such as molar hypsodonty in ruminants, molar lengthening in suids or enamel thickening in human ancestors. By combining controlled-food trials simulating natural conditions and dental microwear textural analysis on sheep, we show that the presence of dust on food items does not overwhelm the dietary signal. Our dataset explores variations in dental microwear textures between ewes fed on dust-free and dust-laden grass or browse fodders. Browsing diets with a dust supplement simulating Harmattan windswept environments contain more silica than dust-free grazing diets. Yet browsers given a dust supplement differ from dust-free grazers. Regardless of the presence or the absence of dust, sheep with different diets yield significantly different dental microwear textures. Dust appears a less significant determinant of dental microwear signatures than the intrinsic properties of ingested foods, implying that diet plays a critical role in driving the natural selection of dental innovations.

A new species of the genus Microbunodon (Anthracotheriidae, Artiodactyla) from the Miocene of Pakistan: genus revision, phylogenetic relationships and palaeobiogeography

Lihoreau, F., Blondel, C., Barry, J. & Brunet, M. (2004). A new species of the genus Microbunodon (Anthracotheriidae, Artiodactyla) from the Miocene of Pakistan: genus revision, phylogenetic relationships and palaeobiogeography. — Zoologica Scripta, 33, 97–115.

The Eocene–Oligocene ungulates from Western Europe and their environment

Abstract A survey of Paleogene ungulates from Western Europe is drawn up from the results of previous work on the ungulate lineages of this period and from new data on two groups particularly representative of the Oligocene ungulate fauna: the ruminants and the Cainotheriidae based on new material collected in localities of the Quercy Phosphorites. The history of ungulates from Western Europe at the Eocene–Oligocene transition is marked by different phases of extinction and origination related to environmental changes. In this perspective, the relative diversity of groups and the modifications of their tooth morphology, which reflect a diet change, resulting from vegetation modifications are analysed from the Early Eocene to the Late Oligocene. In Western Europe, the Late Eocene and the Early Oligocene was a period of transition with an important change in faunal and floral composition. The diversity analysis of ungulates suggests that the Grande Coupure is the result of gradual climatic and geographic events that occurred from the Middle Eocene (Mammalian Paleogene (MP)13/14 reference levels) to the Early Oligocene (MP 21/22 reference levels). During this period, it has been demonstrated that important adaptive changes occurred in the ungulate dental pattern (selenodonty in artiodactyls, semihypsodonty in perissodactyls), and appendicular skeleton (fusion of the cuboid and navicular bones of the tarsus in artiodactyls). These morphological modifications coincided with environmental changes that were less extreme than in North America.

Seeds, browse, and tooth wear: a sheep perspective.

Abstract While grazing as a selective factor towards hypsodont dentition on mammals has gained a lot of attention, the importance of fruits and seeds as fallback resources for many browsing ungulates has caught much less attention. Controlled‐food experiments, by reducing the dietary range, allow for a direct quantification of the effect of each type of items separately on enamel abrasion. We present the results of a dental microwear texture analysis on 40 ewes clustered into four different controlled diets: clover alone, and then three diets composed of clover together with either barley, corn, or chestnuts. Among the seed‐eating groups, only the barley one shows higher complexity than the seed‐free group. Canonical discriminant analysis is successful at correctly classifying the majority of clover‐ and seed‐fed ewes. Although this study focuses on diets which all fall within a single dietary category (browse), the groups show variations in dental microwear textures in relation with the presence and the type of seeds. More than a matter of seed size and hardness, a high amount of kernels ingested per day is found to be correlated with high complexity on enamel molar facets. This highlights the high variability of the physical properties of the foods falling under the browsing umbrella.

New Apterodontinae (Hyaenodontida) from the Eocene Locality of Dur At-Talah (Libya): Systematic, Paleoecological and Phylogenetical Implications

The African Hyaenodontida, mainly known from the Late Eocene and Early Oligocene Fayum depression in Egypt, show a very poor diversity in oldest Paleogene localities. Here we report new hyaenodontidans found in the late Middle Eocene deposits of Dur At-Talah (Central Libya), known to have recorded the earliest radiation of African anthropoids. The new hyaenodontidan remains are represented by dental and postcranial specimens comprising the historical material discovered by R.J.G. Savage in the last century and that of the recent Franco-Libyan campaigns. This material includes two apterodontines, in particular a subcomplete skeleton of Apterodon langebadreae nov. sp., bringing new postcranial elements to the fossil record of the genus Apterodon. Anatomical analysis of the postcranial remains of Dur At-Talah suggests a semi-aquatic lifestyle for Apterodon, a completely unusual locomotion pattern among hyaenodontidans. We also perform the first cladistic analysis of hyaenodontidans including apterodontines: Apterodon and Quasiapterodon appear close relatives to “hyainailourines”, in particular to the African Oligo-Miocene Metasinopa species. Apterodon langebadreae nov. sp. could be the most primitive species of the genus, confirming an African origin of the Apterodontinae and a further dispersion event to Europe before the early Oligocene. These data enhance our knowledge of early hyaenodontidan diversification into Africa and underline how crucial is the understanding of their evolutionary history for the improvement of Paleogene paleobiogeographic scenarii.

New hippotragini (Bovidae, Mammalia) from the Late Miocene of Toros-Menalla (Chad)

Abstract Until now, the pre-Pleistocene record of the bovid tribe Hippotragini was rather poor. Two new taxa are described from the late Miocene of Toros-Menalla in northern Chad, which yielded the earliest known hominid, Sahelanthropus tchadensis. Tchadotragus sudrei n.gen. n.sp. is known by complete skulls and numerous horn-cores. It has typical hippotragine features such as long slender, curved horn-cores, weak cranial flexure, large frontal sinus, and hippotragine-like dentition, and is here taken as a basal member of the tribe, branching before the divergence between Oryx-Praedamalis and Hippotragus s.l. Saheloryx solidus n.gen. n.sp. is less well-known; it differs mainly by the lack of sinus in the frontal and horn-cores, shorter horn-cores, and rounded brain-case, but it shares with Tchadotragus a large number of features that prompt us to classify it also at the base of the hippotragine tree, perhaps as the sister-taxon of Tchadotragus. No other African taxon looks like Saheloryx, and the only one similar to Tchadotragus is from Sahabi, Libya. The abundance of hippotragines sharply distinguishes Toros-Menalla from the East African late Miocene bovid faunas.

Three-dimensional dental microwear texture analysis and diet in extant Suidae (Mammalia: Cetartiodactyla)

Abstract We investigated the dietary differences among four extant suid genera using 3D dental microwear texture analysis on the enamel surfaces of molar shearing facets. We tested the differences among four taxa for four variables: complexity, anisotropy, and heterogeneity at two scales. This enabled us to distinguish omnivorous taxa (Sus scrofa and Potamochoerus sp.) from herbivorous ones (Phacochoerus africanus and Hylochoerus meinertzhageni) in terms of complexity. Heterogeneity likely distinguishes the suids displaying specialized diets (homogenous surfaces in the grazer Ph. africanus) from the more generalized suids (heterogeneous surfaces in the omnivorous S. scrofa and Potamochoerus sp., and mixed feeder herbivorous H. meinertzhageni). This study represents the first step toward a better comprehension of the diet and ecology of extant and fossil suids and also puts forward new hypotheses to be tested, especially on the effects of rootling behavior.