Skills and Expertise
Ecology and EvolutionEvolutionTaxonomyBiodiversity & ConservationSystematicsPhylogenetic AnalysisPhylogeneticsEvolutionary BiologyPhylogenyOsteologyAnatomyPaleontologyComparative AnatomyBiogeographyFossilsFunctional MorphologyVertebrate PaleontologyCladisticsVertebratesBone ResearchMacroevolutionPaleobiology
Apr 2004 - Aug 2006
University of N'Djamena
- scientific expert
The PaleoSen project is an international collaborative framework aiming to discover, study, and preserve the Senegalese paleontological heritage. More specifically, we seek to document the evolution of the marine and continental vertebrate faunas from the end of the Mesozoic to the beginning of the Cenozoic period. To this end, the PaleoSen project aims to: - prospect the numerous unexplored regions of Senegal; - organise excavations in recently discovered sites; - study and publish the newly discovered fossil material; - contribute to the formation of new Senegale scientists; - initiate the formation of the first palaeontology collection in the Department of Geology in Dakar in order to provide access and care for the fossil material to local scientists, students, and scientific visitors. For more information, visit our website: www.paleosen.com
Research Item (65)
- Jun 2017
The Hippopotamidae have been a major component of the African wetland fauna for the last 7 million years, following the ‘Hippopotamine Event,’ i.e., the sudden emergence in the fossil record of the subfamily Hippopotaminae, including both extant species. The general dearth of African fossiliferous deposits dated between 9.5 Ma and 7.5 Ma concealed until now the evolution that led to the Hippopotamine Event and the subsequent success of these large semiaquatic herbivores. Part of this evolution is unveiled by the hippopotamid dental remains found at Chorora, a late Miocene site of the southern Afar Depression in Ethiopia spanning most of the fossil-depleted time interval. Although fragmentary, these remains represent a new, mid-sized hippopotamid species dated to ca. 8 Ma, as well as a somewhat younger, larger form. A cladistic analysis of a large array of cetartiodactyls indicates that the Chorora taxa were basal to the latest Miocene hippopotamines. The new species displays a mosaic of dental characters that support the attribution of the new species to a new genus within Hippopotaminae. The new fossils also clarify the course of early hippopotamine dental evolution. The Chorora hippopotamids suggest that transition to a marked abundance of hippopotamines with their unique dental pattern in African ecosystems occurred within a relatively short time interval, most probably between 8 Ma and 7.5 Ma. http://zoobank.org/urn:lsid:zoobank.org:pub:47B9381F-E3B5-40C9-B9AB-51CC3D0D3A8A SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP Citation for this article: Boisserie, J.-R., G. Suwa, B. Asfaw, F. Lihoreau, R. L. Bernor, S. Katoh, and Y. Beyene. 2017. Basal hippopotamines from the upper Miocene of Chorora, Ethiopia. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1297718.
We describe here an ichthyological and herpetological assemblage that was obtained from washing-screening sediments from the early late Oligocene locality of Lokone, Kenya. This provides original information on the hitherto oldest known fauna from the East African Rift since it started to open from north to south during the Oligocene. The description of the fossil remains allows the identification of crocodiles (crocodylids), squamates (lacertid and Serpentes), turtles (pelomedusoids cf. Erymnochelys group), dipnoan (?Protopterus sp.), and actinopterygian fishes (Polypterus sp., Heterotis sp., Gymnarchus sp., Hydrocynus sp., Sindacharax sp. and other alestids, a claroteid, a cichlid, possibly a Distichodus, and other indeterminate fish). The preservation of this material testifies to a certain level of hydrodynamism, and the ecology of these ectotherm vertebrates suggests that freshwater environment was developed in this area. Moreover, the assemblage corresponds to herpeto- and ichthyofaunas that prefigured the modern African diversity as early as the Oligocene, before the Miocene invasion by Asian fish. It thus testifies to connections between the newly formed hydrographical system in the Turkana Basin with the Lokone main hydrographical system beginning at a very early stage of the Eastern Rift development. Citation for this article: Otero, O., G. Garcia, X. Valentin, F. Lihoreau, F. K. Manthi, and S. Ducrocq. 2017. A glimpse at the ectotherms of the earliest fauna from the East African Rift (Lokone, late Oligocene of Kenya). Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1312691.
- May 2017
Anoplotheriinae are Paleogene European artiodactyls that present a unique postcranial morphology with a tridactyl autopodium and uncommon limb orientation. This peculiar morphology led to various hypotheses regarding anoplotheriine locomotion from semiaquatic to partly arboreal or partly bipedal. The petrosal bone, housing the organs of balance, and hearing, offers complementary information to postcranial morphology on the ecology of this uncommon artiodactyl. Here, we investigate the middle ear and bony labyrinth of the small anoplotheriine Diplobune minor based on four specimens from the Early Oligocene locality of Itardies (Quercy, France). A macroscopic study coupled with a μCT scan investigation of the petrosal anatomy provides novel information on the bony labyrinth, stapes, and innervation and vasculature of the inner ear of this enigmatic taxon. The petrosal of D. minor exhibits a mosaic of plesiomorphic characters and peculiar features that shed new light into the anatomy of this poorly studied taxon of an obscure taxonomic clade. We can confidently reject that D. minor was a semiaquatic species based on the petrosal morphology: presence of a large mastoid process and nonpachyostotic tegmen tympani do not support underwater hearing. On the other hand, the average semicircular canal radius points to a slow or medium slow agility for D. minor, and fully rejects it was a fast moving animal, which is congruent with its postcranial anatomy.
We present new material of the selenodont anthracothere Hemimeryx blanfordi from the Oligocene deposits of the Bugti Hills (Balochistan, Pakistan), collected between 1999 and 2002. This is the first undisputed Oligocene occurrence of the species, previously known from the early Miocene of Pakistan. Investigation of the molar enamel microstructure reveals a surprising mono-zonal Schmelzmuster, already detected in some middle to Late miocene selenedont anthracotheres. We include this observation combined with a morphological revision of H. blanfordi and a cladistic assessment of the dental evidence, to propose a new phylogenetic hypothesis regarding Hemimeryx and its close relatives. We confirm the clade including advanced bothriodontines, which we erect to a tribe rank and name Merycopotamini. The South Asian origin of Merycopotamini is consistent with hypothesized subsequent dispersal events of Merycopotamini from Asia to Africa.
- Mar 2017
We describe five new specimens of Hippopotamidae from the Miocene of Napudet, a new site in southwestern Turkana Basin, Kenya. These specimens include fragmentary maxillae with teeth and a well-preserved mandibular symphysis. We attribute them to Kenyapotamus ternani, the least known species within Kenyapotamus, on the basis of relatively small dental dimensions and a clear distinction between the parastyle and the mesiostyle on the upper molars. This attribution suggests an age older than 10 Ma for Napudet. A cladistic analysis integrating these new data makes it possible to evaluate the relationships between middle Miocene hippopotamids and later representatives. The mandibular symphysis from Napudet, defining the plesiomorphic condition for mandibular morphology in Hippopotaminae, could be crucial for future phylogenetic reconstructions of the family. Mandibular morphology is a fast-evolving complex of characters, key in reconstructing the behavior and the past diversity of Hippopotamidae. Finally, this material demonstrates the potential of Napudet for augmenting the fossil record for a relatively ill-documented time interval (13–10 Ma). SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP Citation for this article: Boisserie, J.-R., C. Kiarie, F. Lihoreau, and I. Nengo. 2017. Middle Miocene Kenyapotamus (Cetartiodactyla, Hippopotamidae) from Napudet, Turkana Basin, Kenya. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1272055.
- Apr 2016
As description of enamel microstructure in mammals is mainly performed through 2D sections, interpretations of its formation and development can be misinterpreted by neglecting the complexity of its 3D arrangement. Through Simulenam, a novel software dedicated to the simulation of enamel prisms, and an updated, integrative model of decussation formation, we managed to transform 2D observations of enamel sections into full 3D representations of hippopotamoid enamel microstructure. This allowed us to reinterpret the 2D morphological characters of these taxa into geometric parameters and put a new light on how they evolved through time, with potential implications on their cellular origins – essential steps for furthering our understanding of enamel. Indeed, we also demonstrated that some of these characters could actually be non-homologous across taxa, and that there is at least two fundamentally different ways to produce enamel prism decussation in mammals.
The description of original material of anthracothere and proboscidean in the new locality of Bir el Ater 3 from East Algeria, and a thorough review of early Libycosaurus remains of Bir el Ater 2 allows us validating L. algeriensis as the smallest and earliest species of Libycosaurus and probably the earliest migrant of the genus from Asia. The presence of a Tetralophodon in the Neogene Nementcha formation might represent the earliest occurrence of the genus in Africa. These original fossil remains allow us to discuss the age of the Neogene part of the Nementcha formation close to the Serravalian/Tortonian boundary.
Intraspecific variation of endocranial structures is not widely studied in most mammals, particularly fossil mammals, which are mainly represented by a few preserved crania. However, a description of this variation is necessary to be able to study fossil mammals from an ecological and phylogenetic perspective. To facilitate further analyses on fossil equoids, digital reconstructions of the cranial endocast, petrosal bone, and bony labyrinth were created based on CT scans, taken from a wild population of 12 Equus caballus przewalskii currently being monitored. Using descriptive, biometric, and morphometric analyses, an unsuspected range of intraspecific variation for 40 endocranial characters is revealed. Intraindividual variation can be further understood through the comparison of paired organs from a single individual. These results prompt cautious consideration of these characters, as well as an index for the determination of hearing abilities or encephalization quotients. Thanks to this work, more is now known about the intraspecific variation of the external morphology of the most frequently studied structures in the endocranium of mammals and more specifically in equoids, where no such study had been undertaken until now. This will help to improve the resolution of fossil endocranial studies.
According to molecular data, hippopotamuses and cetaceans form a clade excluding other extant cetartiodactyls. Despite a wealth of spectacular specimens documenting cetacean evolution, this relationship remains poorly substantiated by the fossil record. Indeed, the evolutionary path leading from the hippo-cetacean ancestor to Hippopotamidae is plagued by missing fossil data and phylogenetic uncertainties. Only an origination within the extinct anthracotheres is compatible with molecular results, substantial filling of phyletic gaps and recent discoveries of early Miocene hippopotamids. Yet, the anthracothere stock that gave rise to Hippopotamidae has not been identified. Consequently, recent phylogenetic accounts do not properly integrate the anthracotheriid hypothesis, and relate Hippopotamidae to a stretched ghost lineage and/or close to Suina. Here we describe a new anthracothere from Lokone (Kenya) that unambiguously roots the Hippopotamidae into a well-identified group of bothriodontines, the first large mammals to invade Africa. The hippos are deeply anchored into the African Paleogene.
This contribution contains the 3D model described and figured in the following publication: Hautier L, Sarr R, Lihoreau F, Tabuce R, Marwan Hameh P. 2014. First record of the family Protocetidae in the Lutetian of Senegal (West Africa). Palaeovertebrata 38 (2)-e2
The earliest cetaceans are found in the early Eocene of Indo-Pakistan. By the late middle to late Eocene, the group colonized most oceans of the planet. This late Eocene worldwide distribution clearly indicates that their dispersal took place during the middle Eocene (Lutetian). We report here the first discovery of a protocetid fossil from middle Eocene deposits of Senegal (West Africa). The Lutetian cetacean specimen from Senegal is a partial left innominate. Its overall form and proportions, particularly the well-formed lunate surface with a deep and narrow acetabular notch, and the complete absence of pachyostosis and osteosclerosis, mark it as a probable middle Eocene protocetid cetacean. Its size corresponds to the newly described Togocetus traversei from the Lutetian deposits of Togo. However, no innominate is known for the Togolese protocetid, which precludes any direct comparison between the two West African sites. The Senegalese innominate documents a new early occurrence of this marine group in West Africa and supports an early dispersal of these aquatic mammals by the middle Eocene.
- Dec 2014
This contribution contains the 3D model described and figured in the following publication: Hautier L, Sarr R, Lihoreau F, Tabuce R, Marwan Hameh P. 2014. First record of the family Protocetidae in the Lutetian of Senegal (West Africa). Palaeovertebrata 38 (2)-e2
The Lophiodontidae are a European Eocene perissodactyl family that includes the genera Lophiaspis, Lophiodon and Paralophiodon. Despite their high specific diversity, their abundance and their dominance over Eocene large herbivores, the origin of this group still remains unclear. The La Borie locality (early Eocene, MP8-9), near Issel, Southern France, has yielded a new and well preserved skull of a new early lophiodontid. Building on this new specimen, a new phylogenetic hypothesis is proposed for Lophiodontidae, based on a cladistic analysis of dental, cranial and mandibular characters. The specimen displays a unique morphology that leads us to propose the new genus and species Eolophiodon laboriense. This monospecific genus is the sister group of the clade gathering Lophiodon and Paralophiodon. From the obtained phylogeny, it is proposed that the well-known group of derived lophiodonts might have arisen in Southern Europe soon after the origin of the family, and most probably from a Lophiaspis-like stock.
The analysis of a large sample of anthracothere remains discovered by the Mission Paléoanthropologique Franco-Tchadienne at Toros-Menalla (TM), Northern Chad, has revealed the occurrence of a single species with a large intraspecific morphological variability. Taxonomic problems triggered the necessity of naming a new species for the TM anthracotheres, Libycosaurus bahri sp. nov. The description of the craniodental remains and the analysis of their variability indicate a marked sexual dimorphism, most probably induced by sex differential growth, helping to reassess the specific diversity of Libycosaurus and its main evolutionary trends in a phylogenetic perspective. The ecological niche occupied by the new species was also further characterized in its semiaquatic, behavioural, and dietary dimensions. On these grounds we suggest that Late Miocene environmental changes, particularly habitat opening and hydrographic network fragmentation related to increased aridity, played a major role in canalizing semi-aquatic specializations and the extinction of the last African anthracotheres, as well as other bothriodontines.http://zoobank.org/urn:lsid:zoobank.org:pub:8C0AD4BD-952D-4A60-94B8-6F7A23332171
- Jul 2014
Investigations on enamel microstructure provided new data for the debate on hippopotamid origin. Observations indicated a diversity of patterns relevant to phylogenetic inferences. Within Hippopotamoidea, the distribution of these patterns seems to be in favour of a hippopotamid origin within the Palaeogene African anthracotheres. Enamel microcharacters therefore prove to be particularly relevant for future phylogenetic analysis of the superfamily, and have implications for our understanding of ecological transitions within hippopotamoids at the end of the Miocene. Indeed, unlike equids or bovids, which developed grass feeding thanks to their hypsodont molars, hippopotamoids may have had another way to exploit this resource. The combination of inter-row sheets, which appeared early in the evolutionary history of the group, and the increased thickness of radial enamel could have eased the consumption of highly abrasive graminoids. © 2014 The Linnean Society of London
Anthracotheres ("Anthracotheriidae", Hippopotamoidea, Artiodactyla, Mammalia) lived almost worldwide from the Late Eocene to the Early Pliocene, migrating early from Southeast Asia, firstly towards North America, then towards Europe and Africa (Lihoreau and Ducrocq, 2007). The members of this family were adapted to many different ecologies and successfully colonised various habitats throughout their evolutionary history. The genus Anthracotherium, along with many other mammals, arrived in Europe during the migration events linked to the Grande Coupure (MP21-22; Hooker et al., 2004) and became extinct on this continent by the end of the Oligocene (e.g., Scherler et al., 2013). Cuvier (1822) described first the remains of the "charcoal beast" Anthracotherium, creating its type species A. magnum from the Italian locality of Cadibona and the smaller A. alsaticum from the French site of Lobsann. Since then, no less than fifteen species were identified, sometimes solely based on a few remains recorded in a unique locality, varying from sizes, dental morphologies, and geographic regions (e.g., A. hippoïdeum RÜTIMEYER, 1857, A. valdense KOWALEVSKY, 1976, A. seckbachense KINKELIN, 1884). A thorough review of the European anthracotheriines made on fossils from old collections of diverse Natural History Museums allowed us to highlight important variations in the dental morphology of the different species. Based on a cladistic analysis, we suggest to split in two the representatives of European "Anthracotherium" and propose a diagnosis for a new genus. This new phylogeny challenges the old vision of the subfamily's evolutionary history in Europe.
A new Eocene locality in southern France has yielded a poorly diversified vertebrate fauna but does contain abundant material representing a new species of early equoid, Pachynolophus eulaliensis, sp. nov. Biostratigraphic data for this new locality of Sainte-Eulalie suggest a middle Ypresian age. The new species is the oldest representative of the Palaeotheriidae, here including the controversial pachynolophs. The abundant remains of this taxon from a single locality allow the recognition of a high degree of unsuspected variability within this taxon, including sexual dimorphism, thus permitting discussion of the reliability of commonly used characters. A phylogenetic analysis led us to emend the diagnosis of the genus Pachynolophus as well as to suggest the exclusion of 'Pachynolophus' hookeri from the genus. This study proposes new hypotheses of relationships among the basal Equoidea and allows us to distinguish the two main groups (Equidae and Palaeotheriidae) earlier in the Eocene, close to the reference level MP8—9. The new material appears to be a fundamental cornerstone in solving the question of the controversial systematics and phylogeny of pachynolophs. It also sheds new light on the temporal and spatial distribution of the initial radiation of European equoids.
Early hystricognathous rodents from Africa are primarily documented by two basal and extinct groups, the paraphyletic “Phiomyidae” and the Gaudeamuridae, which were particularly well diversified through the late Eocene and the early Oligocene. However, in the absence of a comprehensive late Oligocene fossil record, the evolutionary history of African hystricognathous rodents during the end of the Paleogene is unclear. Continuing field efforts in the Lokichar Basin of Kenya (western Turkana Basin) have led to the discovery of dental remains of a ‘phiomyid’ from the Lokone site LOK 13. The dental pattern of this rodent is unusual among ‘phiomyids,’ which led us to propose here a new taxon: Turkanamys hexalophus, gen. et sp. nov. Turkanamys shares a similar dental bauplan with early Afro-Asian hystricognaths (early ‘phiomyids’ and ‘baluchimyines’), and as such appears evolutionarily conservative with respect to some Oligocene and all the Miocene hystricognaths. Conversely, Turkanamys is also highly autapomorphic in developing a hexalophodont pattern on upper molars. The discovery of this peculiar rodent highlights the persistence of this ancestral ‘phiomorph’ group at the end of the Paleogene. Given the great familial diversity of hystricognaths in the early Miocene of East Africa, the virtual absence of their stem representatives in the late Oligocene record of the same province suggests either important taphonomic/sampling biases or a real absence of these families in this province at that time. This would suggest that hystricognathous rodents diversified elsewhere and colonized East Africa by the late Oligocene–early Miocene transition.
- Jun 2011
Recent excavations in northwestern Kenya have recovered a vertebrate fauna of late early or early late Oligocene age. Among the mammal remains, a fragmentary lower jaw and an isolated upper molar have been attributed to a small primate, Lokonepithecus manai gen. et sp. nov. Lokonepithecus is a primitive member of the Parapithecidae and possibly most closely related to Apidium from the Fayum. The new primate from Kenya is the youngest parapithecid known and its occurrence in the Oligocene of Kenya suggests that sub-Saharan Africa probably played a major role in the evolutionary history of several groups of mammals.
- Oct 2010
The fossil record of the Hippopotamidae can shed light on three major issues in mammalian evolution. First, as the Hippopotamidae are the extant sister group of Cetacea, gaining a better understanding of the origin of the Hippopotamidae and of their Paleogene ancestors will be instrumental in clarifying phylogenetic relationships within Cetartiodactyla. Unfortunately, the data relevant to hippopotamid origins have generally been ignored in phylogenetic analyses of cetartiodactyls. In order to obtain better resolution, future analyses should consider hypotheses of hippopotamid Paleogene relationships. Notably, an emergence of the Hippopotamidae from within anthracotheriids has received growing support, leading to reconciliation between genetic and morphological evidence for the clade Cetancodonta (Hippopotamidae + Cetacea). Secondly, full account needs to be taken of the Hippopotamidae when studying the impact of environmental change on faunal evolution. This group of semi-aquatic large herbivores has a clear and distinct ecological role and a diverse and abundant fossil record, particularly in the African Neogene. We examine three major phases of hippopotamid evolution, namely the sudden appearance of hippopotamines in the late Miocene (the "Hippopotamine Event"), the subsequent rampant endemism in African basins, and the Pleistocene expansion of Hippopotamus. Each may have been influenced by multiple factors, including: late Miocene grass expansion, African hydrographical network disruption, and a unique set of adaptations that allowed Hippopotamus to respond efficiently to early Pleistocene environmental change. Thirdly, the fossil record of the Hippopotamidae documents the independent emergence of adaptive character complexes in relation to semiaquatic habits and in response to insular isolation. The semiaquatic specializations of fossil hippopotamids are particularly useful in interpreting the functional morphology and ecology of other, extinct groups of large semiaquatic herbivores. Hippopotamids can also serve as models to elucidate the evolutionary dynamics of island mammals.
Anthracotheriidae are a group of bunodont to selenodont artiodactyls distributed throughout the Old World and North America. The earliest anthracotheriids appear in the latest middle Eocene in Asia, and they survive into the late Miocene in Africa and Asia. Because members of the family are widespread, the group has often been important for interpretations of biogeography. Anthracotheres have also been pivotal in discussions of mammalian phylogeny. In Africa, members of the family are first recorded from the late Eocene Qasr el Sagha Formation, Egypt, and the family persists through the late Miocene. During the Miocene, anthracotheres had an extended range across eastern, central, southern, and northern Africa, although their diversity in Africa appears to have always been greatest in North Africa. Black (1978) provided the first review of the entire African record of this family. The Paleogene forms have since been considerably revised by Ducrocq (1997) and the Neogene ones by Pickford (1991b). A number of studies have elucidated the systematics, paleoecology, and biogeographic relationships of African anthracotheres.
The affinities of the Hippopotamidae are at the core of the phylogeny of Cetartiodactyla (even-toed mammals: cetaceans, ruminants, camels, suoids, and hippos). Molecular phylogenies support Cetacea as sister group of the Hippopotamidae, implying a long ghost lineage between the earliest cetaceans (approximately 53 Ma) and the earliest hippopotamids (approximately 16 Ma). Morphological studies have proposed two different sister taxa for hippopotamids: suoids (notably palaeochoerids) or anthracotheriids. Evaluating these phylogenetic hypotheses requires substantiating the poorly known early history of the Hippopotamidae. Here, we undertake an original morphological phylogenetic analysis including several "suiform" families and previously unexamined early Miocene taxa to test previous conflicting hypotheses. According to our results, Morotochoerus ugandensis and Kulutherium rusingensis, until now regarded as the sole African palaeochoerid and the sole African bunodont anthracotheriid, respectively, are unambiguously included within the Hippopotamidae. They are the earliest known hippopotamids and set the family fossil record back to the early Miocene (approximately 21 Ma). The analysis reveals that hippopotamids displayed an unsuspected taxonomic and body size diversity and remained restricted to Africa during most of their history, until the latest Miocene. Our results also confirm the deep nesting of Hippopotamidae within the paraphyletic Anthracotheriidae; this finding allows us to reconstruct the sequence of dental innovations that links advanced selenodont anthracotheriids to hippopotamids, previously a source of major disagreements on hippopotamid origins. The analysis demonstrates a close relationship between Eocene choeropotamids and anthracotheriids, a relationship that potentially fills the evolutionary gap between earliest hippopotamids and cetaceans implied by molecular analyses.
- Jun 2010
The concentrations of atmospheric cosmogenic 10 Be normalized to the solubilized fraction of its stable isotope 9 Be have been measured in the authigenic phase leached from silicated continental sediments deposited since the upper Miocene in the northern Chad Basin. This method is validated by the systematic congruence with the biochronological estimations based on the fossil mammal evolutive degree of faunal assemblages. The fifty-five authigenic 10 Be/ 9 Be ages obtained along 12 logs distributed along two West–East cross sections that encompass best representative Mio-Pliocene outcrops including paleontological sites show a systematic stratigraphic decrease when considering all studied sedimentary facies extending from the Pleistocene up to 8 Ma and allow performing geologic correlations otherwise impossible in the studied area. The resulting global sequence evidences and temporally specifies the succession of the main paleoenvironments that have developed in this region since the Miocene. Under the special conditions encountered in the northern Chad Basin, this study demonstrates that the authigenic 10 Be/ 9 Be ratio may be used as a dating tool of continental sedimentary deposits from 1 to 8 Ma. The half-life of 10 Be theoretically allowing dating up to 14 Ma, it may have fundamental implications on important field research such as paleoclimatology and, through the dating of fossiliferous deposits in paleontology and paleoanthropology.
- Dec 2009
The earliest known hippopotamids, attributed to the subfamily Kenyapotaminae, are known essentially from dental remains of two species. The first was found in the middle Miocene of Kenya, the second at the beginning of the upper Miocene in eastern and northern Africa. The exact affinities of the Kenyapotaminae are critical for resolving the long debated origin of the Hippopotamidae, as part of the wider question of cetacean affinities within artiodactyls. We performed the first detailed comparative description, character by character, of kenyapotamines, using the following putatively related taxa: Hippopotaminae, Suoidea, and Anthracotheriidae. The development of an improved nomenclature for the dentition facilitates comparisons amongst a wide array of cetartiodactyls. This has permitted the first assessment of the phylogenetic position of Kenyapotaminae using a cladistic analysis. This work provides an emendation of kenyapotamine taxonomy and diversity. Kenyapotaminae are indeed closely related to Hippopotaminae and should be kept within Hippopotamidae, the late Miocene kenyapotamines not necessarily being the forerunners of the first known hippopotamines. Hippopotamidae are deeply nested within anthracotheriids, with crown bothiodontines as sister group, and any close affinities with Suoidea should be rejected. This reinforces a scenario linking cetaceans to Hippopotamoidea (Hippopotamidae + Anthracotheriidae), possibly via other early Palaeogene artiodactyls.
A new fossiliferous locality is reported from southwestern France (Moissac III) that yielded two skulls referred to the anthracotheriid Elomeryx crispus and the rhinocerotid Protaceratherium albigense, and an isolated rodent tooth. The anthracotheriid skull indicates a close relationship with E. borbonicus based on its cranial morphology. The rhinocerotid skull improves our knowledge concerning its anterior dentition, cranial morphology and proportions, and enables a more precise specific diagnosis. We suggest an early late Oligocene biochronological age (Mammal Paleogene European reference level MP25-26) for Moissac III, which is substantiated by the co-occurrence of P. albigense and of the theridomyid rodent Issiodoromys cf. pauffiensis. The European stratigraphic range of E. crispus, so far restricted to the late Eocene-early Oligocene interval (MP18-MP22), extends up to the MP25-26, which in turn supports an origination of ‘Miocene bothriodontines’ from a European ancestor.
- Mar 2009
New fossil remains of the proboscidean genus Anancus are described. Among them, a complete skull allows us to revisit for the first time the entire Chadian Anancus fossil record. This genus occurred in the Old World from the late Miocene up to the early Pleistocene. The analysis of dental and cranial characters was allowed individual variations from specific characters to be distinguished. In this study we show that Anancus kenyensis and Anancus osiris are very likely synonym taxa which leads us to emend the diagnosis of A. kenyensis. In addition, this study shows that dental characters in anancines lineage are of little significance for biostratigraphical inference, by contrast to previous works. This study brings new data about the phylogenetical and palaeobiogeographical history of the African anancines.
Captive animals are used extensively in actualistic bite mark studies, but such animals can exhibit novel physical, functional, and behavioral traits that may affect their utility as proxies for wild relatives, much less extinct analogues. Within Crocodylia, qualitative trends toward broader snouts and splayed teeth in captive animals have been reported, and preliminary morphometric analyses have identified other traits reflecting possible paedomorphic tendencies in the ontogeny of the captive cranium. To address how these morphological differences might affect resulting bite marks, eighty-three specimens of Alligator mississippiensis representing sixty-three wild and twenty captive animals were observed. Snout shape and individual tooth placement were characterized using 2D, landmark-based techniques and interpreted using a variety of ordination and statistical methods. Results indicate a weak but significant difference between captive and wild individuals, but only if their origin is already known. This implies that at a gross scale, the differences between captive and wild bite marks should not differ with regards to snout shape and tooth spacing. Several attempts to calculate tooth splay were attempted and demonstrated that while tooth angle is being affected by this process, socket location is apparently not. These results indicate that while snout shape and tooth spacing do not introduce significant bias into bite mark studies based on captive specimens, the effects of tooth splay still need further consideration. Until tooth splay can be accounted for, collections of bite marks created by captive crocodylians should be supplemented with and compared to similar bone modifications made by wild animals. This approach provides a case study for future work quantifying differences between captive and wild morphotypes of other taxa used in actualistic taphonomic studies of bite marks.
- Jun 2008
The genus Primelephas Maglio 1970 gathers two primitive species of Elephantinae, only known through dental remains. A large sample of new fossils, discovered by the MPFT field missions in northern Chad Mio-Pliocene localities and attributed to this genus, allowed questioning the validity of one of the species. An intrageneric morphological variability analysis led us to consider this species as a synonym. Therefore, Primelephas should be conserved as a monospecific genus, P. korotorensis being its type and sole species. The provincialism previously described for Primelephas is rejected in favour of a large African distribution of P. korotorensis.
Ages were determined at two hominid localities from the Chad Basin in the Djurab Desert (Northern Chad). In the Koro Toro fossiliferous area, KT 12 locality (16°00′N, 18°53′E) was the site of discovery of Australopithecus bahrelghazali (Abel) and in the Toros-Menalla fossiliferous area, TM 266 locality (16°15′N, 17°29′E) was the site of discovery of Sahelanthropus tchadensis (Toumaï). At both localities, the evolutive degree of the associated fossil mammal assemblages allowed a biochronological estimation of the hominid remains: early Pliocene (3–3.5 Ma) at KT 12 and late Miocene (≈7 Ma) at TM 266. Atmospheric ¹⁰Be, a cosmogenic nuclide, was used to quasicontinuously date these sedimentary units. The authigenic ¹⁰Be/⁹Be dating of a pelite relic within the sedimentary level containing Abel yields an age of 3.58 ± 0.27 Ma that points to the contemporaneity of Australopithecus bahrelghazali (Abel) with Australopithecus afarensis (Lucy). The 28 ¹⁰Be/⁹Be ages obtained within the anthracotheriid unit containing Toumaï bracket, by absolute dating, the age of Sahelanthropus tchadensis to lie between 6.8 and 7.2 Ma. This chronological constraint is an important cornerstone both for establishing the earliest stages of hominid evolution and for new calibrations of the molecular clock. • beryllium-10 • absolute dating • hominid site • Abel • Toumaï
- Jan 2008
The high proportion of crystallized apatite forming the bones and teeth should theoretically allow the use of fission track analysis to date vertebrate fossils when burying of the fossiliferous series did not subject them to temperatures exceeding 60 °C. However several major obstacles arise such as the complexity of fossils' internal structures, diagenetic modifications and substitutions of the hydroxyapatite by other minerals, and massive U uptake or loss during diagenesis. In this work, those various problems are addressed combining optical microscope observation of the fossils, a systematic fission track analysis of the best samples, α and γ spectrometry and Secondary Ion Mass Spectrometry. Even if the problems caused by internal structures and mineral substitutions can be solved, U movements in and out of the fossils are generally too complex to allow fission track analysis dating of the fossils.
- Mar 2007
New fossil remains of the anthracothere genus Merycopotamus Falconer and Cautley, are described. Most of them were discovered by the Harvard University and Geological Survey of Pakistan joint research project (Y-GSP) in the well-dated Middle and Late Miocene deposits of the Potwar Plateau in northern Pakistan. This new material led us to revise the systematics of the genus with the validation of three species, M. nanus Falconer (M. pusillus Lydekker), M. dissimilis Falconer and Cautley, and M. medioximus Lihoreau et al., and allowed us to determine precisely their chronological distributions in a continuous Neogene sequence. Other specimens reported from the late Miocene deposits of the Khorat Plateau in north-east Thailand by the Department of Mineral Resources are the first remains of Merycopotamus to have been discovered in that region and are attributed to M. medioximus. These discoveries indicate a wider geographical distribution of the genus in the early Late Miocene. Anatomical investigations highlight the evolution of Merycopotamus through the Miocene towards more amphibious habits. Palaeobiogeographical and palaeoecological information for Merycopotamus stress the role of the Himalayan orogenesis as a dispersal barrier and the impact of a major global regression event on the evolution of Indian Subcontinent faunas from the Middle Miocene to the Late Pliocene.
- Oct 2006
Anthracotheriid remains from several Paleogene localities of central and eastern Asia have been re-examined. Several fossil remains attributed to the genera Bothriodon, Brachyodus and Hyoboops can be referred to Elomeryx which extends the geographical distribution of the genus to the whole area of Asia. These results demonstrate the role that Asia played in the biogeographical history of mammals and further support the proposed origin of North American Elomeryx from an Asian ancestor. (c) 2006 Elsevier Ltd. All rights reserved.
- Jul 2006
Molecular data analyses blew the problem of hippo origins up to the level of a broader question: cetacean and artiodactyl relationships. Recently, new morphology-based studies strongly supported a hippo origin within Miocene bothriodontines, which are selenodont anthracotheres. Based on these results, two new scenarios for hippo emergence are proposed here. Palaeoenvironmental and evolutionary issues related to these scenarios are discussed. To cite this article: J.-R. Boisserie, C. R. Palevol 5 (2006).
Recent discovery of an abundant and diverse late Miocene fauna at Toros-Ménalla (Chad, central Africa) by the Mission Paléoanthropologique Franco-Tchadienne provides a unique opportunity to examine African faunal and hominid evolution relative to the early phases of the Saharan arid belt. This study presents evidence from an African Miocene anthracotheriid Libycosaurus, particularly well documented at Toros-Ménalla. Its remains reveal a large semiaquatic mammal that evolved an autapomorphic upper fifth premolar (extremely rare in Cenozoic mammals). The extra tooth appeared ≈12 million years ago, probably in a small northern African population isolated by climate-driven fragmentation and alteration of the environments inhabited by these anthracotheriids [Flower, B. P. & Kennett, J. P. (1994) Palaeogeogr. Palaeoclimatol. Palaeoecol. 108, 537–555 and Zachos, J., Pagani, M., Sloan, L., Thomas, E. & Billups, K. (2001) Science 292, 686–693]. The semiaquatic niche of Libycosaurus, combined with the distribution and relationships of its late Miocene species, indicates that by the end of the Miocene, wet environments connected the Lake Chad Basin to the Libyan Sirt Basin, across what is now the Sahara desert. • Anthracotheriidae • Chad • Libya • paleobiogeography • early hominids
The origin of late Neogene Hippopotamidae (Artiodactyla) involves one of the most serious conflicts between comparative anatomy and molecular biology: is Artiodactyla paraphyletic? Molecular comparisons indicate that Cetacea should be the modern sister group of hippos. This finding implies the existence of a fossil lineage linking cetaceans (first known in the early Eocene) to hippos (first known in the middle Miocene). The relationships of hippos within Artiodactyla are challenging, and the immediate affinities of Hippopotamidae have been studied by biologists for almost two centuries without resolution. Here, we compare opposing hypotheses implicating several “suiform” families. This morphological analysis of a comprehensive set of taxa and characters offers a robust solution to the origins of Hippopotamidae. This family appears to be deeply nested within the otherwise extinct artiodactyl family Anthracotheriidae, most precisely within the most advanced selenodont forms. The proposed sister group of hippos is the middle to late Miocene African semiaquatic Libycosaurus. Any close relationships of hippos with suoids, particularly with Tayassuidae, are rejected. Furthermore, the clade (Hippopotamidae, Anthracotheriidae) is proposed as the sister group of the Cetacea, offering broad morphological support for a molecular phylogeny, such support being also consistent with the fossil record. Corroboration of this relationship requires an exploration of anthracothere affinities with other Paleogene artiodactyls. Among those, the position of Ruminantia is a central question, still to be solved. Further progress in this debate is likely to come from morphological studies of paleontological data, whether known or still to be discovered. • hippo origin • phylogeny • Anthracotheriidae • suoids • archaeocetes
- Jan 2005
The old debate on hippopotamid origins is still unresolved, balancing between two main phylogenetic hypotheses: origins within the Anthracotheriidae vs. origins within the Tayassuidae. The characters used in the literature to support one, the other, or both hypotheses were re-examined in light of a better known primitive hippopotamid morphology. A cladistic analysis was performed on the basis of these characters. On the one hand, although many features similar in hippopotamuses and anthracotheres appear to have evolved in parallel, the family Anthracotheriidae remains the best putative hippopotamus stem group on the basis of the reviewed characters. However, the precise identification of a stem group within this family is still uncertain. On the other hand, the lineage proposed in the tayassuid hypothesis should not be retained, being mostly based on some incorrect observations and without taking into account the derived or primitive nature of the features. The anatomic similarities seen between modern peccaries and Hippopotamus amphibius are the results of convergences between advanced species of both families.
- Dec 2004
New anthracotheriid remains, discovered by the H-GSP in well-dated localities from the Potwar plateau in the North of Pakistan, between 10.4 and 8.6 Ma, are described and attributed to Merycopotamus medioximus nov. sp. This new species displays an intermediate morphology between the older M. pusillus and the more recent M. dissimilis. These results permit to emend the Merycopotamus diagnosis. To cite this article: F. Lihoreau et al., C. R. Palevol 3 (2004).
- Jul 2004
‘Toumaï’, Late Miocene of Chad, the new earliest member of the human branch. The new Chadian hominid Sahelanthropus tchadensis Brunet et al., 2002, nicknamed ‘Toumaï’, recovered by the MPFT (Mission paléoanthropologique franco-tchadienne, scientific collaboration between the University of Poitiers, University of N’Djamena and CNAR, National Center for the support of Science of N’Djamena) from the Late Miocene of Toros-Menalla (Djurab desert) is associated with a vertebrate fauna (more than 45 species) for which the mammalian component (at least 25 species) indicates a biochronological age close to 7 Ma. The fauna comprises vertebrates that are aquatic (fish, turtles, crocodiles) and amphibious (anthracotheriids, hippopotamids) but also species adapted to the gallery and islet forests (monkeys), wooded savanna (proboscideans, giraffids, suids, etc) and grassland (bovids, tridactyl equids). Sedimentological data (aeolian sandstones, perilacustrine sandstones, diatomites) agree with this mosaic of environments and indicate a vegetated perilacustrine belt between lake and desert. The new hominid is probably temporally close to the common ancestor of chimpanzees and humans but displays a unique combination of primitive and derived characters that clearly shows a close relationship with later hominids rather than with chimpanzees or gorilla. The geographic location of Toumaï, 2500 km west of the Rift Valley, along with its great antiquity, suggest an early widespread hominid distribution (Sahel and East Africa, at least by 6 Ma), and a somewhat earlier chimpanzee-human divergence (at least by 7 Ma ago) than previously indicated by many molecular studies. To cite this article: M. Brunet et al., C. R. Palevol 3 (2004).
- Feb 2004
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. New unpublished remains of small Anthracotheriinae are described. First, materials from the upper Oligocene (MP 30) locality of La Milloque, southwest France, permit a review of the species Microbunodon minimum. Thereafter, fossils from the middle and late Miocene of the Potwar Plateau, Pakistan are attributed to the European genus Microbunodon. Microbunodon milaensis sp. n. from the Nagri Formation (between 10.3 and 9.2 Ma), Pakistan, is described and the species M. silistrensis from the Lower Manchar Formation (between 16 and 15 Ma) and from the Chinji Formation (between 12.7 and 11.5 Ma), Pakistan, is reviewed. The new species represents the last occurrence of the subfamily Anthracotheriinae, around 9.3 Ma. Similar materials from the Bugti and Siwalik Hills were previously considered as a small Anthracotherium. Comparisons with M. minimum from the European late Oligocene lead to a complete revision of the genus and permit definition of a new set of characters, which separate Microbunodon from Anthracotherium. A cladistic analysis reconsiders phylogenetic relationships among Anthracotheriinae, separating an Anthracothema–Anthracotherium clade and an Anthracokeryx–Microbunodon clade. Microbunodon appears to stem from the Asian late Eocene–lower Oligocene genus Anthracokeryx. These results imply a new distribution of the genus Microbunodon showing exchanges between Europe and Asia during the late Oligocene and probably the lower Miocene.
The search for the earliest fossil evidence of the human lineage has been concentrated in East Africa. Here we report the discovery of six hominid specimens from Chad, central Africa, 2,500 km from the East African Rift Valley. The fossils include a nearly complete cranium and fragmentary lower jaws. The associated fauna suggest the fossils are between 6 and 7 million years old. The fossils display a unique mosaic of primitive and derived characters, and constitute a new genus and species of hominid. The distance from the Rift Valley, and the great antiquity of the fossils, suggest that the earliest members of the hominid clade were more widely distributed than has been thought, and that the divergence between the human and chimpanzee lineages was earlier than indicated by most molecular studies.
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.