Louis de Bonis

A new hominid from the Upper Miocene of Chad, Central Africa

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.

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.

New remains of Mesopithecus (Primates, Cercopithecoidea) from the late Miocene of Macedonia (Greece), with the description of a new species

ABSTRACT Numerous remains of Mesopithecus have recently been recovered from the late Miocene mammalian localities of Macedonia, northern Greece. Three mandibles from the early Turolian are identified as M. delsoni, sp. nov., probably ancestral to M. pentelicus of Pikermi. Others, dated to the latest Turolian, differ from M. pentelicus, but most of the teeth are so worn that they must be identified as Mesopithecus, aff. M. pentelicus. A last set, coming also from the latest Turolian, could possibly be attributed to Mesopithecus, cf. M. monspessulanus. The evolution of the genus Mesopithecus can be used as a biostratigraphic tool in late Miocene continental deposits.

The Phylogenetic and Functional Implications of Ouranopithecus macedoniensis

The anatomy of fossil mammals is the key to understanding their place among beings, living or fossil. Anatomical characters allow one to both recognize phyletic positions and provide hypotheses on the modes, processes, and even causality of evolution. Most anatomical changes must correspond more or less to a change in adaptation. The new features are on the one hand derived, in a phyletic sense, and on the other hand they are adaptations to a new way of life. These new features help to characterize and to distinguish the younger taxa that emerge from a lineage. For a different way of life, organs must have different functions and, generally, a different shape or a different size.

Three-dimensional analysis of mandibular dental root morphology in hominoids

Although often preserved in the fossil record, mandibular dental roots are rarely used for evolutionary studies. This study qualitatively and quantitatively characterizes the three-dimensional morphology of hominoid dental roots. The sample comprises extant apes as well as two fossil species, Khoratpithecus piriyai and Ouranopithecus macedoniensis. The morphological differences between extant genera are observed, quantified and tested for their potential in systematics. Dental roots are imaged using X-ray computerized tomography, conventional microtomography and synchrotron microtomography. Resulting data attest to the high association between taxonomy and tooth root morphology, both qualitatively and quantitatively. A cladistic analysis based on the dental root characters resulted in a tree topology congruent with the consensus phylogeny of hominoids, suggesting that tooth roots might provide useful information in reconstructing hominoid phylogeny. Finally, the evolution of the dental root morphology in apes is discussed.

Lophocyon paraskevaidisi,a new viverrid (Carnivora, Mammalia) from the Middle Miocene of Chios Island, Greece

Abstract Among the material collected in 1991 and 1993 from the Middle Miocene locality of Thymiana, Chios island, a large number of specimens belong to a viverrid carnivore. This is the first discovery of a carnivore species in this locality. All specimens were unearthed from one level (level “Thymiana B” or THB) and represent a new species of the genus Lophocyon . The morphology of the upper and lower teeth of this species is very different from those of Sivanasua and Euboictis . The smaller size, the more molarized teeth and the less developed cingulum distinguish the Chios lophocyonine from the sole known species Lophocyon carpathicus (from the middle Miocene locality of Kosice-Baukov) and allow us to recognize a new species, named Lophocyon paraskevaidisi sp. nov.

Mesopithecus (Primates, Cercopithecidae) from the turolian locality of Vathylakkos 2 (Macedonia, Greece)

Two skulls, two mandibles and some postcranials ofMesopithecus from the locality “Vathylakkos 2” of Axios Valley (Macedonia, Greece) enlarge our knowledge about the genus and its differentiation. The new material together with an old skull from the same locality is compared with the Pikermi, “Ravin des Zouaves 5” (Axios Valley), and Maramena (Serres basin) samples. It is concluded that the VathylakkosMesopithecus resemblesM. pentelicus from Pikermi, as wellM. delsoni from “Ravin des Zouaves 5” and it is referred asMesopithecus sp. aff.M. pentelicus. The biochronological age of “Vathylakkos 2” has been considered as MN 12, while recent magnetostratigraphic data indicate an age of about 7.5 Ma. This age confirms the position of the VathylakkosMesopithecus between Pikermi and “Ravin des Zouaves 5”. Some dental indices compared with those of the RecentCercopithecus suggest that the Vathylakkos sample is monospecific.KurzfassungZwei Schädel, zwei Mandibeln und verschiedenes postkraniales Material vonMesopithecus aus der Fundstelle „Vathylakkos 2“ aus dem Axios-Tal (Mazedonien, Griechenland) erweitern die Kenntnis der Gattung und ihrer Evolution. Zusammen mit einem schon bekannten Schädel von dieser Fundstelle wird das neue Material mit den Funden aus Pikermi, „Ravin des Zouaves 5“ (Axios-Tal) und Maramena (Becken von Serres) verglichen. Das Material vonMesopithecus aus Vathylakkos ähneltM. pentelicus aus Pikermi, aber auchM. delsoni aus „Ravin des Zouaves 5“ und wird zuMesopithecus sp. aff.M. pentelicus gestellt. Das biostratigraphische Alter von „Vathylakkos 2“ wird als MN 12 angesehen, und neue magnetostratigraphische Daten ergeben ein Alter von etwa 7,5 Ma. Dieses Alter bestätigt die Stellung desMesopithecus von Vathylakkos zwischen dem von Pikermi und dem von „Ravin des Zouaves 5“. Der Vergleich einiger Dentalindizes vonMesopithecus undCercopithecus machen es wahrscheinlich, dass die Funde aus Vathylakkos nur eine Art repräsentieren.

Enamel Hypoplasia in a Pliocene Hominid from Chad

Abel is the first Australopithecine known west of the East African Rift Valley. The fossil finds include a perisymphyseal fragment of an adult mandible with well-preserved crowns of the right I 2 -P 4 and the left C-P 4 . Abels dentition displays many enamel defects, which are described in detail for each tooth. Pitting affected every tooth, while larger, shallow depressions were observed on the canines alone. From two to four pit bands occurred on the different teeth, each resulting from a separate hypoplastic episode. In modern humans, a large number of causes, both environmental and genetic, have been suggested for such enamel defects. It seems probable that Abels pathology was systemic. However, the occurrence of a number of bands and the variable intensity of the attacks make it difficult to say whether there was a single, repetitive cause or different etiologies. Possible causes discussed here include recurrent fevers and seasonal nutritional deficiencies.

The genus Stenoplesictis Filhol (Mammalia, Carnivora) from the Oligocene deposits of the Phosphorites of Quercy, France

ABSTRACT The discovery of new remains assigned to Stenoplesictis (Feliformia, Carnivora) in the deposit of Quercy (France) allows a more precise study of this genus. S. cayluxi Filhol, 1880 and S. minor Filhol, 1882, two species previously described by Filhol, are synonymized. A new species, Stenoplesictis crocheti, is described. It is represented by dental remains and two well preserved skulls. The basicranial anatomy is studied with special focus on the auditory region. Stenoplesictis may be a primitive feloid, like the extant Nandinia binotata. Some other material recently assigned to the genus is discussed. The African and Asian material differs from the European specimens, especially the morphology of the teeth and is excluded from the genus. Therefore, an Asian origin of the genus can not be demonstrated and the presence of Stenoplesictis in Asia remains to be confirmed.