Start Cosmogenic nuclide dating of sahelanthropus tchadensis

Cosmogenic nuclide dating of sahelanthropus tchadensis

- géologie des remplissages karstiques associée à la recherche des gisements à vertébrés, hominidés compris.

Because no postcranial remains (bones below the skull) have been discovered, it is as of yet unknown whether Sahelanthropus tchadensis was indeed bipedal or two-footed, although claims for an anteriorly placed foramen magnum suggests that this may have been the case, some paleontologists have disputed this interpretation of the basicranium. The fossils were discovered in the Djurab Desert of Chad by a team of four led by Michel Brunet; three Chadians, Adoum Mahamat, Djimdoumalbaye Ahounta and Gongdibé Fanoné, and Frenchman, Alain Beauvilain et al. Sahelanthropus may represent a common ancestor of humans and chimpanzees; no consensus has been reached yet by the scientific community.

All known material of Sahelanthropus were found between July 2001 to March 2002 at three sites (TM 247, TM 266 which yielded most of the material, and TM 292). tchadensis is the oldest known human ancestor after the split of the human line from that of chimpanzees. The original placement of this species as a human ancestor but not a chimpanzee ancestor would complicate the picture of human phylogeny.

Le crâne, cinq fragments de mâchoire, quelques dents et surtout une diaphyse de fémur gauche (TM266-01-063) ayant pu appartenir à neuf individus ont été découverts de juillet 2001 à mars 2002 sur le site 266 de Toros-Menalla et sur deux autres sites proches.

La revue Nature publie trois articles sur cette découverte, dont deux de l'équipe, dans son numéro de juillet 2012.

The bones were found far from most previous hominin fossil finds, which are from Eastern and Southern Africa. In particular, if Toumaï is a direct human ancestor, then its facial features bring the status of Australopithecus into doubt because its thickened brow ridges were reported to be similar to those of some later fossil hominids (notably Homo erectus), whereas this morphology differs from that observed in all australopithecines, most fossil hominids and extant humans.

However, an Australopithecus bahrelghazali mandible was found in Chad by Beauvilain A., Brunet M. Another possibility is that Toumaï is related to both humans and chimpanzees, but is the ancestor of neither.

Mes thèmes de recherche portent sur 2 axes principaux : - faciès de dépôts, paléoenvironnements et traces fossiles des zones continentales à margino-littorales. J., BIDEAU H., DURINGER Ph., SCHROEDER A., THALMANN F., MARQUES C.

Une attention particulière est portée sur les comparaisons entre les milieux actuels et anciens.

Lo interesante de estos hallazgos, además de su cercanía a la fecha de la divergencia, es que existen en la mayoría de los casos indicios de algún tipo de bipedalismo, característica propia del linaje de los homininos (que incluye todas las especies de Australopithecus y Homo), de la que carecen los actuales grandes simios. “Orrorin tugenensis femoral morphology and the evolution of hominin bipedalism”.

- Estos fósiles fueron hallados en el Desierto del Djurab (Chad) en el yacimiento de Toros-Menalla y se datan entre 6 y 7 Ma.

Physical Review Letters 97 (2) 028001 (1-4) DURINGER Ph., SCHUSTER M., GENISE J. Palaeogeography, Palaeoclimatology, Palaeoecology 251, 323-353.