|Mandible of A. bahrelghazali (KT12 / H1)|
Brunet et al., 1995
Australopithecus bahrelghazali is a hominin species that inhabited the Bahr el Ghazal region in Central Africa around 3.6 million years ago. It was discovered in 1995 by a Franco-Chadian team led by the paleontologist Michel Brunet. All four fossils that have been found since 1995 are jaw (mandibular or maxillar) fragments.
A. bahrelghazali is the only australopithecine species found in Central Africa. It is also of great importance as it is the first fossil to show that there is a geographical "third window", that is, beyond East Africa and South Africa, of early hominin evolution. The locality is roughly 2,500 km (1,600 mi) west of the East African Great Rift Valley, making it far removed from what is broadly thought to be the "cradle" area of human evolution.
To date, four fossils have been described. Based on the sediments where the fossils were found, A. bahrelghazali was dated by beryllium-based radiometric dating as living about 3.6 million years ago.
A mandibular fragment found at Chad east of the Bahr el Ghazal ("river of gazelles") to about 45 km (28 mi) from the fort of Koro Toro, by the Franco-Chadian team of Michel Brunet January 23, 1995 on the site called KT12. Named after the fossil valley near where it was discovered, cataloged KT12/H1, the holotype consists of a mandibular fragment, a lower second incisor, both lower canines, and all four of its premolars, still affixed within the dental alveoli. The KT-12/H1 specimen was nicknamed Abel by Brunet as a dedication to his deceased colleague Abel Brillanceau.
A third fossil, a fragment of left maxilla, was collected on January 16, 1996, at the KT13 site, not far from KT12. Cataloged KT13-96-H1, it appears in a scientific article in 1997 as Australopithecus sp. indet. before being named Australopithecus bahrelghazali in 2012.
A fourth fossil mandibular fragment with two teeth was unearthed on July 18, 2000, a few kilometers south of the site KT13 on the new site of KT40. The three sites of hominids KT12, KT13 and KT40 are located at the foot of the same sandy cord, the Goz Kerki, testimony of the former shoreline of Lake MégaTchad. The fossil potential of this sector therefore remains important.
The KT-12/H1 mandible has similar features to the dentition of Australopithecus afarensis, which has caused researcher William Kimbel to argue that Abel is not a separate species, but "falls within the range of variation" of the species Australopithecus afarensis. By 1996, Brunet and his team classified KT-12/H1 as the holotype specimen for Australopithecus bahrelghazali. This claim is difficult to substantiate, as the describers, contrary to the International Code of Zoological Nomenclature, have kept the specimen locked away from inspection by the general paleoanthropological community.
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