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Australopithecus bahrelghazali

Australopithecus bahrelghazali
Mandible of "A. bahrelghazali" (KT12 / H1)
Mandible of A. bahrelghazali (KT12 / H1)
Scientific classification edit
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Suborder: Haplorhini
Infraorder: Simiiformes
Family: Hominidae
Subfamily: Homininae
Tribe: Hominini
Genus: Australopithecus
Species:
A. bahrelghazali
Binomial name
Australopithecus bahrelghazali
Brunet et al., 1995
Synonyms

Praeanthropus bahrelghazali

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.[1][2] 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.

Fossils

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.[3]

KT-12/H1 (Abel)

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.[4][5]

KT12/H2

An upper premolar of another individual was found in the same place in January 1996. This paratype is cataloged KT12/H2.[4][6][7]

KT13-96-H1

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.[8][9][10]

KT40 fossil

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.[11]

Controversy

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.[8] 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.[12]

See also

References

  1. ^ Ann Gibbons (2007). The First Human. Doubleday Publishing Group. p. 8. ISBN 978-0307279828. Retrieved 2015-03-18.
  2. ^ John Reader (2011). Missing links : in search of human origins. p. 393. Oxford University Press, New York, ISBN 978-0-19-927685-1.
  3. ^ Lebatard, Anne-Elisabeth; Bourlès, Didier L.; Duringer, Philippe; Jolivet, Marc; Braucher, Régis; Carcaillet, Julien; Schuster, Mathieu; Arnaud, Nicolas; Monié, Patrick; Lihoreau, Fabrice; Likius, Andossa; Taisso Mackaye, Hassan; Vignaud, Patrick; Brunet, Michel (2008). "Cosmogenic nuclide dating of Sahelanthropus tchadensis and Australopithecus bahrelghazali: Mio-Pliocene hominids from Chad". Proc. Natl. Acad. Sci. U.S.A. 105 (9): 3226–3231. Bibcode:2008PNAS..105.3226L. doi:10.1073/pnas.0708015105. PMC 2265126. PMID 18305174.
  4. ^ a b Brunet, Michel; Beauvilain, Alain; Coppens, Yves; Heintz, É.; Moutaye, A.H.E; Pilbeam, D. (1995). "The first australopithecine 2,500 kilometres west of the Rift Valley (Chad)". Nature. 378 (6554): 273–275. Bibcode:1995Natur.378..273B. doi:10.1038/378273a0. PMID 7477344.
  5. ^ Brunel, Michel; Beauvilain, A.; Coppens, Yves; Heintz, É.; Moutaye, A. H. E; Pilbeam, D. (1996). "Australopithecus bahrelghazali, une nouvelle espèce d'Hominidé ancien de la région de Koro Toro (Tchad)". Comptes Rendus des Séances de l'Académie des Sciences. 322: 907–913.
  6. ^ Brunet, M.; Beauvilain, A.; Coppens, Yves; Heintz, É.; Moutaye; Pilbeam, D. (1996). "Australopithecus bahrelghazali, une nouvelle espèce d'Hominidé ancien de la région de Koro Toro (Tchad)". Comptes Rendus des Séances de l'Académie des Sciences. 322: 907–913.
  7. ^ Australopithecus bahrelghazali, 'Abel'.
  8. ^ a b Tchad, un nouveau site à Hominidés Pliocène. Comptes Rendus des Séances de l'Académie des Sciences, t. 324, série IIa, p. 341 à 345.
  9. ^ Lee-Thorp J., Likius A., Mackaye H.T., Vignaud P., Sponheimer M. et Brunet M. Isotopic evidence for an early shift to C4 resources by Pliocene hominins in Chad et dans 'Supporting information' de cet article.
  10. ^ The jawbone of the Australopithecus bahrelghazali of KT13.
  11. ^ Mandibular symphysis of the Hominid of KT40.
  12. ^ Schwartz, Jeffrey H., and Ian Tattersal. 2005 The Human Fossil Record, vol.4: Craniodental Morphology of Early Hominids (Genera Australopithecus, Paranthropus, Orrorin) and Overview. John Wiley and Sons, New Jersey.

Bibliography

  • Beauvilain, Alain (2003). Toumaï, l'aventure humaine. Paris: La Table Ronde. p. 239.
  • Gibbons, Ann (2006). The first human, the race to discover our earliest ancestors. New York: Doubleday. p. 306.
  • Leakey, Mary; Walker, A (1997). Antiguos fósiles de homínidos en África. Investigación y Ciencia. p. 75.
  • Reader, John (2011). Missing links. In search of human origins. New York: Oxford University Press. p. 538.

External links