Australopithecus bahrelghazali

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Australopithecus bahrelghazali
The lower jaw KT 12 / H1

The lower jaw KT 12 / H1

Temporal occurrence
Pliocene
3.5 to 3 million years
Locations
Systematics
Human (Hominoidea)
Apes (Hominidae)
Homininae
Hominini
Australopithecus
Australopithecus bahrelghazali
Scientific name
Australopithecus bahrelghazali
Brunet et al., 1996
The site in Chad

Australopithecus bahrelghazali is a species of the extinct genus Australopithecus . Fossils thatwere assigned to Australopithecus bahrelghazali come from a layer ofmaximum 3.5 million years old atthe site KT 12 in northern Chad .

The classification of the finds as an independent species is controversial. Their significance lies primarily in the evidence of a much larger distribution area of ​​the australopithecines than previously assumed: from the Afar triangle in Ethiopia across the East African Rift to around 2500 kilometers to the west.

Naming

Australopithecus is an artificial word . The name of the genus is derived from Latin australis ("southern") and Greek πίθηκος, old Gr. pronounced píthēkos ("monkey"). The epithet bahrelghazali refers to the site in the river bed of the Bahr al Ghazal ( Arabic : river of the gazelles ). Australopithecus bahrelghazali means "southern monkey from the gazelle river".

Initial description

The holotype of Australopithecus bahrelghazali is the first fossil of the species to be discovered, a partially preserved lower jaw (archive number KT 12 / H1), which was found in 1995 at Koro Toro ( location KT 12 ; geodata: 15 ° 58'10 N, 18 ° 52'46 E ) had been recovered. Furthermore, only one isolated tooth was discovered.

Excavation director Michel Brunet from the Mission Paléoanthropologique Franco-Tchadienne nicknamed the lower jaw "Abel" in memory of his colleague and geologist Abel Brillanceau from the University of Poitiers who died of malaria during excavations in Cameroon .

features

The discoverers of the two fossils argued that the teeth of Australopithecus bahrelghazali have a thicker enamel layer than Ardipithecus ramidus , which sets it apart , while the bone structure of the lower jaw and the tooth roots of the preserved premolars differ from the conditions in Australopithecus afarensis . However, there are no indications of body size, brain volume or certain behaviors due to the very modest evidence; numerous researchers interpret the finds from Chad as a local variant of Australopithecus afarensis .

From the same layer from which the fossils of Australopithecus bahrelghazali come, fossils of various other animal and plant species were recovered. The researchers determined among other fossil bones of terrestrial species from the group of pigs , elephants and Stegodonten , giraffes , antelopes ( Parmularius ), springbok , sivatherium ( Sivatherium ), white rhinos , horses ( Hipparion ), cattle and waterbuck . They also found remains of aquatic species from the groups of perch and catfish , softshell turtles , crocodiles ( Tomistoma ), ducks , hippos ( Hexaprotodon ) and otters . From the relatively large proportion of cattle and springboks in the fossils, it was concluded that the habitat of Australopithecus bahrelghazali - similar to the other Australopithecus species - consisted of water areas, wooded areas and tree-covered grasslands ( savannas ); this interpretation was supported by the absence of forest goats and primates other than Australopithecus . At the same time, however, the evidence of giraffes showed that there must have been at least a certain number of trees.

On the basis of the ratio of 12 carbon atoms to 13 carbon atoms in tooth enamel , it was deduced that Australopithecus bahrelghazali lived in particular on C 4 plants , that is, mainly on grasses . However, Australopithecus bahrelghazali - in contrast to the much younger species Paranthropus boisei - does not have any special adaptation of its teeth to relatively hard grass. It was therefore argued that the food intake of Australopithecus bahrelghazali is probably most comparable to that of the jeladas living today , which feed partly on grass and grass seeds, partly on roots and tubers.

Dating

According to the first description, the fossils were initially dated biostratigraphically (using key fossils ) to an age of around 3.5 to 3.0 million years. Another dating in 2008 showed an age of 3.58 ± 0.27 million years. The objection to the dating of the finds in 2008 was that they had not been discovered in situ , and that a shift due to geological or other processes could therefore not be ruled out.

See also

literature

Web links

Commons : Australopithecus bahrelghazali  - Collection of images, videos and audio files

Individual evidence

  1. ↑ Michel Brunet , Alain Beauvilain, Yves Coppens , Emile Heintz, Aladji HE Moutaye and David Pilbeam : Australopithecus bahrelghazali, une nouvelle espèce d'Hominidé ancien de la région de Koro Toro (Tchad). In: Comptes Rendus de l'Academie de Sciences - Series IIa: Sciences de la Terre et des Planetes. Volume 322, No. 10, 1996, pp. 907–913, full text (PDF)
  2. ↑ Michel Brunet et al .: The first australopithecine 2,500 kilometers west of the Rift Valley (Chad). In: Nature . Volume 378, 1995, pp. 273-275, doi: 10.1038 / 378273a0
  3. ^ Ann Gibbons: Profile: Michel Brunet. One Scientist's Quest for the Origin of Our Species. In: Science . Volume 298, No. 5599, 2002, pp. 1708-1711, doi: 10.1126 / science.298.5599.1708
  4. ↑ Bernard Wood , Nicholas Lonergan: The hominin fossil record: taxa, grades and clades. In: Journal of Anatomy . Volume 212, No. 4, 2008, p. 358, doi: 10.1111 / j.1469-7580.2008.00871.x , full text (PDF; 292 kB) ( Memento from October 29, 2013 in the Internet Archive )
  5. ↑ a b Julia Lee-Thorp et al .: Isotopic evidence for an early shift to C 4 resources by Pliocene hominins in Chad. In: PNAS. Volume 109, No. 50, 2012. pp. 20369-20372, doi: 10.1073 / pnas.1204209109
    Human Ancestors Were Grass Gourmands. With a picture of the lower jaw. On: sciencemag.org of November 12, 2012
  6. ↑ Anne-Elisabeth Lebatard et al .: Cosmogenic nuclide dating of Sahelanthropus tchadensis and Australopithecus bahrelghazali: Mio-Pliocene hominids from Chad. In: PNAS . Volume 105, No. 9, 2008, pp. 3226-3231, doi: 10.1073 / pnas.0708015105
  7. ↑ Alain Beauvilain: The contexts of discovery of Australopithecus bahrelghazali (Abel) and of Sahelanthropus tchadensis (Toumaï): unearthed, embedded in sandstone, or surface collected? In: South African Journal of Science. Volume 104, No. 5–6, 2008, pp. 165–168, full text (PDF; 491 kB)