TM 266
TM 266 is the name of a site of Upper Miocene fossils in the Djurab desert in northern Chad , which has been researched since 1997 . The abbreviation TM stands for the Toros-Menalla hominid locality , an area in which more than 300 sites have been discovered. The most important find from the approximately 5000 square meter excavation site was recovered between July 2001 and February 2002: the holotype of the genus Sahelanthropus .
Starting in 1994, the Mission Paléoanthropologique Franco-Tchadienne , founded by Michel Brunet , a cooperation between the University of Poitiers , the University of N'Djamena and the Center National d'Appui à la Recherche (CNAR, N'Djamena ), carried out various field studies in the Djurab desert carried out in the Chad Basin . Dozens of superficial sites for Miocene and Pliocene vertebrate fossils were discovered, each of which was biochronologically dated. In addition to TM 266 (7–6 mya ), the KT 12 (3.5–3.0 mya) site at Koro Toro was also developed, as well as the Kollé (5–4 mya) and Kossom Bougoudi (approx. 5.3 mya). In site 266 alone, fossils of more than 40 vertebrate species were recovered, more than half of which came from mammals .
Among other things, the remains of more than ten species of freshwater fish (including a predatory fish from the genus Hydrocynus , also Polypterus , Gymnarchus and Labeo ), amphibians , crocodiles ( Euthecodon ) and turtles , but also bones of slippery monkeys and colobus monkeys were identifiable , of rodents ( Xerus sp. and murinae ), elephants , sivatherium ( Sivatherium ), horses ( Hipparion ), pigs ( Nyanzachoerus ), antelopes and cattle . Fossil hyenas have been excavated as the most common predators (both in terms of the number of individuals found and the number of species) . Almost all fish found have related species in today's Lake Chad , some of the fossil fish were longer than one meter; Bird species were absent from the fossilized layers.
Based on the known change in shape in the course of the evolution of the teeth of Nyanzachoerus and taking into account comparable findings on the evolution of the teeth of other mammalian groups ( Anthracotheriidae , proboscis , horses and cattle), the age of the TM 266 was narrowed down to 7 to 6 million years. The composition of the species was interpreted in such a way that these animals - among them Sahelanthropus tchadensis - lived "near a lake, but not far from a sandy desert "; Signs of rich sand deposits were above all meter-high fossil dunes with well-preserved ripple marks . The researchers also interpreted the evidence of cattle, for example, as an indication of neighboring open savannahs , of giraffes and proboscis to more heavily forested savannahs and of monkeys to gallery forests .
The researchers pointed out that similar biotopes as for Sahelanthropus were also reconstructed for Orrorin and Ardipithecus .
The holotype of Australopithecus bahrelghazali was also found in the north of Chad - at the site KT 12 .
Web links
- Some photos from the Djurab desert (PDF; 266 kB)
Individual evidence
- ↑ Patrick Vignaud et al .: Geology and palaeontology of the Upper Miocene Toros-Menalla hominid locality, Chad. In: Nature. Volume 418, 2002, pp. 152-155, doi: 10.1038 / nature00880