Sahelanthropus tchadensis is an extinct hominid species that is dated to about 7 ẹgbẹgbẹ̀rún ọdún sẹ́yìn. Whether it can be regarded as part of the Hominina tree is unclear; there are arguments both supporting and rejecting it. Another complication in its classification is that it is older than the human-chimpanzee divergence (estimated to 6.3 to 5.4 ẹgbẹgbẹ̀rún ọdún sẹ́yìn) seen in genetic data, and that there are few if any specimens other than the partial cranium known as Toumaï. Usually, all authors of a taxon description are cited. In this case they are so many however that for layout reasons the list is abbreviated. The full citation is: Brunet, Guy, Pilbeam, Mackaye, Likius, Ahounta, Beauvilain, Blondel, Bocherens, Boisserie, De Bonis, Coppens, Dejax, Denys, Duringer, Eisenmann, Fanone, Fronty, Geraads, Lehmann, Lihoreau, Louchart, Mahamat, Merceron, Mouchelin, Otero, Pelaez Campomanes, Ponce de León, Rage, Sapanet, Schuster, Sudre, Tassy, Valentin, Vignaud, Viriot, Zazzo, & Zollikofer, 2002.