The oldest Camelidae (Mammalia, Artiodactyla) of Africa: new finds from the Mio-Pliocene boundary, Chad

摘要: A fragment of mandible and two metapodials complete unearthed from the fossiliferous aera Kossom Bougoudi (KB3 KB26), northern Chad are described. comparative study allows to assign these specimens Paracamelus gigas . The evolutionnary degree is compatible with an age around Mio-Pliocene boundary (ca 5 Ma). Then, Chadian remains oldest adequately dated record this family in Africa. They contemporaneous known evidence genus late Miocene Asia Europe. Introduction. – During several field seasons Chad, “Mission Paleoanthropologique Franco-Tchadienne” (M. P. F. T) discovered new sites (KB) area, west australopithecine [Brunet et al., 1995, 1997; Brunet M.P.F.T, 2000]. These yielded a rich vertebrate fauna (fish, reptiles, birds mammals), have been biochronologically at Ma old, close M. F.T, Among mammal fauna, some Camelidae provide earliest group Africa, which was previously thought be younger than 4 Ma, Laetoli [Harris, 1987] Koobi Fora 1991]. Specimens KB3 KB26 described here. Description Material : KB3.97.316 right p 3 , -m 1 roots m 2 teeth; KB3.99.03 metatarsus; KB26.97.03 metatarsus rather robust high horizontal ramus. mental foramen located below alveolus attest elongated premolars. lingual face molars flat. third lobe less labially shifted living camels. There no cement, nor cingulum. metatarsals long (tab. III), show deep groove on proximal anterior posterior faces. distal condyles divergent separated by interarticular notch. symmetrical same size differences, contrast extant species where external condyle more slender internal one. Comparison (KB3.97.316) differs Camelus having (1) deeper ramus, (2) well developed (3) (4) morphologically different those camels being extremely II). All characters congruent Zdansky’s [1926] Teilhard Trassaert’s [1937] descriptions KB ramus that alutensis I) early Pleistocene Oltet Valley, Romania [Stefanescu, 1910]. premolar row longer. Unfortunately, detailed comparison aguirrei (MN13) Venta del Moro Librilla, Spain impossible because defined skeletal elements (upper molars, calcaneum, phalanxes) not yet recovered Chad. However, estimated alveolar length (20 mm) similar (18,8 21,6 mm according Morales [1984]). Lengths tooth II) fit into range variation recorded Zdansky Trassaert for China. material cannot assigned alexejevi Pliocene (MN15) Ukraine, smaller [Morales, 1984]. In conclusion, do display any important difference Chinese can tentatively referred species. Biochronology paleobiogeography. Old World camel correspond Librilla [Morales al. 1980; Made Morales, 1999]. After [1999], probably ancestor Odessa Catacombs (MN15), Ukraine. Europe, chronological covers Plio-Pleistocene. This present lower 1910] Middle (MN16) Russia [Baigusheva, 1971]. It also Sarikol Tepe, Turkey [Kostopoulos Sen, China, about 5.5 [Flynn, conclusion Pleistocene. (first occurrence China Ma) its absence (3-4 Koro-Toro Kolle 1995; 1996] as Plio-Pleistocene localities KB. interpretation confirmed associated indicates ca old whole area boundary, slightly [Zdansky, 1926; Flynn, 1997], 1980] [Made 2002]. demonstrates had wider distribution thought. reach widespread soon after their arrival America [Webb, 1965; Pickford 1993]. Conclusion. displays distinctive features refer it taxon, poorly documented Eurasia, has recognised will contribute deciphering phylogenetic relationships between various