Quote: Encyclopedia of Human Evolution and Prehistory: Second Edition
Of three hominid specimens from the Chemeron Formation, all most probably hominins, one derives from the older, Tabarin outcrops dated between 5 and 4.15 Ma. This specimen is one of the earliest well-documented hominins in the fossil record; only the specimens from Lothagam, near Lake Turkana, are a little older. The Tabarin specimen is a piece of right mandible with intact first and second molars. In its dental features and details of subocclusal and mandibular morphology, it closely resembles smaller specimens of Australopithecus afarensis and also (as A. hill has pointed out) the more fragmentary material that has been assigned to Australopithecus anamensis and Ardipithecus ramidus. W. Ferguson has named the Tabarin jaw Homo antiquus praegens, which might have priority if this specimen is conspecific with either anamensis or ramidus. The other early Chemeron specimen, from a site some kilometers to the north of Tabarin, is a proximal fragment of a humerus that seems likely to represent the same species as that of the Tabarin mandible. The third hominin, from the upper part of the Chemeron, is much younger than the other occurences, dating close to 2.4 Ma. This is a temporal bone that comes from a site on the Kapthurin River near its mouth on Lake Baringo. After languishing as Hominidae indeterminate, it has been reanalyzed and identified as Homo sp. indet. (cf. H. rudolfensis?), one of the three earliest representatives of the genus Homo, the others being from Hadar (Ethiopia) and Uraha (Malawi). An older site, near the base of the Upper Chemeron, yielded a partial skeleton of Paracolobus chemeroni (the type) and a partial skull of ?Theropithecus (Omopithecus) baringensis (also the type); these fossils remained undated for many years, but they are now closely estimated to date to 3.1-3 Ma.