Jaw mandible, Australopithecus anamensis
This jaw mandible is part of a collection of A. anamensis fossils discovered in 1994 by Maeve Leakey in Kanapoi and Alia Bay. It was named Australopithecus anamensis from "anam" meaning "lake" in the local Turkana language. The fossils (9 from Kanapoi and 12 from Alia Bay) include upper and lower jaws, cranial fragments, and the upper and lower parts of a leg bone (tibia). In addition to this, the collection includes a fragment of humerus that was found 30 years ago at the same site at Kanapoi.
The Kanapoi fossils have been dated at 4.2 million years and those at Alia Bay at 3.9 million years. The dentition is less apelike than in Ardipithecus ramidus (Australopithecus ramidus, found in Ethiopia), having thick enamel on the molar teeth but relatively large canines. The tibia implies that A. anamensis was larger than A. ramidus and A. afarensis, with an estimated weight of 46 to 55 kilograms; its humanlike anatomy implies that A. anamensis was bipedal in posture and locomotion. Although distinct from Australopithecus afarensis, its discoverers claim that Australopithecus anamensis resembles the Laetoli fossils more than those found in Hadar. The discovery of this species pushed bipedal walking back half a million years. Facially this species resembles A. afarensis a lot, it is very apelike.
It was found along the East African Rift valley and due to the dating of this hominine species, Australopithecus anamensis could possibly be an ancestor to "Lucy" and counterparts.
Credit: photo and (edited) text courtesy of Lorraine Dallmeier. Her website, PaleoAnthropology: A Short Journey Through Time, offers a superb introduction to the subject.