New partial skeleton of Homo habilis from the upper Burgi Member, Koobi Fora Formation, Ileret, Kenya

KNM-ER 64061 is a partial skeleton from the upper Burgi Member of the Koobi Fora Formation (2.02-2.06 Ma) associated taphonomically and geochemically with a nearly complete mandibular dentition (KNM-ER 64060) attributed to Homo habilis. The skeleton comprises the clavicle, scapular fragments, both humeri, both ulnae, both radii, and a fragmentary sacrum and os coxae, making this the most complete H. habilis skeleton recovered thus far. The upper limb elements are similar to those of other early Homo specimens. Notably, the humerus is slender with a weakly-projecting lateral epicondyle, a relatively wide capitulum and a narrow trochlea, and the ulna has a relatively large radial notch. Although KNM-ER 64061 does not preserve a lower limb, limited features of the ischium suggest lower limb mechanics more similar to Homo than to australopiths. Brachial index estimates support previous conclusions that H. habilis had a relatively long forearm compared to Homo erectus. All upper limb elements possess strikingly thick cortices, resembling the condition in australopiths and other early Homo fossils. The stature estimate of 160 cm based on humeral length is intermediate between those for H. habilis (OH 62, KNM-ER 3735) and H. erectus (KNM-ER 1808, KNM-WT 15000). The body mass estimate of 30.7-32.7 kg is slightly lower than other H. habilis specimens and noticeably lower than estimates for H. erectus. KNM-ER 64061 indicates that H. habilis retained more primitive proportions and was smaller in stature and mass than H. erectus.