FIRST HOMINOID FROM THE MIOCENE OF ETHIOPIA AND THE EVOLUTION OF THE CATARRHINE ELBOW

The first known fossil ape from the early-middle Miocene of Fejej, Eth iopia, is described here. The specimen, FJ-18SB-68, is a partial ulna from a locality dated by Ar-40/Ar-39 and paleomagnetic methods to a mi nimum age of 16.18 MYA. Compared to a variety of extant and fossil uln ae, FJ-18SB-68 is most similar to Turkanapithecus, Proconsul, and Plio pithecus, and appears to have been an arboreal quadruped with substant ial forearm rotational mobility. Among the extant ulnae, canonical var iates analysis successfully discriminates platyrrhines from catarrhine s and within the latter, cercopithecoids from hominoids. Basal catarrh ines (e.g., Aegyptopithecus) are platyrrhine-like in their morphology. Two basic trends appear to evolve from this generalized template: one with less mobile and more habitually pronated forearms, as seen in li ving and fossil cercopithecoids (including Victoriapithecus and Paraco lobus), and another with greater forearm rotational mobility in fossil and modern hominoids. Primitive Miocene apes, including Proconsul, Tu rkanapithecus, and FJ-18SB-68, share with extant hominoids a more late rally positioned and laterally facing radial notch and an incipient tr ochlear keel. This morphology, along with a large insertion area for m . brachialis, suggests a departure from the more habitually pronated h and posture of monkeys and may indicate greater climbing abilities in these arboreally quadrupedal apes. Later Miocene apes, such as Oreopit hecus and Dryopithecus share additional morphological features with ho minoids, indicating considerable suspensory and climbing capabilities. (C) 1998 Wiley-Liss, Inc.