New fossils from Koobi Fora in northern Kenya confirm taxonomic diversity in early Homo.

Since its discovery in 1972 (ref. 1), the cranium KNM-ER 1470 has been at the centre of the debate over the number of species of early Homo present in the early Pleistocene epoch of eastern Africa. KNM-ER 1470 stands out among other specimens attributed to early Homo because of its larger size, and its flat and subnasally orthognathic face with anteriorly placed maxillary zygomatic roots. This singular morphology and the incomplete preservation of the fossil have led to different views as to whether KNM-ER 1470 can be accommodated within a single species of early Homo that is highly variable because of sexual, geographical and temporal factors, or whether it provides evidence of species diversity marked by differences in cranial size and facial or masticatory adaptation. Here we report on three newly discovered fossils, aged between 1.78 and 1.95 million years (Myr) old, that clarify the anatomy and taxonomic status of KNM-ER 1470. KNM-ER 62000, a well-preserved face of a late juvenile hominin, closely resembles KNM-ER 1470 but is notably smaller. It preserves previously unknown morphology, including moderately sized, mesiodistally long postcanine teeth. The nearly complete mandible KNM-ER 60000 and mandibular fragment KNM-ER 62003 have a dental arcade that is short anteroposteriorly and flat across the front, with small incisors; these features are consistent with the arcade morphology of KNM-ER 1470 and KNM-ER 62000. The new fossils confirm the presence of two contemporary species of early Homo, in addition to Homo erectus, in the early Pleistocene of eastern Africa.

A new skeleton of Theropithecus brumpti (Primates: Cercopithecidae) from Lomekwi, West Turkana, Kenya.

A relatively complete skeleton of the fossil papionin, Theropithecus brumpti, from the site of Lomekwi, west of Lake Turkana, Kenya, is here described. The specimen, KNM-WT 39368, was recovered at the site of LO 5 (3 degrees 51'N and 35 degrees 45'E), from sediments dated to approximately 3.3Ma. The skeleton is that of an old adult male and preserves a number of articulated elements, including most of the forelimbs and tail. The cranial morphology is that of a large, early T. brumpti, exhibiting a deep mandible with a deeply excavated mandibular corpus fossa, and mandibular alveoli and cheek teeth arrayed in a reversed Curve of Spee. The forelimb skeleton exhibits a unique mixture of characteristics generally associated with a terrestrial locomotor habitus, such as a narrow scapula and a highly stable elbow joint, combined with those more representative of habitual arborealists, such as muscle attachments reflecting a large rotator cuff musculature and a flexible shoulder joint. The forelimb of KNM-WT 39368 also presents several features, unique toTheropithecus, which represent adaptations for manual grasping and fine manipulation. These features include a large, retroflexed medial humeral epicondyle (to which large pronator, and carpal and digital flexor muscles attached) and proportions of the digital rays that denote capabilities for precise opposition between the thumb and index finger. Taken together, these features indicate that one of the earliest recognized representatives of Theropithecus exhibited the food harvesting and processing anatomy that distinguished the genus through time and that contributed to its success throughout the later Pliocene and Pleistocene. Based on the anatomy of KNM-WT 39368 and the known habitat preference of T. brumpti, the species is reconstructed as being a generally terrestrial but highly dexterous, very large-bodied, sexually dimorphic, and possibly folivorous papionin. T. brumpti was adapted for propulsive quadrupedal locomotion over generally even ground, and yet was highly adept at manual foraging. The estimate of 43.8kg body mass for KNM-WT 39368 renders unlikely the possibility that the species, or at least adult males of the species, were highly arboreal. T. brumpti, as represented by KNM-WT 39368, is seen as a large, colorfully decorated, and basically terrestrial papionin that was restricted to riverine forest habitats in the Lake Turkana Basin from the middle to latest Pliocene.