New femoral remains of <i>Nacholapithecus kerioi</i>: Implications for intraspecific variation and Miocene hominoid evolution

The middle Miocene stem kenyapithecine Nacholapithecus kerioi (16-15 Ma; Nachola, Kenya) is represented by a large number of isolated fossil remains and one of the most complete skeletons in the hominoid fossil record (KNM-BG 35250). Multiple fieldwork seasons performed by Japanese-Kenyan teams during the last part of the 20th century resulted in the discovery of a large sample of Nacholapithecus fossils. Here, we describe the new femoral remains of Nacholapithecus. In well-preserved specimens, we evaluate sex differences and within-species variation using both qualitative and quantitative traits. We use these data to determine whether these specimens are morphologically similar to the species holotype KNM-BG 35250 (which shows some plastic deformation) and to compare Nacholapithecus with other Miocene hominoids and extant anthropoids to evaluate the distinctiveness of its femur. The new fossil evidence reaffirms previously reported descriptions of some distal femoral traits, namely the morphology of the patellar groove. However, results also show that relative femoral head size in Nacholapithecus is smaller, relative neck length is longer, and neck-shaft angle is lower than previously reported for KNM-BG 35250. These traits have a strong functional signal related to the hip joint kinematics, suggesting that the morphology of the proximal femur in Nacholapithecus might be functionally related to quadrupedal-like behaviors instead of more derived antipronograde locomotor modes. Results further demonstrate that other African Miocene apes (with the exception of Turkanapithecus kalakolensis) generally fall within the Nacholapithecus range of variation, whose overall femoral shape resembles that of Ekembo spp. and Equatorius africanus. Our results accord with the previously inferred locomotor repertoire of Nacholapithecus, indicating a combination of generalized arboreal quadrupedalism combined with other antipronograde behaviors (e.g., vertical climbing)

FOSSIL MAMMALS FROM THE NEOGENE STRATA IN THE SINDA BASIN< EASTERN ZAIRE

Since 1989, a geological and paleontological expedition has been carried out in the Zairean part of the Western Rift Valley. During two field seasons, more than 600 fossil remains were collected in the Sinda basin, Gaty, Haut-Zaire, mainly as surface finds. This fossil collection contains 52 mammalian fossils which comprise the following taxa; ? Agriotherium, four proboscidean groups such as Prodeinotherium, ?Anancus, Mammuthus subplanifrons and Stegodon kaisensis, two Rhinocerotidae, i.e., ?Aceratherium and Brachypotherium, ?Sivatherium, Hippopotamus, and a bovid. The Sinda fauna is composed of both Miocene and Pliocene mammals and suggest that the strata including the fossils are of late Miocene to early Pliocene in age. This fauna resembles that from the Nkondo formation which is located in the Ugandan side of the Western Rift Valley. The composition of the fauna from the Sinda area may indicate a different paleoenvironment (probably more humid) in this area from that in contemporary East Africa. RESUME Depuis 1989, une expedition geologique et paleontologique est realisee dans la partie zairoise de la branche occidentale du Rift. Durant deux saisons, plus de 600 restes fossiles ont ete collectele basin de Sinda, Gaty, haut-za?re, principalement comme decouvertes de surface. Cette collection fossile contient 52 mammiferes fossiles qui comprennent les taxa suivant; ?Agriotherium, qutre groupes proboscidean tels que Prodeinotherium, ?Anancus, Mammuthus subplanifrons et Stegodon kaisensis, deux Rhinocerotidae par exemple, ?Aceratherium et Brachypotherium, ?Sivathrium, Hippopotamus, et un bovide. La faune de Sinda est composee des mammiferes du miocene et du pliocene et suggere que le strate inclus les fossils sont de l'age du miocene superieur au debut pliocene Cette faune ressemble celle de Nkondo formation qui est situee dans la partie ougandaise du Rift Occidental. La composition de la faune de l'aire de Sinda devra indique un paleoencironement different (probablement plus humide) dans cette aire de celui en l'est-aficain contemporain

New femoral remains of Nacholapithecus kerioi: Implications for intraspecific variation and Miocene hominoid evolution

The middle Miocene stem kenyapithecine Nacholapithecus kerioi (16-15 Ma; Nachola, Kenya) is represented by a large number of isolated fossil remains and one of the most complete skeletons in the hominoid fossil record (KNM-BG 35250). Multiple fieldwork seasons performed by Japanese-Kenyan teams during the last part of the 20th century resulted in the discovery of a large sample of Nacholapithecus fossils. Here, we describe the new femoral remains of Nacholapithecus. In well-preserved specimens, we evaluate sex differences and within-species variation using both qualitative and quantitative traits. We use these data to determine whether these specimens are morphologically similar to the species holotype KNM-BG 35250 (which shows some plastic deformation) and to compare Nacholapithecus with other Miocene hominoids and extant anthropoids to evaluate the distinctiveness of its femur. The new fossil evidence reaffirms previously reported descriptions of some distal femoral traits, namely the morphology of the patellar groove. However, results also show that relative femoral head size in Nacholapithecus is smaller, relative neck length is longer, and neck-shaft angle is lower than previously reported for KNM-BG 35250. These traits have a strong functional signal related to the hip joint kinematics, suggesting that the morphology of the proximal femur in Nacholapithecus might be functionally related to quadrupedal-like behaviors instead of more derived antipronograde locomotor modes. Results further demonstrate that other African Miocene apes (with the exception of Turkanapithecus kalakolensis) generally fall within the Nacholapithecus range of variation, whose overall femoral shape resembles that of Ekembo spp. and Equatorius africanus. Our results accord with the previously inferred locomotor repertoire of Nacholapithecus, indicating a combination of generalized arboreal quadrupedalism combined with other antipronograde behaviors (e.g., vertical climbing)

Variation of bony labyrinthine morphology in Mio−Plio−Pleistocene and modern anthropoids

Objectives The bony labyrinth of the inner ear has special relevance when tracking phenotypic evolution because it is often well preserved in fossil and modern primates. Here we track the evolution of the bony labyrinth of anthropoid primates during the Mio−Plio−Pleistocene—the time period that gave rise to the extant great apes and humans. Materials and Methods We use geometric morphometrics to analyze labyrinthine morphology in a wide range of extant and fossil anthropoids, including New World and Old World monkeys, apes, and humans; fossil taxa are represented by Aegyptopithecus, Microcolobus, Epipliopithecus, Nacholapithecus, Oreopithecus, Ardipithecus, Australopithecus, and Homo. Results Our results show that the morphology of the anthropoid bony labyrinth conveys a statistically significant phylogenetic signal especially at the family level. The bony labyrinthine morphology of anthropoids is also in part associated with size, but does not cluster by locomotor adaptations. The Miocene apes examined here, regardless of inferred locomotor behaviors, show labyrinthine morphologies distinct from modern great apes. Discussion Our results suggest that labyrinthine variation contains mixed signals and alternative explanations need to be explored, such as random genetic drift and neutral phenotypic evolution, as well as developmental constraints. The observed pattern in fossil and extant hominoids also suggests that an additional factor, for example, prenatal brain development, could have potentially had a larger role in the evolutionary modification of the bony labyrinth than hitherto recognized