Hidemi Ishida

A new Late Miocene hominoid from Kenya: Samburupithecus kiptalami gen. et sp. nov.

Abstract A new genus and species of hominoid, Samburupithecus kiptalami , is erected on the basis of a maxillary specimen with complete post canine dentition. Its age is established as upper Miocene (9.5 Ma) on the basis of radioisotopic dating and associated mammalian fauna. The new genus is more closely related to the African ape —human clade (AAH) than is any other known extinct hominoid and it may well be on the line leading to hominids.

Human Origins and Environmental Backgrounds.

Hidemi Ishida: 40 Years of Footprints in Japanese Primatology and Paleoanthropology.- Hidemi Ishida: 40 Years of Footprints in Japanese Primatology and Paleoanthropology.- Fossil Hominoids and Paleoenvironments.- Seven Decades of East African Miocene Anthropoid Studies.- Evolution of the Vertebral Column in Miocene Hominoids and Plio-Pleistocene Hominids.- Terrestriality in a Middle Miocene Context: Victoriapithecus from Maboko, Kenya.- Late Cenozoic Mammalian Biostratigraphy And Faunal Change.- The Ages and Geological Backgrounds of Miocene Hominoids Nacholapithecus, Samburupithecus, and Orrorin from Kenya.- Functional Morphology.- Patterns of Vertical Climbing in Primates.- Functional Morphology of the Midcarpal Joint in Knuckle-Walkers and Terrestrial Quadrupeds.- Morphological Adaptation of Rat Femora to Different Mechanical Environments.- A Hallmark of Humankind: The Gluteus Maximus Muscle.- Primates Trained for Bipedal Locomotion as a Model for Studying the Evolution of Bipedal Locomotion.- Locomotor Energetics in Nonhuman Primates.- Computer Simulation of Bipedal Locomotion.- Theoretical Approaches.- Paleoenvironments, Paleoecology, Adaptations, and the Origins of Bipedalism in Hominidae.- Arboreal Origin of Bipedalism.- Neontological Perspectives on East African Middle and Late Miocene Anthropoidea.- The Prehominid Locomotion Reflected: Energetics, Muscles, and Generalized Bipeds.- Evolution of the Social Structure of Hominoids.- Are Human Beings Apes, or are Apes People too?.- Current Thoughts on Terrestrialization in African Apes and the Origin of Human Bipedalism.

K-Ar ages of miocene hominoidea (Kenyapithecus and Samburupithecus) from Samburu Hills, Northern Kenya

The Neogene volcano-sedimentary succession west of Baragoi and in the Samburu Hills, northern Kenya has yielded over 200 higher primate fossils, comprising the cercopithecoid Victoriapithecus and the hominoids, Nyanzapithecus, Kenyapithecus and Samburupithecus. K-Ar ages have been obtained from lavas and pumices intercalated with the sediments. The Aka Aiteputh Formation with Kenyapithecus and Nyanzapithecus is dated ca 15-14 Ma while the Namurungule Formation with Samburupithecus is ca 9.5 Ma.

The Late Miocene Large Mammal Fauna from the Namurungule Formation, Samburu Hills, Northern Kenya

By the Japan-Kenya Expedition, more than 1145 late Miocene vertebrate fossils were collected from the Namurungule Formation in Samburu Hills, Northern Kenya in 1982. These fossils are assigned to at least 29 taxa of which 21 are mammals, including Hominoid, Tetralophodon, two kinds of Hipparion, Brachypotherium, Kenyapotamus, and Pachytragus. Quantitatively, the taxa of Hipparion are the most predominant. But gomphothere, bovid, rhinocerotid and giraffid fossils are approximately as common as each other at Namurungule. Suids, hippopotamids and carnivores seem to be unifonnly rare as fossils at Samburu. In this paper, 19 taxa of mammals are described and discussed briefly. The Namurungule mammalian fauna is closer in age to Ngorora (c. 11 m.y.) than to Mpesida (7 m.y.) from Kenya, and this fauna is similar to the faunas of Samos and Pikermi (Vallesian). It seems that the abundance of Hipparion, giraffids, rhinocerotids and bovids suggests a woodland to savannah environment at or near Namurungule during the upper Miocene. We find very little evidence to suggest that there was forest in the vicinity at the time of deposition.

Dynamics of primate bipedal walking as viewed from the force of foot

Bipedal walking of the six species of anthropoid primates including man were examined by means of the force plate technique. Though each species has a particular pattern of bipedal walking, we can classify two types of patterns in these primates as far as the foot force is concerned. The first type includes the man, chimpanzee, and spider monkey and the second type contains the Japanese monkey, hamadryas baboon, and gibbon. It was emphasized that the similarity of man to the chimpanzee and spider monkey in bipedal walking has some evolutionary significance.

FOSSIL ANTHROPOIDS FROM NACHOLA AND SAMBURU HILLS, SAMBURU DISTRICT, KENYA

During the 1982 expedition to Samburu Hills and Nachola, a number of hominoid fossils was found from two Miocene deposits. A small hominoid and a large late Miocene hominoid are contained in the fossils. The former most closely resembles Kenyapithecus africanus, and the latter may be ancestral to the extant African apes and hominoids, to gorilla alone, or not to any living hominoids. The various alternatives are discussed.

Preliminary analysis of Nacholapithecus scapula and clavicle from Nachola, Kenya

The Miocene ape Nacholapithecus is known from rather complete skeletons; some of them preserve the shoulder joint, identified by three scapulae and one clavicle. Comparisons made with other Miocene and living apes (Proconsul, Equatorius, Ugandapithecus) suggest that the mobility of the scapulohumeral joint was important, and scapular features such as the morphology and position of the spine and the morphology of the acromion and axillary border resemble those of climbing arboreal primates except for chimpanzees, gorillas, or orang-utans. From the size of the scapula (male Nasalis size), it is clear that the animal is smaller than an adult chimpanzee, but the clavicle is almost as relatively long as those of chimpanzees. Some features closer to colobine morphology reinforce the hypothesis that Nacholapithecus was probably a good climber and was definitely adapted for an arboreal life.

Interpretation of Samburupithecus, an Upper Miocene hominoid from Kenya

Samburupithecus, an extinct great ape from upper Miocene (9.5 Ma) deposits in Kenya, is compared with other fossil and extant hominoids. It possesses features which are derived in comparison with Proconsul and other Lower and Middle Miocene hominoids, but it has none of the derived features which characterize the Eurasian large apes. It possesses characters which indicate that its closest relationships lie with the AAH clade (extant African apes and man). Within this clade it is closest dentally to primitive hominids such as Praeanthropus.

Fossiliferous Localities of the Nachola-Samburu Hills Area, Northern Kenya

In the four geographic/stratigraphic areas of the Samburu Hills and Nachola. west of Baragoi, Kenya. a significant number of fossiliferous localities was found. Nachola area is dated to the middle Miocene, the Namurungule Formation in Samburu Hills to the upper Miocene, Kongia area (0 the Mio-Pliocene and Holocene to the area near Suguta Valley and in the drainage systems of the Samburu Hills to the Holocene. The site BG X in Nachola yielded a number of fossils provisionally assigned to Kenyapitlzecus. An important large hominoid specimen occurred in Site SH n of the Namurungule Fonnation. Undoubtedly a great many additional sites await discovery.

Climate shift recorded at around 10 Ma in Miocene succession of Samburu Hills, northern Kenya Rift, and its significance

Abstract A significant climate shift around 9.6 Ma has been detected from the Middle to Upper Miocene Aka Aiteputh and Namurungule Formations exposed in the Samburu Hills, northern Kenya. Around 9.6 Ma, changes in sediments are recorded from the red soil-dominated interval of the upper Aka Aiteputh Formation to the lacustrine and deltaic facies of the lower Namurungule Formation, containing open woodland/savanna mammalian fauna. These reveal a shift from a dry climate with seasonal precipitation to a climate with strong seasonality. In particular, an increase in precipitation was recorded by the predominance of lacustrine facies. This shift happened at around the same time as the intensification of the Indian summer monsoon that has been detected in the Himalayas and some of surrounding regions. There are two scenarios that could explain the increased precipitation at the beginning of the deposition of the Namurungule Formation: (1) enhanced moisture transport by the Intertropical Convergence Zone (ITCZ), synchronized with Indian summer monsoon intensification, or (2) intensification of the Indian summer monsoon itself, permitting moisture to penetrate deep into East Africa if the altitude of the rifted area was lower than it is now. Presently, the former is considered to be the more plausible explanation for the climate shift detected in the Samburu Hills.