Correlation between musculoskeletal structure of the hand and primate locomotion: Morphometric and mechanical analysis in prehension using the cross- and triple-ratios.

Biometric ratios of the relative length of the rays in the hand have been analyzed between primate species in the light of their hand function or phylogeny. However, how relative lengths among phalanges are mechanically linked to the grasping function of primates with different locomotor behaviors remains unclear. To clarify this, we calculated cross and triple-ratios, which are related to the torque distribution, and the torque generation mode at different joint angles using the lengths of the phalanges and metacarpal bones in 52 primates belonging to 25 species.

The extinct river shark Glyphis pagoda from the Miocene of Myanmar and a review of the fossil record of the genus Glyphis (Carcharhiniformes: Carcharhinidae).

We redescribe an extinct river shark, Glyphis pagoda (Noetling), on the basis of 20 teeth newly collected from three different Miocene localities in Myanmar. One locality is a nearshore marine deposit (Obogon Formation) whereas the other two localities represent terrestrial freshwater deposits (Irrawaddy sediments), suggesting that G. pagoda from the Irrawaddy sediments was capable of tolerating low salinity like the extant Glyphis.

First discovery of colobine fossils from the Late Miocene/Early Pliocene in central Myanmar.

Here we report two kinds of colobine fossils discovered from the latest Miocene/Early Pliocene Irrawaddy sediments of the Chaingzauk area, central Myanmar. A left mandibular corpus fragment preserving M1-3 is named as a new genus and species, Myanmarcolobus yawensis. Isolated upper (M(1)?) and lower (M2) molars are tentatively identified as Colobinae gen.

Prenatal ontogeny of subspecific variation in the craniofacial morphology of the Japanese macaque (Macaca fuscata).

We cross-sectionally investigated prenatal ontogeny of craniofacial shape in the two subspecies of the Japanese macaque (Macaca fuscata fuscata and Macaca fuscata yakui) using a geometric morphometric technique to explore the process of morphogenetic divergence leading to the adult morphological difference between the subspecies. The sample comprised a total of 32 formalin-fixed fetal specimens of the two subspecies, in approximately the second and third trimesters. Each fetal cranium was scanned using computed tomography to generate a three-dimensional surface model, and 68 landmarks were digitized on the external and internal surface of each cranium to trace the growth-related changes in craniofacial shape of the two subspecies.

Femur length, body mass, and stature estimates of Orrorin tugenensis, a 6 Ma hominid from Kenya.

To understand the palaeobiology of extinct hominids it is useful to estimate their body mass and stature. Although many species of early hominid are poorly preserved, it is occasionally possible to calculate these characteristics by comparison with different extant groups, by use of regression analysis. Calculated body masses and stature determined using these models can then be compared.

Additional materials of Myanmarpithecus yarshensis (Amphipithecidae, Primates) from the middle Eocene Pondaung Formation.

Myanmarpithecus yarshensis is an amphipithecid primate from the middle Eocene Pondaung Formation in Myanmar. It was previously known based on maxillary fragments with P(4)-M(3) and mandibular fragments with C-P(3) and M(2-3). This study reports new materials for the genus, including a humeral head fragment, a lingual fragment of the right M(2), a lingual fragment of the right M(3), and a left I(1).

Variation in maxillary sinus anatomy among platyrrhine monkeys.

Variations in the maxillary sinus anatomy of extant and fossil catarrhine primates have been extensively examined using computed tomography (CT), and have potential utility for phylogenetic analyses. This approach has also been used to demonstrate its anatomical variation in eight of the 16 extant genera of platyrrhines and the absence of the sinus in Saimiri and Cacajao. We used this approach to evaluate the three-dimensional anatomy of the maxillary sinus in all extant platyrrhine genera, and here argue the phylogenic implications of this variation.

The paleobiology of Amphipithecidae, South Asian late Eocene primates.

Analysis of the teeth, orbital, and gnathic regions of the skull, and fragmentary postcranial bones provides evidence for reconstructing a behavioral profile of Amphipithecidae: Pondaungia, Amphipithecus, Myanmarpithecus (late middle Eocene, Myanmar) and Siamopithecus (late Eocene, Thailand). At 5-8 kg, Pondaungia, Amphipithecus, and Siamopithecus are perhaps the largest known Eocene primates. The dental and mandibular anatomy suggest that large-bodied amphipithecids were hard-object feeders.

Endocranial cast and morphology of the olfactory bulb of Amphipithecus mogaungensis (latest middle Eocene of Myanmar).

A detailed endocranial cast of the olfactory bulb of Amphipithecus mogaungensis, a latest middle Eocene primate from the Pondaung Formation (Myanmar), was studied in comparison with some Paleogene primates, the olfactory bulb of which has been reported. The olfactory bulb of Amphipithecus is located just anterior to the postorbital constriction, that is, within the interorbital septum. It is relatively large and pedunculate, not overlapped by the frontal lobe, and consists of two parallel aligned bodies.