Primate postcrania from the late middle Eocene of Myanmar.

Fossil primates have been known from the late middle to late Eocene Pondaung Formation of Myanmar since the description of Pondaungia cotteri in 1927. Three additional primate taxa, Amphipithecus mogaungensis, Bahinia pondaungensis and Myanmarpithecus yarshensis, were subsequently described. These primates are represented mostly by fragmentary dental and cranial remains. Here we describe the first primate postcrania from Myanmar, including a complete left humerus, a fragmentary right humerus, parts of left and right ulnae, and the distal half of a left calcaneum, all representing one individual. We assign this specimen to a large species of Pondaungia based on body size and the known geographic distribution and diversity of Myanmar primates. Body weight estimates of Pondaungia range from 4,000 to 9,000 g, based on humeral length, humeral midshaft diameter, and tooth area by using extant primate regressions. The humerus and ulna indicate that Pondaungia was capable of a wide variety of forelimb movements, with great mobility at the shoulder joint. Morphology of the distal calcaneus indicates that the hind feet were mobile at the transverse tarsal joint. Postcrania of Pondaungia present a mosaic of features, some shared in common with notharctine and adapine adapiforms, some shared with extant lorises and cebids, some shared with fossil anthropoids, and some unique. Overall, Pondaungia humeral and calcaneal morphology is most consistent with that of other known adapiforms. It does not support the inclusion of Pondaungia in Anthropoidea.

Early Pleistocene 40Ar/39Ar ages for Bapang Formation hominins, Central Jawa, Indonesia.

The Sangiran dome is the primary stratigraphic window for the Plio-Pleistocene deposits of the Solo basin of Central Jawa. The dome has yielded nearly 80 Homo erectus fossils, around 50 of which have known findspots. With a hornblende (40)Ar/(39)Ar plateau age of 1.66 +/- 0.04 mega-annum (Ma) reportedly associated with two fossils [Swisher, C.C., III, Curtis, G. H., Jacob, T., Getty, A. G., Suprijo, A. & Widiasmoro (1994) Science 263, 1118-1121), the dome offers evidence that early Homo dispersed to East Asia during the earliest Pleistocene. Unfortunately, the hornblende pumice was sampled at Jokotingkir Hill, a central locality with complex lithostratigraphic deformation and dubious specimen provenance. To address the antiquity of Sangiran H. erectus more systematically, we investigate the sedimentary framework and hornblende (40)Ar/(39)Ar age for volcanic deposits in the southeast quadrant of the dome. In this sector, Bapang (Kabuh) sediments have their largest exposure, least deformation, and most complete tephrostratigraphy. At five locations, we identify a sequence of sedimentary cycles in which H. erectus fossils are associated with epiclastic pumice. From sampled pumice, eight hornblende separates produced (40)Ar/(39)Ar plateau ages ranging from 1.51 +/- 0.08 Ma at the Bapang/Sangiran Formation contact, to 1.02 +/- 0.06 Ma, at a point above the hominin-bearing sequence. The chronological sequence of (40)Ar/(39)Ar ages follows stratigraphic order across the southeast quadrant. An intermediate level yielding four nearly complete crania has an age of about 1.25 Ma.

Dietary consistency and craniofacial development related to masticatory function in minipigs.

Since the 1890s oral biological researchers have been interested in the idea that strenuous mastication of unprocessed food will stimulate proper oral-facial growth and occlusal relationships. Conversely, lack of such function due to consumption of refined food is one hypothesis among many for the etiology of malocclusion in industrialized humans. Adequately controlled experimental testing of the idea has been limited to rats. To investigate the "disuse" theory in a larger-bodied and more occlusally relevant animal model, we raised four Yucatan minipigs from weaning on hard diet (HD) and another four on softened but equivalent diet (SD). The animals were monitored for eight months, sacrificed, and then occlusal and osteometric data collected. Variations due to dietary regime are pervasive and not due to caries, periodontitis, or attrition differences. Whereas HD body weight is 10% greater than SD, the deep masseter is 25% greater, with similar disproportion in superficial masseter and temporalis weight. Facial prognathism, arch narrowness, tooth crowding/maleruption and posterior cranial tapering are markedly different in the two groups. A curious posterior torsional difference in the mandibular rami, as well as broadness and flatness of the mandibular symphysis, also occur in SD. We performed a Q-mode principal coordinates analysis of the 19 logged variables for the specimens, bootstrapping the variable list, to demonstrate a statistically significant (P < .01) overall pattern of dramatic differences. Having controlled other celebrated orthodontic etiologies (genetic background, respiratory mode, infectious degeneration and interproximal attrition), these results support the proposition that dietary consistency relates directly to human craniofacial growth.

Opal phytoliths found on the teeth of the extinct ape Gigantopithecus blacki: implications for paleodietary studies.

Identification of opal phytoliths bonded to the enamel surface of the teeth of Gigantopithecus blacki indicates that this extinct ape had a varied diet of grasses and fruits. By using the scanning electron microscope at magnifications of 2000-6000x specific opal phytoliths were observed and photographed on the fossilized teeth of an extinct species. Since opal phytoliths represent the inorganic remains of once-living plant cells, their documentation on the teeth of Gigantopithecus introduces a promising technique for the determination of diet in extinct mammalian species which should find numerous applications in the field of paleoanthropology as well as vertebrate paleontology.

Anthropoid origins in Asia? New discovery of amphipithecus from the eocene of burma.

A new fossil of the primate Amphipithecus mogaungensis Colbert from the late Eocene of Burma shows that this species has a mandibular and molar morphology very similar to Oligocene and post-Oligocene higher primates. It has an exceptionally deep jaw. Its brachybunodont first and second molars have smooth enamel but lack hypoconulids. The shape of its second molar is nearly square-an advanced higher primate feature. Amphipithecus mogaungensis and related taxon Pondaungia cotteri Pilgrim are the earliest known higher primates. They suggest that Southeast Asia was an early theater of higher primate diversification.

Late Eocene of Burma yields earliest anthropoid primate, Pondaungia cotteri.

In April 1978, a fragment of a primate lower jaw containing the second and third molar teeth was found in late Eocene exposures of the Pondaung Hills about 1 mile north-west of Mogaung village in northwestern Central Burma. This approximately 40-Myr-old specimen is the first fossil primate found in Burma since the fragmentary remains of the controversial earliest anthropoids Pondaungia cotteri Pilgrim and Amphipithecus mogaungensis Colbert were recovered more than 50 yr ago. The jaw described here is believed to represent further evidence of P. cotteri. Its recovery from undoubled late Eocene exposures coupled with its salient higher primate characters and excellent state of preservation provides the opportunity to substantiate further that the Pondaung primates of Burma are the earliest known record of the Anthropoidea.

Primate facial allometry and interpretations of australopithecine variation.

Pilbeam and Gould have discussed African Plio-Pleistocene hominid evolution in the context of allometry (size-dependent morphological change). These authors demonstrate that some general aspects of australopithecine morphology (tooth, brain and body size) support the hypothesis that certain early African hominids were merely scaled variations of each other at different sizes. They also speculate that the methods applied to these very broad anatomical categories can be extended to more specific and detailed traits, especially in the face and cranium. Such traits underlie most taxonomic and phylogenetic discussions of the early African Hominidae, so it is useful to follow Pilbeam and Gould's lead, as we do here, and investigate the structural differences in the australopithecine face and cranimum in a quantificiable fashion.

Morphoclinal variation in the anthropoid shoulder.

A morphocline in the organization of the shoulder joint is demonstrated among anthropoid primates. This metrical test supports the view that hominoid distinctions are monophyletic in origin. The primates that are behaviorally and functionally convergent on hominoids are only partially convergent or are not convergent in shoulder morphology.

The coraco-acromial ligament and projection index in man and other anthropoid primates.

The coraco-acromial ligament in man is a trait shared only with other hominoids (apes) among anthropoid primates. The associated form of the coracoid process and acromion, their lateral projections and the shape of the glenoid cavity likewise distinguish the Hominoidea. These anatomical features add credence to the view that the living hominoids share an independent ancestry within the Anthropoidea associated with the development of several unique locomotor/feeding adaptations.

Morphometric affinities of the human shoulder.

To analyze differences between apes and monkeys and the affinities of man, we have studied the shoulder girdle of 327 specimens of anthropoid primates. The scapula, clavicle and humerus are viewed as an integrated functional complex on the basis of 18 measurements. Several varieties of multivariate analysis show that man is clearly closer to other hominoids than to the included monkey taxa (whether terrestrial or arboreal, Old World or New World). The marked shoulder differences between apes and monkeys and similarities between apes and man correlate with the muscular anatomy, which in hominoids allows the motions involved in their locomotion and feeding behavior. As the hominid-pongid correspondence in shoulder morphology is especially detailed regarding the functionally important joint surfaces, it is consistent with a fairly recent period of common ancestry and behavior. No hypothetical evolutionary pathway or ancestral form of the human shoulder need look far beyond the model afforded by extant pongids. In contrast with previous studies on the primate shoulder, these results agree with information accumulationg from other systems--comparative anatomy, primate behavior, and molecular biology-- in suggesting very close relationship between man and extant African pongids.

Osteometric shape relationships in the wrist joint of some anthropoids.

Multivariate morphometric analyses of the wrist morphology of monkeys, apes and humans indicated that there is a fundamental difference between cercopithecoids and hominoids which can be related to functional and behavioral differences. The wrists of the Miocene fossil hominoids (Dryopithecus africanus and Pliopithecus vindobonensis) are almost completely monkey-like in their structure.