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High dental metric variation in the large hominoid sample from the late Miocene site of Lufeng, China has been interpreted in two ways: (1) there are two morphologically similar species that broadly overlap in size, and (2) there is one species that is more highly sexually dimorphic in dental size, and perhaps in body size, than any extant primate. It has been claimed that the high levels of dental metric variation falsify the single-species hypothesis, which has been viewed implicitly as corroboration of the two-species hypothesis. However, the two-species hypothesis has not been subjected to testing. Here we test the two-species hypothesis using computer simulations to attempt to reproduce the unusual pattern of intrasexual and intersexual dental metric variation observed in the Lufeng postcanine dentition. Conditions of the simulation experiments were optimized to favor the two-species hypothesis. It was found that, although the Lufeng pattern of metric variation could be reproduced by sampling two species, the likelihood of this occurrence was very low even when the conditions were optimized to the point of improbability. We conclude that the likelihood is very high that the Lufeng sample is composed of one species that is more highly sexually dimorphic in the postcanine dentition than any extent primate species. If so, then the high levels of sexual dimorphism and intraspecific dental metric variation in this species violate the central assumption of methods that employ the coefficient of variation (CV) for paleotaxonomy, namely, that neither can lie outside the ranges observed among extant species. Thus, we further conclude that the CV must be used with caution when evaluating the taxonomic composition of fossil samples and, further, that it cannot be used to falsify a single-species hypothesis in any meaningful way. Other fossil hominoid samples with high measures of dental variation may indicate that considerable sexual size dimorphism typified many Eurasian middle–late Miocene hominoids.

Remains of the hominoidSivapithecus parvadaand a diversity of mammalian taxa are preserved at locality Y311 (ca.10Ma) in the Siwalik Nagri Formation of northern Pakistan. Bovids (Bovidae, Artiodactyla) are the most abundant mammals next to tragulids (Tragulidae, Artiodactyla) at locality Y311 and provide a means for reconstructing the paleoenvironments that would have been available toSivapithecus parvada. A functional model indicates a linkage between habitat and several femoral characters among extant bovids. Based on this model, we infer that forested habitats predominated at locality Y311 but that some less densely covered areas may also have been present. Paleoenvironments in the earlier Chinji Formation appear comparable to those at locality Y311, although the presence of a continuous canopy in the former is more certain. Thus, adaptive changes in the bovid fauna from the Chinji through the Nagri Formations appear to have preceded the shift to predominantly C4 grasslands which, based on other lines of evidence, occurred locally (and possibly globally) between 8 and 6Ma. The paleoenvironments of locality Y311 and the Chinji Formation localities appear different from the paleoenvironment ofKenyapithecusat Fort Ternan in Kenya, where the presence of continuous canopy is unlikely. The Fort Ternan fauna is dominated by two genera of bovids. One of these is adapted to light cover while the other appears better adapted to heavy cover.SivapithecusandKenyapithecuslived in different ecological settings probably characterized by varying degrees of vegetative cover.

A premaxillary fragment of Sivapithecus parvada preserving the germs of the right central and lateral incisors is described. The specimen was recovered in situ during excavation at locality Y311 in the upper Nagri Formation (ca. 9·2 m.y.a.) of the Siwalik Sequence, Potwar Plateau, Pakistan. The central incisor is approximately 35% larger than the next largest Swapithecus incisor, in keeping with the very large size of S. parvada compared to other Sivapithecus species, and is exceptionally long mesiodistally in relation to its breadth. It is also morphologically distinct, having a sharply angled distal margin and a distinct lingual tubercle. However, previous descriptions of Sivapithecus upper central incisors as having a continuous lingual shelf are in some cases erroneous and ignore the morphological variation present in the sample. In several features of anterior tooth size, morphology and proportionality, S. parvada resembles Pongo more than do other species of Sivapithecus. The I¹/I² length ratio of the new specimen is 2·12, the largest size disparity reported for any fossil catarrhine, and greater than any single value in a large sample of Pongo pygmaeus. Very great size disparity between upper central and lateral incisors is widely considered to be a synapomorphy of the orang-utan lineage. We conclude, however, that descriptions of upper incisor size heteromorphy in Pongo have in general been exaggerated and have failed to recognize substantial differences in this character between Bornean and Sumatran orang-utans. We further conclude, based on examination of a variety of Miocene hominoids and other Miocene catarrhine primates, that the character of I¹/I² proportionality has little if any phylogenetic utility within Hominoidea. Copyright 1995, 1999 Academic Press

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Examination of incisor microwear in three species of Colobus revealed that the predominantly folivorous C. badius more closely resembles C. satanas, a seed predator/ folivore, than C. guereza, another predominantly folivorous species. This demonstrates that species of the same broad dietary category can have very different patterns of incisor microwear, indicative of differences in food procurement behavior and/or the physical properties of dietary items for some portion of the diet. Conversely, species of different categories can have microwear patterns that, superficially at least, are quite similar. The dissimilarity in incisor microwear between C badius and C. guereza is mirrored to a certain extent in molar microwear, although the differences are not nearly so great on the molars. The differences between C. badius and C. guereza may involve different food items in the major, folivorous portions of their diets, or they may relate to differences in the very minor fruit and bark components. The similar microwear patterns of C. badius and C. satanas demonstrate that incisor microwear by itself is unreliable for assigning fossil species to broad dietary categories. Incisor microwear can be used to infer finer dietary distinctions in fossil species for which dietary category has been determined by other means.

The relationship between long‐sequence climate change and Miocene hominoid evolution in the Yunnan region of southwestern China has recently received some attention, partly because this region has been regarded as a “refugium” for hominoids at the end of the Miocene. Here, we carry out a high‐resolution reconstruction of climate evolution in the Zhaotong Basin of Yunnan through the late Miocene to Pliocene using chemical weathering indices and other proxies. The results reveal gradual cooling within generally warm and humid conditions from 8.8–6.2 Ma; three more marked cooling episodes from 6.2–5.0 Ma; cool and humid conditions from 5.0–2.8 Ma; finally, cold and humid conditions from 2.8–2.62 Ma. The evidence is compatible with a scenario in which terminal Miocene cooling episodes within a prevailing warm and humid climate, and associated changes in vegetation, may have been critical factors in the disappearance of hominoids from this region. Orangutans are the only Asian great apes living today, the sole remnants of a far more important radiation that occurred during the Miocene, when several species of apes are recorded from Asia, from Turkey into Pakistan, and India, and China. The Yunnan region of southwestern China has long been regarded as a “refugium” for late Miocene hominoids, as most species became extinct in Africa, Europe, and South Asia. But what caused Miocene hominoids to disappear in the Yunnan region at the southeastern margin of the Tibetan Plateau? We reconstructed a high‐resolution climate records from sediment chemical weathering, and our results suggest that warm and humid climate conditions prevailed during the known period of hominoid occupation in the region, but episodes of climate cooling at 6.2 Ma may have disrupted “refugium” and resulted in the disappearance of hominoids from the region. Generally warm and humid climate conditions during the late Miocene in southwest China provide a “refugium” for hominoids in this regionThere were four stages of climate change during the late Miocene through Pliocene in the region, including four episodes of cooler climateThe terminal Miocene cooling episodes may have been factors in the disappearance of hominoids from this region