The Anterior Dentition Of Sivapithecus-parvada, With Comments On The Phylogenetic Significance Of Incisor Heteromorphy In Hominoidea

The Anterior Dentition Of Sivapithecus-parvada, With Comments On The Phylogenetic Significance Of Incisor Heteromorphy In Hominoidea

Kelley J; Anwar M; McCollum M A; Ward S C

Journal of Human Evolution

1995

1995-06

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 Sivapithecus 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.

Anthropology; clade; dentition; east-africa; evolution; Evolutionary Biology; hominids; hominoid phylogenetics; incisors; kenya; middle miocene; miocene hominoid; orangutan; origin; pakistan; pongo; sivapithecus; specimens

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