Wednesday 23 May 2012

Three new species of Tapir from the Early Eocene of Pakistan.

Tapirs are large tropical, forest dwelling, herbivorous mammals related to Horses and Rhinoceroses. They have an unusual distribution, being found in South and Central America, as well as in Southeast Asia. The oldest known Tapirs in the fossil record lived in North America during the early Eocene, around 55.4 million years ago. These early Tapirs are thought to have been essentially similar to modern Tapirs, though they probably lacked the small fleshy trunk that Tapirs have today. 

Skeleton of Heptodon, the oldest known Tapir, on display in the Harvard Museum of Natural History. Flo Bruehl/Geologic Resources.

In a paper published in the journal Acta Palaeontologica Polonica on 3 March 2012, Pieter Missiaen of the Department of Paleontology at the Royal Belgian Institute of Natural Sciences and Philip Gingerich of the Museum of Paleontology at the University of Michigan describe three new species of Tapirs from the Early Eocene Ghazij Formation of Pakistan. The fossils come from Ypresian deposits in the Gandhera Quarry in Balochistan, making them between 55.8 and 48.6 million years old. All are described from their teeth and jaws only.

Map showing the locations of Eocine deposits in Pakistan and neighboring areas of India. Missiaen & Gingerich (2012).

Two of the species are assigned to the new genus Gandheralophus, implying Tapir from Gandhera. These are named Gandheralophus minor and Gandheralophus robustus (small and solid respectively). G. robustus is roughly 15% larger than G. minor, but Missiaen & Gingerich consider them to be separate species rather than two sexes of the same species as both species show bi-modal distributions of tooth size; that is to say the teeth of each species fall into two groups based upon size within the group. 

Upper dentition of Gandheralophus minor (A-F) and G. robustus (G-K). Missiaen & Gingerich (2012).

Lower dentition of Gandheralophus minor (A-D) and G. robustus (E-I). Missiaen & Gingerich (2012).

The third new species is placed in the genus Litolophus, previously described from fossils discovered in Inner Mongolia. This is named Litolophus ghazijensis, for the Ghazij Formation. In addition a number of fragments from a fourth species were discovered, though this was not named.

Teeth from the unnamed Tapir from Gandhera (A & B), and Litolophus ghazijensis (C). Missiaen & Gingerich (2012).

All of these new finds show similarities to previously discovered fossils from East and Southeast Asia. This is interesting as fossils from other mammal groups previously studied from Gandhera and neighboring areas have shown closer affinities to European faunas.

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