Grazing gave elephant ancestors an edge

by Mary Caperton Morton
Friday, August 3, 2018

Replica of a reconstructed Go­mpho­the­rium steinheimense skeleton on display at the Basel Natural History Museum. Credit: Zhang Hanwen, University of Bristol.

The poor dental hygiene of some ancient elephant-like beasts has proven a boon to future scientists. In a new study, researchers used grass fragments recovered from the teeth of two extinct species of Central Asian gomphotheriids to decode the animals' feeding habits during the middle Miocene.

Scientists led by Wu Yan of the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) in Beijing, China, examined bits of mineralized plant matter known as phytoliths scraped from the teeth of specimens of Gomphotherium connexum and Gompho­therium steinheimense, which both roamed Central Asia about 17 million years ago. By comparing the grazing habits of the two species, the team sought insights into how feeding preferences and changing vegetation patterns played a role in their survival.

They reported in Scientific Reports that G. connexum likely fed on mixed types of foliage, including leaves and grasses, whereas G. steinheimense showed a strong preference for grasses, a pattern also confirmed by examinations of tooth microwear patterns and structure in the two species. The team then analyzed fossil pollen records recovered from the sediments containing the teeth and found that the animals' shared habitat was changing from woodlands into semi-arid savanna. “By adopting a much more grass-based diet, G. steinheimense was apparently responding better to this habitat change than G. connexum,” said co-author Zhang Hanwen, of the University of Bristol in England, in a statement.

A grass-based diet may have given G. steinheimense an advantage over G. connexum. G. steinheimense is thought to be ancestral to modern Asian elephants, according to the study’s authors, whereas the lineages of G. connexum and several other species of gomphotheriids went extinct in Central Asia at the end of the middle Miocene. G. Steinheimense’s “active adaption to the environment helped the species to survive by better exploiting newly abundant food sources in the form of grass,” Wu told Xinhua.

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