Heritage College researcher helps unravel Madagascar’s evolutionary history

Aug 21, 2018

Analysis of teeth has led researchers to conclude that a fossil long classified as a fruit bat is actually a primate.

Nancy Stevens, Ph.D., faculty member with the Ohio University Heritage College of Osteopathic Medicine and the Ohio University Center for Ecology and Evolutionary Studies, is among the authors of a new research paper that may prompt scientists to change their long-held views on the evolutionary history of the island of Madagascar.

The paper, titled “Fossil lemurs from Egypt and Kenya suggest an African origin for Madagascar’s aye-aye,” published Aug. 21 in the online journal Nature Communications. The new study offers evidence that two lineages of lemur independently crossed the Mozambique Channel to Madagascar at different times.

The team analysed teeth from an enigmatic fossil from Kenya,  Propotto leakeyi, a bizarre and long-overlooked fossil bearing procumbent incisors and no canine teeth at all. This taxon was originally described in 1967 as a primate, but another researcher quickly challenged that view, suggesting it was a fruit bat. For decades, the taxon was of uncertain phylogenetic affinities.

Through comparisons with Plesiopithecus teras, a fossil primate from what is now Egypt that hails from around 34 million years ago, the team contends that structural similarities between the Plesiopithecus and Propotto indicate the latter is not only a primate, but a close relative of  Plesiopithecus as well as of today’s aye-aye. They postulate that a common ancestor of two different lemur lineages originated in Africa, and that the two lines dispersed from Africa to Madagascar independently.

Although additional testing of this hypothesis awaits further discovery of relevant fossils, these findings “add to the evidence that equatorial Africa likely had a key role” as a relatively temperate home for primate communities in the mid-Cenozoic era, during a time of ecological restructuring.

“The origin of lemurs has long been a topic of fascination in the scientific community,” Stevens said. “Connecting enigmatic fossils from Egypt and Kenya with the modern aye-aye helps to reveal greater complexity in the arrival of Madagascar’s fauna than previously appreciated. Remarkable discoveries await in the deepest forests, the most remote deserts and in corners of museum cabinets the world around.”

The research and its implications have attracted some international media attention, including this story from BBC News.

Stevens, a professor of functional morphology and vertebrate paleontology in the Heritage College Department of Biomedical Sciences, co-authored the paper with colleagues from Keck School of Medicine at the University of Southern California; Duke Lemur Center; the University of California – Los Angeles; Stony Brook University; the National Museums of Kenya; Wake Forest University; Mansoura University in Egypt; the American Museum of Natural History; and the Natural History Museum of Los Angeles County.