An international team of American and Chinese paleontologists has discovered a new species of mammal that lived 125 million years ago during the Mesozoic Era, in what is now the Hebei Province in China.

The new mammal, documented in the March 15 issue of the journal Nature, provides first-hand evidence of early evolution of the mammalian middle ear--one of the most important features for all modern mammals. The discovery was funded by the National Science Foundation (NSF).

"This early mammalian ear from China is a rosetta-stone type of discovery which reinforces the idea that development of complex body parts can be explained by evolution, using exquisitely preserved fossils," said H. Richard Lane, program director in NSF's Division of Earth Sciences, which co-funded the discovery with NSF's Division of Environmental Biology and its Assembling the Tree of Life (AToL) program.

Named Yanoconodon allini after the Yan Mountains in Hebei, the fossil was unearthed in the fossil-rich beds of the Yixian Formation and is the first Mesozoic mammal recovered from Hebei. The fossil site is about 300 kilometers outside of Beijing.

The researchers discovered that the skull of Yanoconodon revealed a middle ear structure that is an intermediate step between those of modern mammals and those of near relatives of mammals, also known as mammaliaforms.

"This new fossil offers a rare insight in the evolutionary origin of the mammalian ear structure," said Zhe-Xi Luo, a paleontologist at the Carnegie Museum of Natural History (CMNH) in Pittsburgh, Pa. "Evolution of the ear is important for understanding the origins of key mammalian adaptations."

Mammals have highly sensitive hearing, far better than the hearing capacity of all other vertebrates, scientists have found. Consequently, paleontologists and evolutionary biologists have been searching for more than a century for clues to the evolutionary origins of mammal ear struct
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Contact: Cheryl Dybas
cdybas@nsf.gov
703-292-7734
National Science Foundation
14-Mar-2007