Carnegie Museum of Natural History Above: The newly discovered Chinese Cretaceous nocturnal mammal Yanoconodon was about the size of a chipmunk. It is estimated to have weighed less than one ounce and was about 5 inches long. Below: An artist's rendering of the reconstructed skeleton. Click photos for larger image.

An international team of paleontologists that included a Carnegie Museum of Natural History scientist has discovered a new species of mammal that lived 125 million years ago.

The museum today announced the discovery, made in Hebei Province in China.

The new mammal provides evidence of early evolution of mammalian middle ear -- one of the most important features for all modern mammals, according to a news release.

Named Yanoconodon after the Yan Mountains in Hebei, the fossil was unearthed in the fossil-rich beds of the Yixian Formation.

The researchers discovered that the skull of Yanoconodon revealed a middle ear structure that is somewhere 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 Dr. Zhe-Xi Luo, curator of vertebrate paleontology at Carnegie Museum.

	Carnegie Museum of Natural History A map showing where the Yanoconodon was discovered. Click photo for larger image.

Mammals have highly sensitive hearing, far better than the hearing capacity of all other vertebrates, and hearing is fundamental to mammalian way of life, the press release said. Consequently, paleontologists and evolutionary biologists have been searching for more than a century for clues on the evolutionary origins of mammal ear structure.

A report on the discovery appears in tomorrow's edition of the journal Nature.

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More details in tomorrow's Pittsburgh Post-Gazette.