Tuesday, 16 September 2014

Newly Discovered Squirrel-Like Creatures Suggest Mammals First Appeared In The Late Triassic

September 14, 2014

Chuck Bednar for redOrbit.com – Your Universe Online

The discovery of three new small squirrel-like species lends evidence to the notion that mammals originated at least 208 million years ago in the late Triassic Period, according to new research appearing in a recent edition of the journal Nature.

The research, which was led by scientists at the American Museum of Natural History and the Chinese Academy of Sciences, places a poorly understood group of animals that lived in the Mesozoic era in the diverse family tree of mammals, which includes egg-laying monotremes like the platypus, marsupials like the opossum, and placentals like humans and whales.

“For decades, scientists have been debating whether the extinct group, called Haramiyida, belongs within or outside of Mammalia,” said co-author Jin Meng, a curator in the museum’s Division of Paleontology. “Previously, everything we knew about these animals was based on fragmented jaws and isolated teeth.”

“But the new specimens we discovered are extremely well preserved. And based on these fossils, we now have a good idea of what these animals really looked like, which confirms that they are, indeed, mammals,” he added. “They were good climbers and probably spent more time than squirrels in trees. Their hands and feet were adapted for holding branches, but not good for running on the ground.”

Those three new species – Shenshou lui, Xianshou linglong, and Xianshou songae – were described using six nearly complete 160 million year old fossils originally discovered in China, the researchers said. They were placed in a new group known as Euharamiyida that resembled small squirrels. Meng’s team believe that they weighed between one and 10 ounces, and that they ate insects, nuts, and fruit with teeth that had raised points on the crowns.

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