Earliest Remains of Jurassic Rat Relative Found in Chinese Hillside

Aug. 20, 2013— -- What comes to mind when you hear the phrase "Jurassic Park"? Chances are it's images of a gigantic Tyrannosaurus rex or velociraptors. But a newly discovered fossil found in China might make you think twice about the types of animals you would expect to find in a Jurassic-themed animal reserve.

Zhe-Xi Luo, a professor of organismal biology and anatomy at the University of Chicago, recently discovered an 160-million-year-old skeleton in the Tiaojishan Formation, about 180 kilometers, or about 112 miles, northeast of Beijing. The fossil is a near-perfect preservation of the mammal Rugosodon eurasiaticus, a rodent-like creature similar to today's African dormouse, though bigger and less cuddly.

This fossil belongs to the multituberculate order of mammals. Greg Wilson, an assistant professor of biology who specializes in early mammal history, says that these animals were incredibly successful at living and reproducing alongside dinosaurs during the Jurassic period. "Other mammals were cowering in [the dinosaurs'] shadows, but the multituberculates were unfazed," he told ABC News.

The specimen that Luo studied, which currently resides at the Beijing Museum of Natural History, was the oldest multituberculate skeleton found. "Most of these types of fossils date back from 55 [million] to 100 million years ago," said Luo.

One of the reasons that may explain some of the multituberculate's success is its multipurpose limbs. "The ankles, finger bones and the first big toe are all capable of a wide range of motion," said Luo. "This lets them do all sorts of things, like climb trees and dig tunnels."

In addition to their flexible legs and hands are the mammals' teeth. "The teeth have a lot of creases and grooves, which lets them feed on seeds and fruits but also on insects and worms," said Luo. "The teeth are very interesting and very cute."

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By having both a wide range of ways to get around and a wide range of things to eat, the multituberculates could adapt to whatever environment they were living in. "They had an incredibly long history," said Luo. "They lived with dinosaurs for 100 million years, and outlived them too."

Luo's recent research, published in last week's issue of Science, focused on the teeth and ankle bones.

"The analysis of the ankle was quite thorough," said Wilson. "But other aspects of the limbs and claws would tell us more about how it moved around in its environment. Some of us [researchers] are waiting for a more detailed analysis."

One thing that they won't need to wait for is verification of the skeleton's authenticity. Though there's been accusations in the past few years that Chinese fossils have been faked and tampered with, Luo reassures that this skeleton is the real deal.

"We put in a complete statement of authentication [with our paper]," he said. "I have my professional reputation at stake, and weeding out the fake fossils is the very first thing real professionals do."