FOSSIL OF HISTORY'S MOST SUCCESSFUL MAMMAL FOUND...!

The 160 million-year-old fossil of an extinct rodent-like creature from China is helping to explain how multituberculates -- the most evolutionarily successful and long-lived mammalian lineage in the fossil record -- achieved their dominance.

This fossil find -- the oldest ancestor in the multituberculate family tree -- represents a newly discovered species known as Rugosodon eurasiaticus. The nearly complete skeleton provides critical insights into the traits that helped such multituberculates thrive in their day. For example, the fossil reveals teeth that were adapted to gnawing plants and animals alike, as well as ankle joints that were highly adept at rotation.

WHAT IS SIGNIFICANCE.?

Chong-Xi Yuan from the Chinese Academy of Geological Sciences in Beijing, China, along with Chinese and American colleagues, report their analysis of the fossil in the 16 August issue of Science.In light of these findings, researchers suggest that R. eurasiaticus paved the way for later plant-eating and tree-dwelling mammals.

The multituberculates flourished during the Cretaceous era, which ended over 60 million years ago. Much like today's rodents, they filled an extremely wide variety of niches -- below the ground, on the ground and in the trees -- and this new fossil, which resembles a small rat or a chipmunk, possessed many of the adaptations that subsequent species came to rely upon, the researchers say.

MINUTE DETAILS..!

The fossil of Rugosodon eurasiaticus is preserved in two shale slabs in part (left) and counterpart (right). It is about 17 cm (6.5 inches) long from head to rump, and is estimated to have weighed 80 grams (about 2.8 ounces). The sediments at the site of discovery are lake sediments with embedded volcanic layers. The fossil assemblage of Rugosodon also includes feathered dinosaur Anchiornis and the pterosaur Darwinopterus. By the dental features, Rugosodon eurasiaticus closely resembles the teeth of some multituberculate mammals of the Late Jurassic of the Western Europe, suggesting that Europe and Asia had extensive mammal faunal inter-changes in the Jurassic. (Credit: [Photographed by Zhe-Xi Luo of University of Chicago and Chongxi Yuan of Chinese Academy of Geological Sciences])

CONCLUSION.!

The discovery of R. eurasiaticus also extends the distribution of certain multituberculates from Europe to Asia during the Late Jurassic period, the researchers say.

"This new fossil from eastern China is very similar to the Late Jurassic fossil teeth of multituberculates from Portugal in western Europe," explained Dr. Luo. "This suggests thatRugosodon and its closely related multituberculates had a broad paleogreographic distribution and dispersals back-and-forth across the entire Eurasian continent."

The report by Yuan et al. was supported by the Ministry of Land Resources and the Ministry of Science and technology of China; the Scientific Commission of Beijing; the Beijing Museum of Natural History; the National Science Foundation; Carnegie Museum; and the University of Chicago.

SHAILESH KR SHUKLA

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