Fossils of early salamanders found. (Paleontology).

Newly discovered fossilized salamanders push back a milestone in amphibian evolution by more than 100 million years, paleontologists say.

Volcanic ash smothered members of at least five previously unknown species of cryptobranchid salamanders about 160 million years ago in what's now Inner Mongolia. Living relatives include the Asian giant salamander, which can grow as big as a small human adult, and the smaller hellbender of North America, says Neil H. Shubin of the University of Chicago.

The fine ash preserved many of the doomed creatures' soft tissues, including eye lenses, external gills, and tadpole-like tails. Even remnants of last meals were preserved, such as the bellyful of shrimp fossilized inside one 8-centimeter-long larval salamander. Juvenile members of one of the ancient species grew to at least 18 cm in length, and the adults presumably grew larger. Shubin and Ke-Qin Gao of Peking University describe the find in the March 27 Nature.

Previously, scientists held that the oldest known cryptobranchids lived about 56 million years ago. The newfound fossils suggest a surprisingly early split of this salamander lineage from a closely related salamander group, which still survives, and that cryptobranchids have changed little since that time.--S.P.