SCIENCE FILE : Science in Brief : Researchers Find Jawbone of Mammal That Lived During the Dinosaur Era

UC Santa Barbara researchers have discovered a lower jawbone containing three tiny teeth from a house mouse-size mammal that lived on the island of Madagascar about 165 million years ago--while dinosaurs dominated the planet. The finding contradicts the widely held idea that mammals did not begin to develop until the dinosaurs became extinct. The finding of such early specimens from the Southern Hemisphere also contradicts the idea that mammals developed first in the north, the researchers said.

The three molars are each about the size of the head of a pin, geologist Andre R. Wyss and his colleagues report in today’s Nature. They are so small that the team did not realize they had them until they were back in the lab looking at samples.

Compiled by Times medical writer Thomas H. Maugh II