DENVER — Talk about a creature feature: A bizarre boomerang-headed amphibian that burrowed in a seasonal pond in what is now Texas often met its doom in the jaws of a reptilian fin-backed mammalian ...

Dimetrodon borealis fossil shows a close up of a tooth with serrations (tiny bumps along the edges of the teeth). Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases ...

Dimetrodon borealis fossil with CT scan image shows teeth with long roots (in blue) and a close-up of the tooth serrations (tiny bumps along the edges of the teeth). Disclaimer: AAAS and EurekAlert!

HOUSTON They sat on the surface, next to pieces of clay and caliche rock, when paleontologists and volunteers began chiseling, scratching and brushing their way, millimeter by millimeter, toward the ...