Key clue to amphibian evolution found in Petrified Forest
For years, debate has raged about where a group of snakelike animals fit in the amphibian family tree.
Now, an analysis in the journal Nature of fossils from Arizona’s Petrified Forest National Park may hold the answer.
A lack of fossil remains often hinders attempts to reconstruct the family tree of caecilians —– limbless, bullet-headed, wriggly amphibians that live in soil or streambeds an eat mollusks, termites, worms, small snakes and other amphibians. They also have small, sensitive tentacles, located between their nostrils and their eyes.
At 220 million years old, the fossilized remains extracted from the Petrified Forest’s portion of the Chinle geological formation are 35 million years older than previous finds.
They show the amphibians’ ancestors lacked their telltale tentacles and retained some features of an extinct group of four-legged amphibians called dissorophoid temnospondyls.
This suggests they bridged a gap between modern caecilians and those ancient, extinct amphibians and strengthens the argument that they should be clustered with frogs and salamanders in the group Lissamphibia.