Australian scientists say fossilized muscle has been discovered in the remains of two fish that lived about 380 million years ago.
The fish, discovered in western Australia 20 years ago, belong to two species of an extinct group of primitive, armored fish known as placoderms, National Geographic News reported.
The remarkably well-preserved soft tissues included bundles of muscle cells, blood vessels, and nerve cells that are the oldest ever found. The tissue was discovered only recently during electron microscope scanning.
Fossilized muscle is quite rare and the discovery is even more remarkable since the remains weren't flattened, but were preserved with their three-dimensional shape intact, the researchers told NGN.
The remains shed light on the evolution of placoderms, which ruled the world's oceans, rivers, and lakes for 70 million years until they died out about 360 million years ago.
"On the evolutionary tree, they're the first jawed animal, and we're the last, lead study author Kate Trinajstic, a paleontologist at the University of Western Australia, told National Geographic News. "So they're our first jawed ancestors."
The research appears in the British journal Biology Letters.
Copyright 2007 by United Press International
Explore further: Oldest pterodactyloid species discovered, named by international team of researchers