Shell-crushing Jurassic fish revealed

An undergraduate student from University of Bristol, Britain, has revealed the feeding habits of an unusual 200-million-year-old fish.

The Jurassic era fish Dapedium was one of many new groups of fishes that came on the scene 200 million years ago.

"My work indicates that Dapedium was well adapted to crush shells, feeding on bivalves and other hard-shelled creatures that it could scrape from the sea floor," said Fiann Smithwick.

Dapedium was a deep-bodied fish, shaped like a dinner plate in side view which could grow to over half a metre in length.

It had a tiny mouth with jutting front teeth and masses of pebble-shaped teeth further back.

In his research, Smithwick examined 89 specimens of Dapedium and measured the positions and lengths of the jaw bones.

He calculated the positions and orientations of jaw muscles and varied these to include all possible models.

The results showed that Dapedium was a shell crusher. Its jaws moved slowly, but strongly, and so it could work on the hard shells of its prey.

In comparisons with modern fishes, Dapedium matches closely the modern sea breams.

The study appeared in the journal Palaeontology.