The feeding habits of an unusual 200-million-year-old fish have been uncovered by a University of Bristol undergraduate in a groundbreaking study which has been published in Palaeontology, a leading scientific journal, this week - a rare achievement for an undergraduate student. The Jurassic fish, Dapedium, known from the Lower Lias rocks of the Dorset coast around Lyme Regis, was one of many new groups of fishes that came on the scene 200 million years ago. These included ancestors of the modern teleost fishes - the group of 30,000 species of salmon1, cod2, seahorses, and perch3 - that dominate the waters today.This distinctive4 fish was also one of a number of ancient animals first discovered by the pioneering nineteenth century fossil collector Mary Anning, and fascinated early palaeontologists such as Henry De la Beche and Louis Agassiz.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 jutting5 front teeth and masses of pebble-shaped teeth further back.In his research, Bristol undergraduate Fiann Smithwick applied6 a new lever-based mechanical model, developed to understand the jaw7 mechanics of modern fishes, to reconstruct the feeding behaviour of this extraordinary ancient fish.My work indicates that Dapedium was well adapted to crush shells, said Fiann, feeding on bivalves and other hard-shelled creatures that it could scrape from the sea floor.He examined 89 specimens8 of Dapedium in the Natural History Museum, Bristol City Museum, and the Philpot Museum in Lyme Regis, and measured the positions and lengths of the jaw bones. He calculated the positions and orientations9 of jaw muscles and varied10 these to include all possible models.Every time he ran the model, the result was the same, explained Professor Mike Benton, Fianns supervisor11. The outputs showed that Dapedium was a shell crusher. Its jaws12 moved slowly, but strongly, and so it could work on the hard shells of its prey13. Other fishes have fast-moving, but weaker jaws, and those are adapted for feeding on speedy, slippery fish prey.
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1 salmon n.鲑，大马哈鱼，橙红色的 参考例句： We saw a salmon jumping in the waterfall there.大家看见一条大马哈鱼在那边瀑布中跳跃。 Do you have any fresh salmon in at the moment目前有新鲜大马哈鱼卖吗？
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