The long-necked marine reptiles of the dinosaur age had a taste for shellfish, two Australian fossils reveal. Palaeontologists had thought elasmosaurs used their exceptionally long necks simply to catch fish.
Elasmosaurs evolved from marine reptiles called plesiosaurs, which first appeared more than 200 million years ago. With a small head on the end of a long neck, and flippers on its body, elasmosaurs looked so odd that an unidentified Victorian palaeontologist called one "a snake threaded through the body of a turtle".
Later researchers considered elasmosaurs highly specialised for catching free-swimming fish and squid-like animals, a belief supported by the discovery of fish bones in the bellies of North American fossils, along with stones the animals had swallowed, probably to control buoyancy and aid digestion.
Now two Australian fossils show elasmosaurs also ate slow-moving sea-floor animals. One fossilised stomach cavity contained fragments of bivalve and snail shells, while the other contained pieces of crab shell. Both stomachs also boasted the remains of squid-like animals (including shell in one case), a fish scale, as well as stomach stones that probably helped crush the shells.
The discovery "made me revise a lot of what I'd thought about these animals", says Colin McHenry at the University of Newcastle in New South Wales, who analysed the fossils with Alex Cook of the Queensland Museum and Stephen Wroe of the University of Sydney, all in Australia.
McHenry thinks the elasmosaurs reached down with their necks to graze on bottom-dwellers at depths to 30 metres, probably swallowing their prey whole. He now believes the long neck was "part of a more generalised body plan" adaptable to many environments, allowing the elasmosaurs species and related long-necked plesiosaurs to survive for 135 million years.
Journal reference: Science (vol 310, p 75)
