Plesiosaurs ate snails and clams
ABC Science Online
Friday, 7 October 2005
Scientists have found a seafood feast in the fossilised stomach remains of two plesiosaurs, long-necked aquatic predators that lived at the same time as the dinosaurs.
The find suggests these animals had a much more balanced diet than once thought, which researchers say probably explains why they survived for so many millions of years.
Australian researcher Professor Stephen Wroe, of the University of Sydney, and colleagues report their findings in today’s issue of the journal Science.
Plesiosaurs are carnivorous reptiles with an unusually long neck.
Those in the elasmosaur family have the longest neck of all, at more than twice the length of the body and tail put together.
Their large number of relatively small but very sharp teeth are well suited to grasping slippery and free-swimming fish or squid.
And studies of fossilised gut contents from North American plesiosaurs suggest this is what they ate.
Scientists just presumed their long necks must have been some kind of adaptation to catching agile fish and squid, says Wroe.
But the new research has found that the plesiosaur’s long neck also allowed the animal to feed on bottom-dwelling life.
“Their diet is much more balanced that we’d imagined,” Wroe says.
Looking into the stomach
Wroe and colleagues analysed the fossilised stomach remains of two plesiosaurs that lived around 100 to 110 million years ago found recently in marine deposits in northwestern Queensland.
One stomach was full of crushed clams and snails while the other contained pieces of clam.
The researchers also found a piece of fossilised plesiosaur poo which confirms the plesiosaur had eaten the seafood, rather than the plesiosaur remains containing seafood by accident.
“[The poo] was largely made up of crushed up mollusc shell,” says Wroe.
He says the fact that plesiosaurs could eat such a diverse diet might help to explain why the animals were so successful.
“Long-necked plesiosaurs were around for at least 135 million years and that’s quite a success story,” he says.