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science, health & technologyAlso in this
section: Reconstructing the extinct "sea dragon" dinosaurs by Eric Jackson When the hordes of naive tourists flock to Inverness, Scotland every summer, they're looking for something that would look very much like a 19th century depiction of a plesiousaur --- a long-necked marine dinosaur that thrived in the Jurassic Age. A naive depiction, Cambridge paleontologist Leslie Noè argued in a January 3 lecture at the Smithsonian Tropical Research Institute's Tupper Auditorium. "There was a huge amount of life in the seas" during the Jurassic Age, Noè noted, including the crustaceans that appeared much earlier, many types of fish, various marine dinsosaurs and flying creatures, some in a transition that could make it hard to say whether they were dinosaurs or birds, that played roles similar to today's sea birds. This scientist has concentrated on studying the plesiosaurs --- long-necked dinosaurs with fins that indicated that they spent their entire lives in the water --- and the shorter-necked and often larger related pliosaurs. In the early 19th century when fossils of these creatures were found in the Oxford Clay Formation from which the material for the bricks that make up much of London was and still is extracted, they were described as "sea dragons" and it caught the public imagination. But although the clay around Oxford contains five or six genera of pliosaurs, Noè said that's not a lot compared to certain sites in North America, and now new finds in Colombia have attracted the attention of people in his field. His lecture in Panama was a sidelight to some field work he and colleagues will be doing in South America. The fossils recovered in the UK have been known for a century or more, and are the subjects of museum displays. But were the animals displayed right? "I may be looking at dry bones," the paleontologist said, "but I want to understand them as living creatures." That mean, for example, looking at the vertebrae of the neck, to determine what sort of range of motion the creatures had. It means looking at the teeth with a view to figuring out the sorts of things they probably ate. When he does those things, he doubts the 19th century drawings, upon which the fanciful ideas of the Loch Ness monster are based, that show a reptilian with a long neck sticking out of the water and often curving something like a swan's neck does. Plesiosaur vertebrae indicate that the creatures had little lateral movement in the necks. The mostly had up and down motion, but would not have been very efficient swimmers in the event that one of the many large predators with which they shared the same waters came around unless there was a tendon running along the neck that would have kept the head and neck straight ahead on the horizontal plane in the normal posture. Would an animal with four fully developed, hydrofoil-shaped fins swim along the top of the water with its neck stuck way up, looking around from above for things to eat? Plesiosaur teeth, Noè thinks, make that unlikely. He believes that these dinosaurs' teeth were designed for filitering crustaceans out of the sediments of shallow seas. He believes that the long necks allowed them to rummage through the muck while creating relatively little of the silt clouds that could attract predators. Thus the Nessies of old were probably grazers rather than fearsome flesh-eating dragons, and surfaced not to do swan poses for tourists but just enough to put the nostrils atop their head into the air to get a breath before resuming their bottom feeding. Also in this
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