Plesiosaur a victim of shark attack

Plesiosaurs were long-necked marine reptiles from the Jurassic period. The fossil of the approximately 7 meter (23 ft) sea creature, now called Futabasaurus suzukii, was discovered by a high school student in Japan in 1968, but it could not be properly examined until recently because of a lack of comparative samples, and a shortage of resources.

Professor Kenshu Shimada, a paleontologist from DePaul University in Chicago, said he remembered hearing of the fossil with shark teeth embedded in it when he was a child in Japan, but when he read the recently released description saying there were more than 80 teeth found either embedded in the bones or in the immediate vicinity, he wanted to take a closer look. He found that the teeth belonged to about seven sharks, which suggests it was a group event.

Shimada identified the sharks that attacked the hapless plesiosaur as juvenile and adult Cretalamna appendiculata, extinct ancestors of today's great white shark. The sharks possibly ranged in size from 1.5 to 4.25 meters (5-14 ft), which is much smaller than the plesiosaur, itself a major predator.

Professor Shimada said the sharks would have been no match for a healthy plesiosaur and its razor-sharp teeth, and the animal may have been dying or dead. Another paleontologist, Jorgen Kriwet, from the State Museum of Natural History in Stuttgart, Germany, agreed the plesiosaur was probably badly wounded. He said this kind of behavior is often seen today, with sharks attacking injured animals much larger than themselves, regularly losing some of their teeth in the process.

The findings were presented in a paper at the Society of Vertebrate Paleontology's annual meeting in Bristol, U.K., and will be published in the Journal of Vertebrate Paleontology.

More information: Related article: Kenshu Shimada, Cynthia K. Rigsby, and Sun H. Kim, Journal of Vertebrate Paleontology, 2009, 29(2):336-349, http://www.vertpaleo.org/publications/jvp/29-2/29-336-349.cfm

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