Despite their uncanny resemblance to dolphins, Hurum said there was no ancestral link.
He explained, "Both are adapted from land living animals (reptiles and mammals respectively) to live in the sea where there are not a lot of (body) shapes that work. This is a very good example of parallel evolution."
At the time of their existence, the plesiosaurs and ichthyosaurs flourished in what was then a relatively warm and shallow sea that would have been situated 62 degrees north of what is now the city of Oslo.
Continental drift over the millions of years moved them to their current, chilly location that may have preserved the fossils due to the chemical composition of mud at the site.
The ancient marine reptiles did not always get along, however. One of the plesiosaurs was found with an ichthyosaur tooth embedded in one of its neck bones. This suggests the toothy dolphin-like reptile munched down on the plesiosaur and may have even killed and eaten its flesh before leaving the bones behind.
Dave Martill, a University of Portsmouth, England, paleontologist, commented that the Svalbard site is "very unusual" and the finds from there are a "bonanza."
Hurum and his team plan to return to the area for excavation work in the summer of 2007.
He said, "What we hope to find is a dinosaur in the stomach of the Monster."
