Two Canadian scientists have helped give one of the most ferocious monsters of the dinosaur age a major makeover.
Overturning decades of conventional wisdom about the shape and swimming style of the mosasaur — a huge marine lizard known from fossil discoveries in Alberta, Saskatchewan and Manitoba — the researchers’ new study has pinned a shark-like tail on the predatory reptile that ruled the vast oceans of Cretaceous Canada.
University of Alberta scientists Michael Caldwell and Takuya Konishi, along with colleagues in Sweden and the U.S., published their findings this week in PLoS One, a journal of the U.S.-based Public Library of Science.
The researchers based their conclusions on a fresh study of the finest preserved mosasaur in existence, a sub-species known as platecarpus held by the Natural History Museum of Los Angeles County.
Their analysis of the seven-metre-long creature’s body size and bone structure led them to debunk a long-standing theory that mosasaurs had a tapered tail and moved with eel-like undulations in search of fish and other prey some 85 million years ago.
Instead, they concluded, the shape and orientation of the lizard’s back bones must have supported a crescent-shaped tail fin — unlikely to be preserved in fossil form — that gave it a powerful swimming thrust similar to that of a great white shark.
Like other groups of sea creatures that evolved to maximize their swimming speed and efficiency, the researchers state in the journal article, mosasaurs radically modified their tails, stiffened their backbones, and reduced their rear limbs to meet the demands of marine life.
If the new theory holds, showcase mosasaur reconstructions at dinosaur museums around the world — including several in Canada — may require some remodelling to add a prominent tail to the extinct beast.
“This fossil shows evolution in action, how a successful design was developed time after time by different groups of organisms adapting to life in similar environments,” co-author Luis Chiappe, director of the Los Angeles museum’s Dinosaur Institute, said in a summary of the study. “It highlights once again the potential for new discoveries to challenge well-established interpretations about dinosaurs and other animals that lived with them.”
The first fossilized mosasaur remains were discovered in 1770 in a cave in the Netherlands. Along with the numerous specimens collected from Western Canada, mosasaurs have been found in many sites around the world — a testament to the widespread success of the species for millions of years during the Cretaceous era.
Notable Canadian specimens include the famous Manitoba mosasaur nicknamed Bruce, a 13-metre-long individual dug up near the town of Thornhill in 1974 and now displayed at the Canadian Fossil Discovery Centre in Morden, Man.