As you may have noticed, I’m a big fan of stories about extinct animals, and the University of Alberta can usually be relied on to crank them out at regular intervals. Last week, a paper in the Journal of Vertebrate Paleontology proposed a major re-organization of the mosasaurs, sometimes called the “T-rex of the sea.”
Mosasaurs essentially looked like giant, sea-going crocodiles, with flippers for limbs and a big fluked whale-like tail. They were not dinosaurs; rather they were the biggest members ever of the order Squamata, which today includes all snakes and lizards. And I mean big; mosasaurs routinely reached sizes of 15 metres or longer. They lived in shallow seas off the continental shelves and ate whatever they could get; fish, octopus, and perhaps even shellfish. Some believe that they were so well adapted they gave birth to live young in the water. Mosasaur fossils have been found on almost every continent, in fact there are 3000 specimens from North America alone. Sorting out the relations between these skeletons, many of which consist of only a few chipped teeth, is slow, painstaking work.
Takuya Konishi knows this. He spent five years re-examining two specimens of mosasaur, one of which had been stuffed in a drawer since 1970. Among the features he noted was an unusual placement of the breathing holes. “I noticed two ridges on the top of the skull that indicate this fossil was geologically younger than others,” says Konishi. “That means this specimen was a more evolved mosasaur and I think the ridges indicate the animal’s breathing holes were set further back on the skull than earlier species.” The same pattern can be seen in modern animals; early mosasaurs can be compared to seals and walruses, which still have nostrils close to the front of their skulls. Later ones would have been more like whales and dolphins, with blowholes getting further toward the top of the skull.
By comparing his description to other specimens that had been previously described, Konishi was able to define a totally new genus of mosasaur, Latoplatecarpus, from the Latin latus (wide or extensive) and the Greek plate (oar) and karpos (wrist). His new “wide-skulled, oar-wristed lizard” genus includes two species, L. willistoni (after Samuel Wendell Willison, an Americal paleontologist who wrote one of the the first books on mosasaurs) and L. nichollsae (after Elizabeth “Betsy” Nicholls, the late Curator of Marine Reptiles at the Royal Tyrell Museum in Drumheller, where Konishi now works.)
Re-organizations of ancient species are more common than you might think, according to Konishi’s former supervisor Michael Caldwell. “Thousands of fossils from these sea-going lizards have been found and lumped together as various species of the same animal,” said Caldwell. “But Takuya had five years for a thorough doctoral examination of the fossils and with that amount of time, it makes sense a whole new genus of the creature would turn up.” And new mosasaurs are being uncovered all the time; two more were announced just today in Manitoba.
With Canada being such a great place to both find fossils and conduct research, it’s probably only a matter of time before another new species is announced.
(Check out the University of Alberta Museum’s news release on this story, which is where I got the above quotes.)