It is quite possible that you might never have heard of the Champsosaurs. If there is a skeleton of this crocodile-like reptile in your local museum, you might be ignoring it to look at the dinosaurs or the large mammal displays. But these little guys are a pretty interesting chapter in the world of paleontology.
Champsosaurs belong to the Order Choristodera, a group of crocodile-like reptiles that diverged (separated) from the main line of diapsid reptiles during the early Cretaceous Period. The Choristodera lived in freshwater rivers and swamps, and their fossils have been found in North America, Europe, eastern Asia, and most recently in the arctic regions.
Most of the Champsosaurs are fairly small, reaching only about 1.5 meters (about 5 feet) in length, but some specimens over three meters (about 10 feet) in length have been recently found. They had long, narrow jaws with fine, pointed teeth, and closely resemble the modern gavial of India. Despite their close resemblance, they are not closely related; their similarity is due to what biologists refer to as "convergent evolution." This means that adaptation to a certain way of life in a particular environment often leads unrelated animals to have the same general body shape, and often the same type of behaviour.
The Champsosaurs fed on fish, snails, mollusks, and turtles. Their jaws were very powerful. This has been determinied by the great width of the Champsosaur skull between their eyes, providing a large area to which the jaw muscles could be attached. They probably swam the same way that our modern crocodiles and marine iguanas do, by lateral undulations of their sinuous bodies and tails, tucking their legs tightly against their bodies for more streamlined movement.
In 1997, scientists from the University of Rochester found fossils of Champsosaurs on Axel Heiberg Island in the arctic. There is a lot of volcanic activity in this area, and the fossils were found on top of a 300 meter (1,000 feet) deposit of hardened lava called basalt. This meant that the Champsosaurs had died after the volcanic rock had been laid down. Volcanic deposits are very helpful to paleontologists and geologists, in that the rocks allow us to use radiometric dating. Thus, it was determined that these Champsosaurs had died about 92 to 86 million years ago, during the Cretaceous Period.
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