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An early depiction of Claosaurus (Wikimedia Commons)


Claosaurus (Greek for "broken lizard"); pronounced CLAY-oh-SORE-us


Woodlands of North America

Historical Period:

Late Cretaceous (80-70 million years ago)

Size and Weight:

About 15 feet long and 1,000 pounds



Distinguishing Characteristics:

Relatively small size; long tail


About Claosaurus:

For a dinosaur that was discovered so early in the history of paleontology--in 1872, by the famous fossil hunter Othniel C. Marsh--Claosaurus has remained a bit obscure. Originally, Marsh thought he was dealing with a species of Hadrosaurus, the genus that gave its name to the hadrosaurs, or duck-billed dinosaurs; he then assigned his discovery the name Claosaurus ("broken lizard"), to which he later assigned a second species, which turned out to be a specimen of yet another duck-billed dinosaur, Edmontosaurus. Confused yet?

Nomenclature issues aside, Claosaurus is important for having been an unusually "basal" hadrosaur. This dinosaur was relatively small, "only" about 15 feet long and half a ton, and it probably lacked the distinctive crest of later, more ornate hadrosaurs (we can't know for sure, since no one has found a Claosaurus skull). The teeth of Claosaurus were similar to those of a much earlier ornithopod of the Jurassic period, Camptosaurus, and its longer-than-usual tail and unique foot structure also place it on one of the earlier branches of the hadrosaur family tree.


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