Named By: Othniel Charles Marsh - 1890.
Synonyms: Hadrosaurus agilis.
Classification: Chordata, Reptilia, Dinosauria, Ornithischia, Ornithopoda, Hadrosauroidea.
Species: C. agilis (type), C. affinis?
Size: Roughly about 3.5 meters long.
Known locations: USA, Kansas - Niobrara Formation, Montana - Pierre Shale Formation, South Dakota - Pierre Shale Formation, Texas - Aguja Formation.
Time period: Campanian/Maastrichtian of the Cretaceous.
Fossil representation: Partial remains of a few individuals.
named as a species of Hadrosaurus
by Othniel Charles Marsh in 1872,
Marsh later renamed this species as a distinct genus, Claosaurus
1890. A second species, C. affinis, is now
considered to be
highly dubious, not only upon the grounds that it was based upon
very fragmentary toe bones, but that this fossils have now become
lost, making further studies on this species impossible.
Claosaurus is so far notable for three reasons. First is that the genus is considered to be a hadrosauroid, the group that the more advanced hadrosaurids (i.e. Edmontosaurus, Parasaurolophus, Hypacrosaurus, etc) came from. Claosaurus however is so far the most advanced hadrosauroid known without actually being a true hadrosaurid. Second is that Claosaurus grew to a fairly small size averaging only about three and a half meters in length. Third, is that several specimens of Claosaurus have been found in marine sediments. This could either indicate that these individuals were living in coastal environments, or were swept out to sea in flood waters.
-Additional characters of the Ceratopsidae, with notice of new Cretaceous dinosaurs. - American Journal of Science 39:418-426. - Othniel Charles Marsh - 1890.
- The type of Claosaurus (?) affinis Wieland. - American Journal of Science 246: 29–30. - Joseph T. Gregory - 1948.