| Claosaurus | |
|---|---|
 | |
| Type specimen in thePeabody Museum, with restored skull[1] | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | †Ornithischia |
| Clade: | †Ornithopoda |
| Clade: | †Hadrosauromorpha |
| Genus: | †Claosaurus Marsh,1890 |
| Type species | |
| †Hadrosaurus agilis (Marsh, 1872a) Marsh, 1890 | |
| Synonyms | |
| |
Claosaurus (/ˌkleɪəˈsɔːrəs/KLAY-ə-SOR-əs;Greek κλάω,klao meaning 'broken' andσαῦρος,sauros meaning 'lizard'; "broken lizard", referring to the odd position of thefossils when discovered) is agenus ofhadrosauroiddinosaur that lived during theLate CretaceousPeriod (Santonian-Campanian).[2]
Traditionally classified as an early member of the familyHadrosauridae, a 2008 analysis foundClaosaurus agilis to be outside of theclade containingHadrosaurus and other hadrosaurids, making it the closest non-hadrosaurid relative of true hadrosaurids within the clade Hadrosauromorpha.[3]
Because of the insufficient fossil remains ("minority of skull and partial skeleton"), the size of an adultClaosaurus remains uncertain.[4] However, Thomas Holtz gave a length estimate of 3.7 m (12 ft) and a mass estimate as that of a lion.[5] Like other hadrosaurs, it was anherbivore.[3]
Evidence of its existence was first found in theNiobrara Formation near theSmoky Hill River inKansas, United States in the form of partial skull fragments and as an articulated postcranial skeleton. Originally namedHadrosaurus agilis (Marsh, 1872), it was placed in a new genus and renamedClaosaurus agilis in 1890 when major differences between the specimen andHadrosaurus came to light.[6]
In 1892, Marsh named a second species,C. annectens. It was later reassigned toAnatosaurus and thenEdmontosaurus, where it is currently.[7] G. R. Wieland named third speciesC. affinis in 1903, which he compared toC. annectens.C. affinis was founded on remains from thePierre Shale ofSouth Dakota, found in association with remains of the giant sea turtleArchelon. At some point after its description, the fragmentary remains were mixed up with the original remains ofC. agilis, and a toe bone fromC. agilis was accidentally thought to be the only part of theholotype remains that could be located. This was corrected by Joseph Gregory in 1948, who found three toe bones from the right foot of a large hadrosaur in the Yale collections that had comparable preservation to the Pierre Shale turtle remains and were associated with labels in Wieland's handwriting. Gregory found the toe bones to be very similar in size to the corresponding bones of Marsh'sClaosaurus annectens, but did not reassign the species due to its much older age and fragmentary remains.[8]C. affinis was considered adubious hadrosaur in the 2004 review by Jack Horner and colleagues. They reported its type material as lost, although they also reported the remains as only including a single toe bone, instead of the three toe bones described by Gregory.[7]
Reports ofgastroliths, or stomach stones, inClaosaurus are actually based on a probable double misidentification. The specimen thought to have gastroliths is actually ofEdmontosaurus annectens.Barnum Brown, who discovered the specimen in 1900, referred to it asClaosaurus, becauseE. annectens was thought to be a species ofClaosaurus at the time. Additionally, it is more likely that the supposed gastroliths represent gravel washed in during burial.[9]
Winter 2011 Appendix
