|
''Prosaurolophus'' (; meaning "before ''Saurolophus''", in comparison to the later dinosaur with a similar head crest) is a genus of hadrosaurid (or duck-billed) dinosaur from the Late Cretaceous of North America. It is known from the remains of at least 25 individuals belonging to two species, including skulls and skeletons, but it remains obscure. Around , its fossils have been found in the late Campanian-age Upper Cretaceous Dinosaur Park Formation in Alberta, and the roughly contemporaneous Two Medicine Formation in Montana, dating to around 75.5-71.0 million years ago. Its most recognizable feature is a small solid crest formed by the nasal bones, sticking up in front of the eyes. The type species is ''P. maximus'', described by American paleontologist Barnum Brown of the American Museum of Natural History in 1916. A second species, ''P. blackfeetensis'', was described by Jack Horner of the Museum of the Rockies in 1992. The two species were differentiated mainly by crest size and skull proportions. ==History== Well-known paleontologist Barnum Brown recovered a duckbill skull in 1915 for the American Museum of Natural History (AMNH 5836) from the Red Deer River of Alberta, near Steveville. He described the specimen in 1916 as a new genus, ''Prosaurolophus''. Brown's choice of name comes from a comparison to the genus ''Saurolophus'', which he had described in 1912. ''Saurolophus'' had a similar but longer and more spike-like head crest. The skull had a damaged muzzle and was inadvertently reconstructed too long, but better remains were soon found that showed the true shape; one is a nearly complete skeleton and skull, described by William Parks in 1924. Twenty to twenty-five individuals are known for this species, including seven skulls with at least some of the rest of the skeleton.〔 The second species, ''P. blackfeetensis'', is based on a specimen in the Museum of the Rockies (MOR 454), which was described by another notable paleontologist, Jack Horner. This specimen, and the remains of three or four other individuals, were found in Glacier County, Montana.〔 In this case, the fossils were found in a bonebed of ''Prosaurolophus'' remains, which indicates that the animals lived together for at least some time. The bonebed is interpreted as reflecting a group of animals that congregated near a water source during a drought. Horner differentiated the two species by details of the crest. He interpreted ''P. blackfeetensis'' as having a steeper, taller face than ''P. maximus'', with the crest migrating backward toward the eyes during growth. More recent studies have regarded the differences as insufficient to support two species.〔〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Prosaurolophus」の詳細全文を読む スポンサード リンク
|