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Categories: Dinosaurs
Prosaurolophus (meaning "before Saurolophus", in comparison to the later dinosaur with a similar head crest) was a genus of duck-billed dinosaur from the Late Cretaceous of North America. It is known from remains of at least 25 individuals belonging to two species, including skulls and skeletons, but it remains obscure. Around 9 meters long (29.5 feet), its remains have been found in the late Campanian-age Upper Cretaceous Dinosaur Park Formation of Alberta, Canada, and the roughly contemporaneous Two Medicine Formation of Montana, USA, which were deposited around 75 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 Barnum Brown in 1916. A second species, P. blackfeetensis, was described by Jack Horner in 1992. Prosaurolophus was a large-headed duckbill; the most complete described specimen has a skull around 0.9 m long (2.9 ft) on a ~8.5 m long skeleton (~28 ft).[1] It had a small, stout, triangular crest in front of the eyes, deeply excavated on the sides. Otherwise, it was an unremarkable hadrosaurine hadrosaur. The two species are differentiated by details of the crest, and in profile, P. blackfeetensis is restored with a steeper, taller face than P. maximus. In P. blackfeetensis, at least, the crest migrates backward toward the eyes during growth.[2] Because of its name, Prosaurolophus is often associated with Saurolophus. However, this is contentious; some authors have found the animals to be closely related,[3] whereas others have not.[4] It was a hadrosaurine hadrosaur, meaning it lacked a hollow crest. 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 the new genus Prosaurolophus, which he compared to the earlier-named Saurolophus, which had a similar but longer head crest.[5] The skull was damaged in the muzzle and reconstructed too long,[6] 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.[7] 20 to 25 individuals are known for this species, including 7 skulls with at least some of the rest of the skeleton.[4] The second species, P. blackfeetensis, is based on 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.[2] The skeletal remains were found in a bonebed of Prosaurolophus remains, which indicates that the animals were gregarious for at least part of the year. The bonebed is interpreted as reflecting a group of animals that congregated near a water source during a drought.[8] Although many species of hadrosaurs have been consolidated, this species was considered to be valid in the most recent review.[4] As a hadrosaurid, Prosaurolophus would have been a large bipedal/quadrupedal herbivore, eating plants with a sophisticated skull that permitted a grinding motion analogous to chewing. Its teeth were continually replacing and packed into dental batteries that contained hundreds of teeth, only a relative handful of which were in use at any time. Plant material would have been cropped by its broad beak, and held in the jaws by a cheek-like organ. Feeding would have been from the ground up to ~4 m (13 ft) above.[4] In the well-studied Dinosaur Park Formation, Prosaurolophus is only known from the upper part, which had more of a marine influence than the lower section. It was the most common hadrosaurine of this section, which lasted from about 76 to about 74 million years ago.[9] As noted, there is bonebed evidence that this genus lived in groups during at least part of the year.[8] Additionally, it had several potential methods for display in a social setting. The bony facial crest is an obvious candidate, and it may have had nasal diverticula, inflatable soft-tissue sacs housed in the deep excavations flanking the crest and elongate holes for the nostrils. Such sacs could be used for both visual and auditory signals.[10]
Contents
[edit] Description
[edit] Classification
[edit] History
[edit] Paleobiology
[edit] Social behavior
[edit] References
[edit] External links
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