Prosaurolophus

From Wikipedia, the free encyclopedia

Prosaurolophus
Fossil range: Late Cretaceous

Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Sauropsida
Superorder: Dinosauria
Order: Ornithischia
Suborder: Ornithopoda
Infraorder: Iguanodontia
Superfamily: Hadrosauroidea
Family: Hadrosauridae
Subfamily: Hadrosaurinae
Genus: Prosaurolophus
Brown, 1916
Species
  • P. maximus Brown, 1916 (type)
  • P. blackfeetensis Horner, 1992

Prosaurolophus (pronounced /ˌproʊsɔˈrɒləfəs/, 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 9 meters long (29.5 ft), its fossils 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.

Contents

[edit] Description

Prosaurolophus was a large-headed duckbill; the most complete described specimen has a skull around 0.9 meters long (2.9 ft) on a ~8.5 meter long skeleton (~28 ft).[1] It had a small, stout, triangular crest in front of the eyes; the sides of this crest were concave, forming depressions. The upper arm was relatively short.[2] Otherwise, it s anatomy was unremarkable for a hadrosaurine hadrosaurid. 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 migrated backward toward the eyes during growth.[3]

[edit] Classification

Skull of Prosaurolophus maximus.
Skull of Prosaurolophus maximus.

Because of its name, Prosaurolophus is often associated with Saurolophus. However, this is contentious; some authors have found the animals to be closely related,[4][5] whereas others have not, instead finding it closer to Brachylophosaurus, Edmontosaurus, Gryposaurus, and Maiasaura.[6] It was a hadrosaurine hadrosaur, meaning it lacked a hollow crest.

[edit] 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 the new genus Prosaurolophus in comparison to the genus Saurolophus which he'd described in 1912. Saurolophus had a similar but longer and more spike-like head crest.[7] The skull was damaged in the muzzle and inadvertently reconstructed too long,[8] 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.[9] 20 to 25 individuals are known for this species, including seven skulls with at least some of the rest of the skeleton.[6]

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, Montana.[3] The skeletal remains 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.[10] Although many species of hadrosaurs have been consolidated, this species was considered to be valid in the most recent review.[6]

[edit] Paleoecology

The Dinosaur Park Formation, home to Prosaurolophus maximus, is interpreted as a low-relief setting of rivers and floodplains that became more swampy and influenced by marine conditions over time as the Western Interior Seaway transgressed westward.[11] The climate was warmer than present-day Alberta, without frost, but with wetter and drier seasons. Conifers were apparently the dominant canopy plants, with an understory of ferns, tree ferns, and angiosperms.[12] In this well-studied formation, P. maximus 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 was deposited from about 76 to about 74 million years ago.[13] The Dinosaur Park Formation was also home to well-known dinosaurs like the horned Centrosaurus, Styracosaurus, and Chasmosaurus, fellow duckbills Gryposaurus, Corythosaurus, Lambeosaurus, and Parasaurolophus, tyrannosaurid Gorgosaurus, and armored Edmontonia and Euoplocephalus.[14]

The roughly contemporaneous Two Medicine Formation, home to P. blackfeetensis, is well known for its fossils of dinosaur nests, eggs, and young, produced by the hadrosaurids Hypacrosaurus stebingeri and Maiasaura, and the troodontid Troodon. The tyrannosaurid Daspletosaurus, caenagnathid Chirostenotes, dromaeosaurids Bambiraptor and Saurornitholestes, armored dinosaurs Edmontonia and Euoplocephalus, hypsilophodont Orodromeus, and horned dinosaurs Achelousaurus, Brachyceratops, Einiosaurus, and Styracosaurus ovatus were also present.[14] This formation was more distant from the Western Interior Seaway, higher and drier, with a more terrestrial influence.[10]

[edit] Paleobiology

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 replaced 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 around 4 meters (13 ft) above.[6]

[edit] Social behavior

As noted, there is bonebed evidence that this genus lived in groups during at least part of the year.[10] Additionally, it had several potential methods for display in a social setting. The bony facial crest is an obvious candidate, and nasal diverticula may also have been present, 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.[15]

[edit] References

  1. ^ Lull, Richard Swann; and Wright, Nelda E. (1942). Hadrosaurian Dinosaurs of North America, Geological Society of America Special Paper 40. Geological Society of America, 226. 
  2. ^ Lull, Richard Swann; and Wright, Nelda E. (1942). Hadrosaurian Dinosaurs of North America, Geological Society of America Special Paper 40. Geological Society of America, 172-175. 
  3. ^ a b Horner, John R. (1992). "Cranial morphology of Prosaurolophus (Ornithischia: Hadrosauridae) with descriptions of two new hadrosaurid species and an evaluation of hadrosaurid phylogenetic relationships". Museum of the Rockies Occasional Paper 2: 1–119. 
  4. ^ Weishampel, David B.; and Horner, Jack R. (1990). "Hadrosauridae", in Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 1st, Berkeley: University of California Press, 534-561. ISBN 0-520-06727-4. 
  5. ^ Gates, Terry A.; Sampson, Scott D. (2007). "A new species of Gryposaurus (Dinosauria: Hadrosauridae) from the late Campanian Kaiparowits Formation, southern Utah, USA" (pdf). Zoological Journal of the Linnean Society 151 (2): 351–376. doi:10.1111/j.1096-3642.2007.00349.x. 
  6. ^ a b c d Horner, John R.; Weishampel, David B.; and Forster, Catherine A (2004). "Hadrosauridae", in Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press, 438-463. ISBN 0-520-24209-2. 
  7. ^ Brown, Barnum (1916). "A new crested trachodont dinosaur, Prosaurolophus maximus". Bulletin of the American Museum of Natural History 35 (37): 701–708. 
  8. ^ Lull, Richard Swann; and Wright, Nelda E. (1942). Hadrosaurian Dinosaurs of North America, Geological Society of America Special Paper 40. Geological Society of America, Plate 22. 
  9. ^ Parks, William A (1924). "Dyoplosaurus acutosquameus, a new genus and species of armoured dinosaur; and notes on a skeleton of Prosaurolophus maximus". University of Toronto Studies, Geological Series 18: 1–35. 
  10. ^ a b c Rogers, Raymond R. (1990). "Taphonomy of three dinosaur bone beds in the Upper Cretaceous Two Medicine Formation of northwestern Montana: Evidence for drought-related mortality". Palaios 5 (5): 394–413. doi:10.2307/3514834. 
  11. ^ Eberth, David A. 2005. "The geology", in Dinosaur Provincial Park, pp. 54–82.
  12. ^ Braman, Dennis R., and Koppelhus, Eva B. 2005. "Campanian palynomorphs", in Dinosaur Provincial Park, pp. 101–130.
  13. ^ Ryan, Michael J.; and Evans, David C. (2005). "Ornithischian Dinosaurs", Dinosaur Provincial Park: A Spectacular Ancient Ecosystem Revealed. Bloomington: Indiana University Press, 312-348. ISBN 0-253-34595-2. 
  14. ^ a b Weishampel, David B.; Barrett, Paul M.; Coria, Rodolfo A.; Le Loeuff, Jean; Xu Xing; Zhao Xijin; Sahni, Ashok; Gomani, Elizabeth, M.P.; and Noto, Christopher R. (2004). "Dinosaur Distribution", in The Dinosauria (2nd), pp. 517–606.
  15. ^ Hopson, James A. (1975). "The evolution of cranial display structures in hadrosaurian dinosaurs". Paleobiology 1 (1): 21–43. 

[edit] External links

Dinosaurs Portal