Prosaurolophus
| Prosaurolophus | ||||||||||||
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Prosaurolophus maximus in the Royal Tyrrell Museum |
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| Temporal occurrence | ||||||||||||
| Upper Cretaceous (Middle to Upper Campanium ) | ||||||||||||
| 80.6 to 72 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Prosaurolophus | ||||||||||||
| Brown , 1916 | ||||||||||||
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Prosaurolophus ("before Saurolophus ", compared to the later living dinosaur with a similar head crest) was a genus of the bird's pelvis dinosaur from the group of Hadrosauridae . The genus currently contains two valid species, of which fossils of at least 25 individuals have been found in North America. The fossils come from the Middle to Upper Campanium ( Upper Cretaceous ). The skeletons were found in the Dinosaur Park Formation in Alberta , Canada , and the roughly equally old Two Medicine Formation in Montana , USA.
features
Prosaurolophus corresponded in its anatomy to the typical hadrosaurs. He reached a body length of eight to nine meters and had a very large head, which was 0.9 meters long in a 8.5-meter specimen. As with most hadrosaurs, the front part of the head was flattened and broadened like a beak, which enabled it to bite off leaves from trees in North American forests. In the oral cavity he had thousands of small teeth, through which the plant material was crushed before it was swallowed.
As the most striking feature, Prosaurolophus had a comparatively small and triangular forehead crest on the forehead in front of the eyes, which was formed by the nasal bones and whose sides formed depressions due to their concave shape. The front legs were relatively short compared to other hadrosaurs.
The two species P. maximus and P. blackfeetensis differed mainly in the proportions of the skull and the size of the forehead crest. P. blackfeetensis had a narrower and longer face, and the forehead crest of this species moved backwards towards the eyes as it grew.
Sites and history
Fossils of Prosaurolophus are known from two sites in North America, the Dinosaur Park Formation as the uppermost layer of the Judith River Group in Alberta, Canada, and the approximately equally old Two Medicine Formation in Montana, USA. Fossil skeletal remains of at least 25 individuals and seven complete skulls are known of the type species P. maximus , while P. blackfeetensis has a partially complete skeleton with skull and several individual bones. Both find areas are characterized by a variety of skeletal finds.
The earliest fossils of the P. maximus type were described in 1916 by the American paleontologist Barnum Brown of the American Museum of Natural History . He discovered a skull near the Red Deer River near the town of Steveville in Alberta, Canada (Dinosaur Park Formation) in 1915 , which is now in the American Museum of Natural History as AMNH 5836. He described the genus as Prosaurolophus in 1916 , making reference to Saurolophus, which he also described in 1912 . Like the new species, this had a conspicuous forehead crest, which, however, was longer and larger. In 1924, William Parks described an almost complete skeleton with a skull. To date, fossils of about 25 individuals are known from Canada and the formation in Montana, some in the form of almost complete skeletons and skulls.
In 1992, the paleontologist described Jack Horner of the Museum of the Rockies with P. blackfeetensis a second type on the basis of a skeleton in the Two Medicine Formation, more precisely in Glacier County , was discovered. The material was stored in the Museum of the Rockies as MOR 454, along with the remains of three or four other specimens. The fossils were found together, so it is believed that they lived together and gathered near a watering hole during a drought.
Systematics
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Prosaurolophus got its name based on the hadrosaur Saurolophus , who had a similarly formed crest, on the assumption that it could be an ancestor of the same (pre-Saurolophus). To what extent there is actually a closer relationship between the two genera is unclear; It is accepted by some authors, while others place both types in different places in the system.
According to the current idea, Prosaurolophus is placed in the Hadrosaurinae and thus in the closer relationship of the genera Brachylophosaurus , Edmontosaurus , Gryposaurus and Maiasaura . Members of this group are distinguished by the lack of a complete forehead crest, which is present in Saurolophus .
Two valid species are described within the genus, there are no nomina dubia . The type species P. maxima was first described in 1916 by Barnum Brown from the Two Medicines Formation. In 1992, the paleontologist Jack Horner from the Museum of the Rockies described a second species, P. blackfeetensis , which differed from P. maximus mainly in the proportions of the skull and the size of the forehead crest.
Paleoecology
The Dinosaur Park Formation, in which Prosaurolophus maximus was found, is considered to be a formerly flat landscape of rivers and floodplains that has become increasingly swampy as the Western Interior Seaway transgression to the west. The climate was warmer than in today's Alberta and without frost, but at the same time more humid with dry periods. The vegetation consisted mainly of coniferous plants with an undergrowth of ferns , tree ferns and seed plants . Within this well-studied fossil deposit, remains of Prosaurolophus could only be found in the uppermost layer, which was more influenced by the sea than the lower layers. Within this layer, whose age has been dated to 76-74 million years it represents the most common hadrosaur. In addition prosaurolophus also many other skeletons were found of dinosaurs, including the Ceratopsidae Centrosaurus , Styracosaurus and Chasmosaurus that the Tyrannosauridae belonging Gorgosaurus that Ankylosauria Edmontonia and Euoplocephalus as well as a number of other hadrosaurs with Gryposaurus , Corythosaurus , Lambeosaurus and Parasaurolophus .
The Two Medicine Formation, in which P. blackfeetensis was discovered, is about the same in time and is best known for the fossil finds of dinosaur nests, eggs and juveniles of the hadrosaurs Hypacrosaurus stebingeri and Maiasaura as well as the Troodontid Troodon . In addition, skeletal remains were of tyrannosaurid Daspletosaurus , the Caenagnathiden chirostenotes , the Dromaeosauriden Bambiraptor and saurornitholestes , the ankylosaurs Edmontonia and Euoplocephalus , the Hypsilophodontiden orodromeus and the Ceratopsiden Achelousaurus , brachyceratops , Einiosaurus and Styracosaurus ovatus . The site was further from the Western Interior Seaway, it was also higher and was drier than the Dinosaur Park Formation.
Paleobiology
nutrition
Like all hadrosaurs, Prosaurolophus was a large herbivore, which, thanks to its beak-like, extended and complex skull, was able to chop up parts of plants with a movement similar to chewing . His teeth were constantly being replaced and lay in packets of several hundred teeth in the jaw, only a fraction of which were used at the same time. The plant material was torn off by plants from the ground up to a height of about four meters with its broad beak and remained in the oral cavity through cheek-like formations. Like other hadrosaurs, this species probably moved four-footed (quadruped) and two-footed (biped).
Social behavior
The fact that the fossil finds were found in bone stores with several skeletons, it is deduced that these animals lived at least partially in groups. There are further assumptions for social behavior about the cranial skeleton: The bony forehead crest could have had a function as a visual means of communication, and the existence of sac-shaped and membranous diverticula on the nasal cavity is assumed, which in addition to the optical function could also have served acoustically for communication. Additionally, it had several potential methods for display in a social setting.
literature
- David B. Weishampel , Peter Dodson , Halszka Osmólska (eds.): The Dinosauria . 1st paperback edition. University of California Press, Berkeley CA et al. a. 1992, ISBN 0-520-06726-6 .
Web links
Individual evidence
- ^ Gregory S. Paul : The Princeton Field Guide To Dinosaurs. Princeton University Press, Princeton NJ u. a. 2010, ISBN 978-0-691-13720-9 , pp. 299-300 princeton.edu .
- ↑ a b after David B. Weishampel , Peter Dodson , Halszka Osmólska (ed.): The Dinosauria . 1st paperback edition. University of California Press, Berkeley CA et al. a. 1992, ISBN 0-520-06726-6 , p. 557.
- ↑ a b c Prosaurolophus ( Memento from October 4, 2007 in the Internet Archive ), data sheet on dinoruss.org.
- ↑ Published as: Barnum Brown : A new crested trachodont dinosaur Prosaurolophus maximus. In: Bulletin of the American Museum of Natural History. Vol. 35, Article 37, 1916, ISSN 0003-0090 , pp. 701-708, hdl : 2246/2246/1328 .
- ↑ Published as: Barnum Brown: A crested dinosaur from the Edmonton Cretaceous. In: Bulletin of the American Museum of Natural History. Vol. 31, Article 14, 1912, pp. 131-136, hdl : 2246/1401 .
- ↑ Published as: William A. Parks : Dyoplosaurus acutosquameus. A new genus and species of armored dinosaur and notes on a skeleton of Prosaurolophus maximus (= University of Toronto Studies. Geological Series. No. 18, ISSN 0372-4913 ). University of Toronto - University Library, Toronto 1924.
- ↑ Published as: John R. Horner : 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. No. 2). Montana State University - Museum of the Rockies u. a., Bozeman MT et al. a. 1992, ISBN 1-56044-156-9 .
- ^ A b c Raymond R. Rogers: Taphonomy of three dinosaur bone beds in the Upper Cretaceous Two Medicine Formation of northwestern Montana; evidence for drought-related mortality. In: Palaios. Vol. 5, No. 5, 1990, ISSN 0883-1351 , pp. 394-413, doi: 10.2307 / 3514834 .
- ^ A b John R. Horner, David B. Weishampel , Catherine A. Forster: Hadrosauridae. In: David B. Weishampel, Peter Dodson , Halszka Osmólska (eds.): The Dinosauria . 2nd edition. University of California Press, Berkeley CA et al. a. 2004, ISBN 0-520-24209-2 , pp. 438-463.
- ^ David A. Eberth: The Geology. In: Philip J. Currie , Eva B. Koppelhus (Eds.): Dinosaur Provincial Park. A spectacular ancient ecosystem revealed. Indiana University Press, Bloomington IN et al. a. 2005, ISBN 0-253-34595-2 , pp. 54-82.
- ^ Dennis R. Braman, Eva B. Koppelhus: Campanian palynomorphs. In: Philip J. Currie, Eva B. Koppelhus (Eds.): Dinosaur Provincial Park. A spectacular ancient ecosystem revealed. Indiana University Press, Bloomington IN et al. a. 2005, ISBN 0-253-34595-2 , pp. 101-130.
- ↑ Michael J. Ryan, David C. Evans: Ornithischian Dinosaurs. In: Philip J. Currie, Eva B. Koppelhus (Eds.): Dinosaur Provincial Park. A Spectacular Ancient Ecosystem Revealed. Indiana University Press, Bloomington IN et al. a. 2005, ISBN 0-253-34595-2 , pp. 312-348.
- ^ A b David B. Weishampel, Paul M. Barrett , Rodolfo Coria , Jean Le Loeuff, Xing Xu , Xijin Zhao , Ashok Sahni, Elizabeth Gomani, Christopher R. Noto: Dinosaur distribution. In: David B. Weishampel, Peter Dodson, Halszka Osmólska (eds.): The Dinosauria . 2nd edition. University of California Press, Berkeley CA et al. a. 2004, ISBN 0-520-24209-2 , pp. 517-683, here pp. 517-606.
- ↑ James A. Hopson: The evolution of cranial display structure in hadrosaurian dinosaurs. In: Paleobiology. Vol. 1, No. 1, 1975, ISSN 0094-8373 , pp. 21-43.