Dryosaurus

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Dryosaurus
Skeletal reconstruction of Dryosaurus (foreground) and Ceratosaurus (background) at the Carnegie Museum of Natural History in Pittsburgh

Skeletal reconstruction of Dryosaurus (foreground) and Ceratosaurus (background) at the Carnegie Museum of Natural History in Pittsburgh

Temporal occurrence
Upper Jurassic ( Tithonian )
152.1 to 145 million years
Locations
Systematics
Dinosaur (dinosauria)
Pelvic dinosaur (Ornithischia)
Ornithopoda
Dryosauridae
Dryosaurus
Scientific name
Dryosaurus
Marsh , 1894
Art
  • Dryosaurus altus (Marsh, 1878)
Live plastic reconstruction of Dryosaurus . There is no scientific basis for the fletching shown.

Dryosaurus is a genus of ornithopod dinosaur from the Upper Jurassic North America. It belongs to the Dryosauridae , a group of small to medium-sized, two-legged herbivores. All finds come from the Morrison Formation , an important fossil deposit in western North America. The only currently recognized species of this genus is Dryosaurus altus , although two other species from England and Tanzania werepreviouslyascribed to it. These species are now assigned to their own genera: Dysalotosaurus and Valdosaurus .

features

Dryosaurus showed a body structure typical for dryosaurids. The hind legs were long, with the shinbone (tibia) longer than the thighbone (femur). The arms were short and ended in five fingers. The sacrum (sacrum) consisted of six fused sacral vertebrae, while the pre- and postpubis (the anterior and posterior parts of the pubic bone ) were long and slender. The intermaxillary bone (premaxillary), a bone sitting in front of the upper jaw, was toothless, in contrast to representatives of the Hypsilophodontidae . The jaws ended in a horn beak.

Paleobiology

A bone histological study by John Horner and colleagues examined the growth patterns of Dryosaurus as well as two other ornithopods. All of the Dryosaurus bones examined by these researchers belonged to animals that were still growing - fully grown animals could not be located. It is possible that Dryosaurus could not have finished growing until the age of 15. In the case of the smaller ornithopod Orodromeus , on the other hand, growth declined sharply in the youth phase; these animals were believed to be fully grown by 4 to 6 years of age.

Based on the remains found, the relatively young animals were estimated to be 2.5 to 4.3 m in length and 77 to 90 kilograms in weight; Remains of adult animals have not yet been discovered.

Systematics

Dryosaurus is the eponymous representative of the Dryosauridae , a group of the Iguanodontia . The relationship between Dryosaurus and other Dryosaurids is unclear.

Dryosaurus was long considered a representative of the Hypsilophodontidae . Only 1984 of Milner and Norman, the group dryosauridae placed to the differences of Dryosaurus wear to hypsilophodont bill. 1985 Cooper established the now discarded subfamily Dryosaurinae, which he still classified within the Hypsilophodontidae.

History of discovery, finds and naming

The first find consists of a tooth, the pelvis and a hind leg ( holotype , copy number YPM 1876) and comes from Como Bluff in Wyoming , a famous dinosaur cemetery of the Morrison Formation . Othniel Charles Marsh (1878) originally described this find as a new species of the genus Laosaurus - Laosaurus altus . It was only with the discovery of further fossils that Marsh recognized important differences between this species and other Laosaurus species, such as the longer cervical vertebrae and the thinner prepubis, and established the independent genus Dryosaurus (Marsh, 1894). The name Dryosaurus ( gr. Drys - "tree", sauros - "lizard") means something like "tree lizard" and probably refers to the herbivorous diet and the possible forest-dwelling way of life of this animal. Marsh interpreted the deposition area of ​​the Morrison Formation - the habitat of Dryosaurus - as a lush forest with freshwater lakes.

A nearly complete skeleton including a crushed skull (copy number CM 3392) was recovered from the Dinosaur National Monument in Utah around 1922 and was described by Gilmore in 1925. Today this skeleton is on display at the Carnegie Museum of Natural History in Pittsburgh . Other finds come from Montrose County in Colorado, where numerous fragmentary remains of young animals were discovered (Galton and Jensen, 1973), from the Bone Cabin Quarry dinosaur cemetery in Wyoming, from the Elk Mountains in Johnson County in Wyoming, and from the Moffat County in Colorado.

Web links

Commons : Dryosaurus  - collection of images, videos and audio files

Individual evidence

  1. ^ Gregory S. Paul : The Princeton Field Guide To Dinosaurs. Princeton University Press, Princeton NJ et al. 2010, pp. 281-283, ISBN 978-0-691-13720-9 , online .
  2. ↑ Tom R. Hübner, Oliver WM Rauhut : A juvenile skull of Dysalotosaurus lettowvorbecki (Ornithischia: Iguanodontia), and implications for cranial ontogeny, phylogeny, and taxonomy in ornithopod dinosaurs. In: Zoological Journal of the Linnean Society. Vol. 160, No. 2, 2010, ISSN  0024-4082 , pp. 366-396, doi : 10.1111 / j.1096-3642.2010.00620.x .
  3. ^ A b Andrew T. McDonald, James I. Kirkland , Donald D. DeBlieux, Scott K. Madsen, Jennifer Cavin, Andrew RC Milner, Lukas Panzarin: New Basal Iguanodonts from the Cedar Mountain Formation of Utah and the Evolution of Thumb-Spiked Dinosaurs. In: PLoS ONE . Vol. 5, No. 11, 2010, e14075, doi : 10.1371 / journal.pone.0014075 .
  4. ^ Peter M. Galton : The Upper Jurassic dinosaur Dryosaurus and a Laurasia-Gondwana connection in the Upper Jurassic. In: Nature . Vol. 268, No. 5617, 1977, pp. 230-232, doi : 10.1038 / 268230a0 .
  5. ↑ a b c d Donald F. Glut: Dinosaurs. The Encyclopedia. McFarland & Co, Jefferson, NC 1997, ISBN 0-89950-917-7 .
  6. ^ John R. Horner , Armand De Ricqlès, Kevin Padian , Rodney D. Scheetz: Comparative Long Bone Histology and Growth of the "Hypsilophodontid" Dinosaurs Orodromeus makelai, Dryosaurus altus, and Tenontosaurus tillettii (Ornythlschla: Euornithopoda). In: Journal of Vertebrate Paleontology. Vol. 29, No. 3, 2009, ISSN  0272-4634 , pp. 734-747, doi : 10.1671 / 039.029.0312 .
  7. ↑ John R. Horner , de Ricqlés, Armand; Padian, Kevin; and Scheetz, Rodney D .: Comparative long bone histology and growth of the "hysilophodontid" dinosaurs Orodromeus makelai , Dryosaurus altus , and Tenontosaurus tillettii (Ornithischia: Euornithopoda) . In: Journal of Vertebrate Paleontology . 29, No. 3, 2009, pp. 734-747. doi : 10.1671 / 039.029.0312 .
  8. ↑ Ben Creisler: Dinosauria Translation and Pronunciation Guide ( Memento of October 13, 2011 in the Internet Archive )