Dryosaurus

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

• North America (Colorado, Utah, Wyoming)

• Dryosaurus altus ( Marsh, 1878)

Dryosaurus is a genus ornithopoder dinosaur from the Upper Jurassic of North America. It is one of the Dryosauridae, a group of small to medium-sized, bipedal running herbivores. All findings are from the Morrison Formation, a major fossil site in western North America. The only currently recognized species of this genus is Dryosaurus altus, though her earlier, two additional species from England and Tanzania were attributed. These species are now attributed to their own genera: Dysalotosaurus and Valdosaurus.

Features

Dryosaurus showed a typical Dryosauriden physique. Thus, the hind legs were long, the shinbone ( tibia) was longer than the thigh bone ( femur). The arms were short and ended in five fingers. The sacrum consisted of six fused sacral vertebrae, while pre-and Postpubis (the front and the back of the pubic bone ) were long and slender. The premaxillary bone ( premaxilla ), one sitting in front of the upper jaw bone was toothless, as opposed to representatives of Hypsilophodontidae. The pine ended in a beak made ​​of horn.

Paleobiology

A knochenhistologische study of John Horner and colleagues examined the growth pattern of Dryosaurus and two other ornithopods. All examined by these researchers Dryosaurus bone belonged to animals that were still in the growth - adult animals could not be traced. Maybe Dryosaurus could have completed the growth until aged 15 years. In the smaller ornithopods Orodromeus growth already in the period of youth was, however, to very hard; these animals were probably fully grown with 4 to 6 years.

Based on the remains found the relatively young animals were estimated at a length of 2.5 to 4.3 m and weighing 77-90 kilograms, and Remains of adult animals have not yet been discovered.

System

Dryosaurus is the eponymous representative of Dryosauridae, a group of Iguanodontia. The phylogenetic relationships of Dryosaurus to other Dryosauriden are unclear.

It has long been Dryosaurus as a representative of the Hypsilophodontidae. Only in 1984 was put forward by Milner and Norman the group Dryosauridae to respect the differences of Dryosaurus to Hypsilophodontidae account. In 1985, Cooper to the now discarded subfamily Dryosaurinae, which, however, he still filed within the Hypsilophodontidae.

History of discovery, discoveries and naming

The first discovery consists of a tooth, the pelvis and a hind leg ( holotype, specimen number YPM 1876) and comes from Como Bluff, Wyoming, a famous dinosaur graveyard of the Morrison Formation. Othniel Charles Marsh (1878 ) described this Fund originally as a new species of the genus Laosaurus - as Laosaurus altus. Only with the discovery of additional fossils recognized Marsh important differences between this species and other Laosaurus species, such as the longer neck vertebrae and the thinner Präpubis, and put the separate genus Dryosaurus on ( Marsh, 1894). The name Dryosaurus (Greek drys - "tree", sauros - " lizard" ) means something like " tree lizard" and probably refers to the herbivorous diet as well as on the possible waldbewohnende life of this animal. Marsh interpreted the depositional environment of the Morrison Formation - the habitat of Dryosaurus - as a lush forest with fresh water lakes.

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