Othnielosaurus

Othnielosaurus consors

• North America ( Morrison Formation )

• O. consors ( Marsh, 1878)

Othnielosaurus is a genus of bird Beck dinosaur, known from the Upper Jurassic Morrison Formation in the western United States. The genus name honors the famous paleontologist Othniel Charles Marsh, who originally assigned the fossil to the genus Laosaurus. The genus Othnielosaurus was created to accommodate fossils that were formerly assigned to the genus Othnielia, which, however, is based only on sparse existing material. It is therefore part of a decades-long work to unravel the left by Marsh and his rival Edward Drinker Cope from the Bone Wars taxonomy. Othnielosaurus is usually classified as Hypsilophodont, a group of small herbivorous or omnivorous bipeder dinosaur whose existence is contested as a valid taxon lately by scientists in question.

Description

Othnielosaurus is known of material that covers all parts of the body, including two well-preserved skeletons. The skull, however, is only poorly ( in the older literature, a variety of names for this material is used, but most publications after 1977 use the name Othnielia rex ). Othnielosaurus was a small animal, up to two meters long and 10 kilograms. It ran on two legs and therefore had short forelimbs and long rear limbs with distinct apophyses for muscle attachments. The hands of Othnielosaurus were short and broad with short fingers. Investigations of the partially preserved skull of the holotype and the skull of the possible copy Barbara showed that the head was small. The animal had small leaf-shaped cheek teeth and premaxilla teeth with less ornamentation. How many ornithopod from the groups of Hypsilophodonten or iguanodons as Hypsilophodon, Thescelosaurus, and Talenkauen had Othnielosaurus thin plates that were on his ribs. These intercostal plates were made of cartilage.

Classification

Othnielosaurus (formerly Laosaurus, Nanosaurus, and Othnielia ) was long considered hypsilophodonter Ornithopde, unclear and ill-defined group of small herbivorous dinosaur. This view was founded in 1990 by Robert Bakker et al. questioned. In their description of the new taxon Drinker Nisti they shared Othnielia into two types (O. rex and O. consors ) and established the " Othnieliden " as a more basic variant as the Hypsilophodontiden. Recent studies suggest that the Hypsilophodontidae were paraphyletic, so that the general idea of the " Othnieliden " as basal compared to other representatives of the learned Hypsilophodontiden support, although Drinker remains controversial, because since the first description nothing new has been published about the taxon. Other basal ornithopods have been betimes associated with Othnielosaurus, especially Hexinlusaurus which at least one author as a new species of the genus Othniela (O. multidens ) was considered.

Recent studies agree with the hypothesis of Othnielosaurus as basal representatives of Hypsilophodonten to, but go further than that and the genus of the ornithopods and the larger group of Cerapoda out which includes the Ceratopsia and Pachycephalosauria.

Discovery history and taxonomy

Othniel Charles Marsh named numerous species and genera in the late 19th century, which was considered Hypsilophodonten or hypshilophodonten -like dinosaurs. These included Nanosaurus agilis (possibly), Nanosaurus rex, Laosaurus celer, Laosaurus consors, and Laosaurus gracilis. This taxonomy has been over the years more and more complicated and there were various attempts since the revision.

1877 Marsh named two species of Nanosaurus in separate publications, which on incomplete remains from the Morrison Formation in Garden Park, Colorado -based. An article describing N. agilis means of a copy of the Peabody Museum of Natural History, YPM 1913, the remains included impressions of the jaw and postcranial skeleton with parts of the ilium, femur and fibula. The other publication described with Nanosaurus rex another species, the Marsh founded on the specimen YPM 1915, which is obtained only with a complete femur. He looked both ways as small ( " large fox " ) animals and put them in the now abandoned the family Nanosauridae.

A year later, Marsh described the new genus Laosaurus on the basis of material that had been excavated by Samuel Wendell Williston in Como Bluff, Wyoming. Two species were introduced: the type species Laosaurus celer, based on eleven vertebrae (YPM 1875); and the smaller Laosaurus gracilis, the description originally based on parts of a dorsal and a caudal vertebra, and a cubit.

A third type, Laosaurus consors was described by Marsh in 1894 for the specimen YPM 1882, which consisted largely of a skeleton in anatomical association and parts of at least one other individual. The skull was only partly preserved and the fact that of the vertebrae, only the vertebral bodies were obtained, points to a not fully grown individual.

This species found until the seventies and eighties, little professional attention than Peter Galton examined many of the Hypsilophodonten in a number of publications. In 1973, he described and Jim Jensen an incomplete skeleton (BYU ESM 163) rex Nanosaurus without head, hands and tail. This specimen had been damaged prior to its description. In 1977 he stated that Nanosaurus agilis from Nanosaurus rex and the new skeleton differed and coined the term Othnielia for Nanosaurus rex. This memo from 1977, which went down a bit in an article about the transcontinental nature Dryosaurus, pointed Laosaurus consors and Laosaurus gracilis new genus, without specifying exact details, and regarded as a nomen nudum Laosaurus celer. The introduction of Drinker complicated things further.

Galton led in recent times by a re-evaluation of the Ornithischia the Morrison Formation and concluded that the femur, based rex whose Nanosaurus ( and Othniela later) had been described, would not be meaningful. He therefore ordered to the BYU - skeleton of type Laosaurus consors, which is based on strong informative material. Since the genus Laosaurus also based on very informative strong material, it was the kind Laosaurus consors its own genus, Othnielosaurus. This entails that fossils of Othniela are now classified as Othnielosaurus consors. Othnielia is not a synonym of Othnielosaurus because both are based on different copies. The fossils, which have been used to describe Othniela, the genus Othnielosaurus were attributed, so that under the older name, only the original femur of the holotype is classified. The current status of the various species is as follows: Nanosaurus agilis may be a basal ornithopod, Nanosaurus rex ( Othnielia ) is a dubious basal ornithopod, Drinker Nisti retains its own provisionally valid taxon, Laosaurus consors is the type species of Othnielosaurus, and Laosaurus celer and Laosaurus gracilis are still considered doubtful.

Paleobiology and paleoecology

Othnielosaurus was one of the smaller members of the very diverse dinosaur fauna of the Morrison Formation and appears tiny compared to the giant sauropods. The Morrison Formation is considered semi-arid ecosystem with distinct wet and dry seasons, and flat floodplains. Vegetation varied from gallery forests lining the river banks and consisted of conifers, tree ferns and ferns, and savannas with ferns and scattered trees. The Morrison Formation is extremely rich in fossils. Among other things, they found the remains of chlorophytes, fungi, mosses, horsetails, ferns, cycads, ginkgo and different families of conifers. Other finds included mussels, snails, fish from the class of ray-finned fishes, frogs, salamanders, turtles, Sphenodontia, Lacertilia, terrestrial and aquatic Crocodylomorpha several types of pterosaurs, numerous species of dinosaurs and early mammals such as Representatives of Docodonta, Multituberculata, Symmetrodonta and Triconodonta. Among the species of dinosaurs were theropods like Ceratosaurus of the ecosystem, Allosaurus, Ornitholestes, and Torvosaurus. The sauropods were represented with Apatosaurus, Brachiosaurus, Camarasaurus, and Diplodocus, while Ornithischia Camptosaurus, Dryosaurus, and Stegosaurus are also known from the Morrison Formation.

Othnielosaurus occurs in stratigraphic zones 2-5.

Usually Othnielosaurus like other Hypsilophodonten interpreted as a small, nimble herbivores, although Bakker interpreted the possibly related Nanosaurus 1986 as omnivores. However, this idea found little support in the scientific literature as to test this hypothesis a better and completely as possible preserved skull is essential.