Othnielosaurus

Othnielosaurus Temporal range: Late Jurassic, 155–148 Ma PreЄ Є O S D C P T J K Pg N
Fossil, Paleontology Museum of Zurich
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Dinosauria
Order:	†Ornithischia
Clade:	†Genasauria
Clade:	†Neornithischia
Genus:	†Othnielosaurus Galton, 2007
Species:	†O. consors
Binomial name
Othnielosaurus consors (Marsh, 1878 [originally Laosaurus consors])

Othnielosaurus is a genus of ornithischian dinosaur that lived about 155 to 148 million years ago, during the Late Jurassic-age Morrison Formation of the western United States. It is named in honor of famed paleontologist Othniel Charles Marsh, and was formerly assigned to the genus Laosaurus. This genus was coined to hold fossils formerly included in Othnielia, which is based on remains that may be too sparse to hold a name; as such, it is part of decades of research to untangle the taxonomy left behind by Marsh and his rival Edward Drinker Cope from the Bone Wars. Othnielosaurus has usually been classified as a hypsilophodont, a type of generalized small bipedal herbivore or omnivore, although recent research has called this and the existence of a distinct group of hypsilophodonts into question.

Othnielosaurus is known from material from all parts of the body, including two good skeletons, although the skull is still poorly known (note that earlier references use a multitude of names for this material, with most of them since 1977 using Othnielia rex).Othnielosaurus was a small animal, 2 meters (6.6 ft) or less in length and 10 kilograms (22 lb) or less in weight. It was a bipedal dinosaur with short forelimbs and long hindlimbs with large processes for muscle attachments. The hands were short and broad with short fingers. From the partial type skull and the skull on the possible specimen "Barbara", the head was small. It had small leaf-shaped cheek teeth (triangular and with small ridges and denticles lining the front and back edges), and premaxillary teeth with less ornamentation. Like several hypsilophodont or iguanodont-grade ornithopods such as Hypsilophodon, Thescelosaurus, and Talenkauen, Othnielosaurus had thin plates lying along the ribs. Called intercostal plates, these structures were cartilaginous in origin.