Coelurus

Coelurus is a genus of coelurosaurian dinosaur from the Late Jurassic period (mid-late Kimmeridgian faunal stage, 155–152 million years ago). The name means "hollow tail", referring to its hollow tail vertebrae (Greek κοῖλος, koilos = hollow + οὐρά, oura = tail). Although its name is linked to one of the main divisions of theropods (Coelurosauria), it has historically been poorly understood, and sometimes confused with its better-known contemporary Ornitholestes. Like many dinosaurs studied in the early years of paleontology, it has had a confusing taxonomic history, with several species being named and later transferred to other genera or abandoned. Only one species is currently recognized as valid: the type species, C. fragilis, described by Othniel Charles Marsh in 1879. It is known from one partial skeleton found in the Morrison Formation of Wyoming, United States. It was a small bipedal carnivore with elongate legs.

==History== thumb|Othniel Charles Marsh's illustration of Coelurus vertebrae from 1884|left|upright Coelurus was described in 1879 by Othniel Charles Marsh, an American paleontologist and naturalist known for his "Bone Wars" with Edward Drinker Cope. At the time, he only described what he interpreted as vertebrae from the back and tail, found at the same location as the type specimen of his new genus and species Camptonotus dispar (later renamed Camptosaurus because Camptonotus was already in use for a cricket). Marsh was impressed with the hollow interiors of the thin-walled vertebrae, a characteristic that gave the type species its name: Coelurus fragilis. He thought of his new genus as an "animal about as large as a wolf, and probably carnivorous". Coelurus would prove to be the first named small theropod from the Morrison Formation, although at the time Marsh was not certain that it was a dinosaur. He returned to it in 1881 and provided illustrations of some bones, along with putting it in a new order (Coeluria) and family (Coeluridae).