C. fragilis was actually a composite of two vertebrae, one of which was later shown to come from another quarry and belonged not to Coelurus but to another, unnamed small theropod. This unnamed genus would not be the last small theropod from the Morrison Formation to be confused with Coelurus; a later discovery (1995) of a partial skeleton in Wyoming was first thought to be a new larger specimen of Coelurus, but further study showed it belonged to a different but related genus, Tanycolagreus. Species Only one species of Coelurus, the type species C. fragilis, is still recognized as valid today, although six other species have been named over the years. C. agilis, as discussed, was named by Marsh in 1884 for what turned out to be additional parts of the skeleton of C. fragilis. Cope's C. bauri and C. longicollis, named in 1887 from Late Triassic fossils from New Mexico, were transferred by Cope in 1889 to his new genus Coelophysis. C. daviesi was named by Richard Lydekker in 1888 for Harry Seeley's Thecospondylus daviesi, a neck vertebra from the Early Cretaceous of England, but this species was later transferred to its own genus, Thecocoelurus. C. gracilis, another Early Cretaceous species, was also named in 1888. It was coined by Marsh for what seems to be an assortment of limb remains, but Gilmore could only find a single claw when he reviewed the species in 1920. This species has been proposed as outside Coelurus since the 1920s (when Gilmore assigned it to Chirostenotes), and has been regarded as a dubious species outside of Coelurus in recent reviews. Finally, during the period when Ornitholestes was thought to be the same as Coelurus, its type species was recognized as distinct by Steel, as C. hermanni. Classification Since the growth of phylogenetic studies in the 1980s, Coelurus has usually been found to be a coelurosaurian of uncertain affinities, not fitting with the better-known clades of the Cretaceous. Along with several other generalized coelurosaurians such as the compsognathids, Ornitholestes, and Proceratosaurus, it has had multiple placements around the base of Coelurosauria. The phylogenetic analysis conducted by Rauhut (2003) and Smith et al. (2007) found that Coelurus was more closely related to compsognathids than to other coelurosaurs. Oliver Rauhut (2003) proposed that Coeluridae was composed of Coelurus plus the compsognathids, but he and others have not since found the compsognathids to group with Coelurus.