Жоғалған құйрықты динозаврлар туысы

Extinct genus of dinosaurs

Coelurus (/s//ᵻ/'/lj//ʊər//ə//s/ siLUREəs) 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.

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". From there, the story becomes more complex. Apparently, the skeleton was scattered throughout the quarry, He returned to the genus in 1888 to add C". gracilis, based on unknown remains only represented today by a single claw bone pertaining to a small theropod from the Early Cretaceous Arundel Formation of Maryland. This species is not currently accepted as representing Coelurus in reviews of the genus, but has not been given its own genus. Despite their professional animosity, Cope also assigned species to Coelurus; in 1887, he named fossils from the Late Triassic of New Mexico as C. bauri and C. longicollis. He later gave them their own genus, Coelophysis. In 1903, Henry Fairfield Osborn named a second genus of small theropod from the Morrison Formation, Ornitholestes. This genus was based on a partial skeleton from Bone Cabin Quarry, north of Como Bluff. Ornitholestes became intertwined with Coelurus in 1920, when Charles Gilmore, in his influential study of theropod dinosaurs, concluded that the two were synonyms. This was followed in the literature for decades. The two genera were not formally compared, however, nor was there a full accounting of what actually belonged to Coelurus, until John Ostrom's study in 1980. Ostrom was also able to demonstrate that this was not the case. Additionally, he showed that one of the three vertebrae Marsh had illustrated for C. fragilis was actually a composite of two vertebrae, 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. 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, and has been regarded as a dubious species outside of Coelurus in recent reviews. Additionally, two arm bones possibly belonging to this genus are known from the Cleveland Lloyd Dinosaur Quarry in Utah. with a length of about 2.4 meters (7.9 ft) and a hip height of 0.7 meters (2.3 ft).

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, Senter proposed that Coelurus and Tanycolagreus were the only coelurids and were actually tyrannosauroids, Zanno in 2010 recovered Coelurus as a basal maniraptoran. Coelurus is sometimes put into its own family, Coeluridae, although the membership of the family has not been stable. Before the use of phylogenetic analyses, Coeluridae and Coelurosauria were taxonomic wastebaskets used for small theropods that did not belong to other groups; thus, they accumulated many dubious genera. As late as the 1980s, popular books recognized over a dozen "coelurids", including such disparate forms as the noasaurid Laevisuchus and the oviraptorosaurian Microvenator, and considered them descendants of the coelophysids. A wastebasket Coeluridae lingered into the early 1990s in some sources (and appears in at least one 2006 source) but since then it has only been recognized in a much reduced form. It remains unclear whether or not this group contains any species other than Coelurus itself, and while Tanycolagreus is often included, support for this relationship has been weak in most of the studies that recovered it. Below is a cladogram placing Coelurus in Coelurosauria by Cau et al. in 2015.

The type specimen of Coelurus agilis, YPM 2010 (now considered a synonym of Coelurus fragilis) was recovered in the Brushy Basin member of the Morrison Formation, in Albany County, Wyoming. The specimen was collected by Reed in gray sandstone and brown/green claystone that were deposited during the Kimmeridgian stage of the Jurassic period, approximately 157 to 152 million years ago. Vegetation varied from river lining forests of conifers, tree ferns, and ferns, to fern savannas with rare trees. It has been a rich fossil hunting ground, holding fossils of green algae, fungi, mosses, horsetails, ferns, cycads, ginkgoes, and several families of conifers. Other fossils discovered include bivalves, snails, ray finned fishes, frogs, salamanders, turtles such as Uluops, sphenodonts, lizards, terrestrial and aquatic crocodylomorphs like Fruitachampsa, several species of pterosaur like Kepodactylus, numerous dinosaur species, and early mammals such as docodonts, multituberculates, symmetrodonts, and triconodonts. Such dinosaurs as the theropods Ceratosaurus, Allosaurus, Ornitholestes, and Torvosaurus, the sauropods Apatosaurus, Brachiosaurus, Camarasaurus, and Diplodocus, and the ornithischians Camptosaurus, Hesperosaurus, Nanosaurus, Fruitadens, Dryosaurus, and Stegosaurus are known from the Morrison. Coelurus is regarded as a small terrestrial carnivore, feeding on small prey items like insects, mammals, and lizards. It is thought to have been a fast animal, certainly faster than the similar but shorter footed Ornitholestes.