Coelurus ‭(‬Hollow tail‭)

Short Info

Coelurus ‭(‬Hollow tail‭)

Phonetic : See-lur-us.

Named By : Othniel Charles Marsh‭ ‬-‭ ‬1879

Diet : Carnivore

Size : Estimated 1.8-2.4 meters long

Type of Dinosaur : Small Theropod

Type Species : C.‭ ‬fragilis (type)

Found in : USA,‭ ‬Wyoming‭ ‬-‭ ‬Morrison Formation

When it Lived :
Late Jurassic, 155-145 million years ago

Coelurus (/sI’ljU@r@ssi-LURE@s) is one of the genus belonging to the coelurosaurian dinosaurs that lived in early in the Late Jurassic period (mid-late Kimmeridgian faunal stage, between 155 and 152 millions of years ago). The name refers to “hollow tail”, referring to its hollow-tailed vertebrae (Greek Koilos, koilos is hollow and oura = means tail). Though its name is tied with one of the principal categories of theropods (Coelurosauria) It was not well-known historically and often confused with its more well-known counterpart Ornitholestes. As with many dinosaurs that were studied in the beginning of paleontology, this one has experienced a complicated taxonomic background and several species were designated and then later moved to different genera or even abandoned. One species is acknowledged as legitimate: the type of species C. fragilis discovered by Othniel Charles Marshall in 1879. It was identified from a partial skeleton that was found within the Morrison Formation of Wyoming, United States. It was a tiny bipedal carnivore that had elongate legs.

Jaime A. Headden (User:Qilong), CC BY 3.0, via Wikimedia Commons

Coelurus is identified from the vast majority of the skeletons of an individual, comprising many vertebrae, a portion of shoulder and pelvic girdles and a significant portion of the legs and arms that are stored in the Peabody Museum of Natural History However, the totality of the skeleton was not discovered until the year the year 1980. The fossils were found in Reed’s Quarry 13 at Como Bluff, Wyoming. Two arm bones which could be belonging to the genus known as the Cleveland-Lloyd Dinosaur Quarry in Utah. The dinosaur was certainly not a massive dinosaur. Its weight was estimated to be between 13 and 20 kg (29 to 44 lbs) in length, with a height of around 2.4 meters (7.9 feet) and the height of its hips that was 0.7 meters (2.3 feet). Based on scans of the skull Coelurus had a rather large neck and torso because of its vertebrae that were long as well as a long, slim hindlimb because of its long metatarsus, as well as the skull was small and slender.

The skull is not known, except for possibly a small portion of lower jaw that was found in the same location as other pieces of Coelurus materials. While it is of the same color and preservation as fossils that are believed to be part of the Coelurus skeleton is extremely thin and could mean that it’s not part of the skeleton. This bone measures 7.9 centimeters in length (3.1 in) however it is it is only 1.1 centimeters in height (0.43 inches). The vertebrae were tall and long and had narrow neural spines that were low and thin walls around the vertebrae’s bodies. The neck vertebrae of the species were pneumatic, with a lot of hollow spaces along their surface (pleurocoels) and these hollows weren’t equally distributed across the vertebrae, and were different in size. The neck vertebrae were extremely long, with bodies that were four times wider than long and articulated with concave faces at both ends (amphicoely). The back vertebrae weren’t as long, and lacked hollows in the surfaces, and had concave faces that were less developed and bodies which were shape-like an hourglass. The tail vertebrae were also lacking hollows in the surfaces.

The only bone that is known of the shoulder girdle was a piece of the scapula. The upper arm had an distinct S-shaped curve from a side perspective and was slightly larger over the forearm (11.9 centimeters, versus 9.6 millimeters ). The wrist was an elongate carpal+, like that of Deinonychus as well as fingers that were both long and thin. The only bone that is known from the pelvic girdle was the paired and fused pubis bones with a distinctive lengthy “foot” at the end. The thigh bones were an S-shape at the rear. The metatarsals appeared to be unusually long and slim, almost the length of thigh bones (the longest thigh bone that is preserved measures 21 centimeters in length).

Coelurus was first described as early as 1879, in 1879 by Othniel Charles Marsh who was an American naturalist and paleontologist who was famous by his “Bone Wars” with Edward Drinker Cope. In the early days he simply identified what he believed to be vertebrae that came from the back and the tail that were found in the same spot as the prototype specimen of the new genus and species Camptonotus dispar (later changed its name to Camptosaurus because Camptonotus was used for crickets). Marsh was impressed by their hollow insides thin-walled vertebrae. This was the characteristic that earned the species the nickname: Coelurus fragilis. He conceived of his brand new species being one that was “animal about as large as a wolf, and probably carnivorous”. Coelurus was to become the first small theropod named in the Morrison Formation, although at the time Marsh was not sure that it was an animal. Marsh returned to the area in 1881, and provided drawings of bones with placing it in an entirely new order (Coeluria) and the family (Coeluridae).

From there, the tale gets more complicated. The remains of the skeleton were scattered throughout in the mine, and remains being discovered between September 1879 and September 1880. Marsh decided to put some of the remains in the new species C. Agrilis, based due to two pubic bones that he believed belonged to an animal 3 times bigger than C. fragilis. The genus was reintroduced in 1888, adding C”. the gracilis that is based on remains of unknown origin that are only known today through one claw bone that is related to a tiny theropod found in The Early Cretaceous Arundel Formation of Maryland. The species is not accepted as being a representation of Coelurus in studies of the genus. However, it is not assigned a specific Genus.

In spite of their professional rivalry, Cope also identified species as Coelurus and in 1887 Cope named fossils from that Late Triassic of New Mexico as C. bauri and C. longicollis. Then, he named them as their own genus Coelophysis.

It was in 1903 that Henry Fairfield Osborn named another species of small theropods of the Morrison Formation, Ornitholestes. The genus was named after an incomplete skeleton found in Bone Cabin Quarry, north of Como Bluff. Ornitholestes was linked to Coelurus in the year 1920, when Charles Gilmore, in his important research on theropod dinosaurs concluded that the two species were identical. The same conclusion was echoed in the literature for a long time. The two genera were never officially compared however, nor did there exist a complete accounting of what was actually belonging to Coelurus prior to John Ostrom’s research in the year 1980.

Gilmore believed Gilmore had suspected that C. fragileis and C. Agrilis were one and identical, however Ostrom could prove this asymmetry. This vastly expanded the knowledge of information on C. fragilis and Ostrom could prove that Ornitholestes was distinct from Coelurus. The time was when Dale Russell had proposed that C. is agilis was a species belonging to Elaphrosaurus based on the insufficient information he had published. Ostrom was capable of proving that this wasn’t the situation. In addition, he proved how one of three vertebrae Marsh had depicted in his study of C. fragilis actually was a combination of two vertebrae. The other that was proven to have come from a different quarry and not belonged to Coelurus but rather to an small theropod that was not named. This unnamed genus could not be the only small theropod found in the Morrison Formation to be confused with Coelurus A subsequent research (1995) from a partially-constructed skeleton found in Wyoming was initially believed to be a larger Coelurus specimen, but subsequent research revealed that it was part of an unrelated Genus, Tanycolagreus.

Source: Wikipedia