Name: Coelurus ‭(‬Hollow tail‭)‬.
Phonetic: See-lur-us.
Named By: Othniel Charles Marsh‭ ‬-‭ ‬1879.
Synonyms: Coelurus agilis,‭ ‬Elaphrosaurus agilis.
Classification: Chordata,‭ ‬Reptilia,‭ ‬Dinosauria,‭ ‬Saurischia,‭ ‬Theropoda,‭ ‬Coelurosauria,‭ ‬Coeluridae.
Species: C.‭ ‬fragilis (type).
Diet: Carnivore.
Size: Estimated to be about‭ ‬2.4‭ ‬meters long.
Known locations: USA,‭ ‬Wyoming‭ ‬-‭ ‬Morrison Formation.
Time period: Kimmeridgian of the Jurassic.
Fossil representation: Partial post cranial skeleton.

       Although only a little dinosaur,‭ ‬the taxonomic history of Coelurus can be confusing to say the least.‭ ‬The first small theropod dinosaur from‭ ‬the famous Morrison Formation to be named,‭ ‬in the past the genus Coelurus has crossed paths with other small Morrison formation theropods such as Ornitholestes and Tanycolagreus.‭ ‬In addition to this former Coelurus species named as C.‭ ‬bauri and C.‭ ‬longicollis were re-named as being Coelophysis,‭ ‬a much earlier theropod dinosaur.‭ ‬In short the only valid species of Coelurus at the time of writing is C.‭ ‬fragilis.‭ ‬Another former species,‭ ‬C.‭ ‬agilis that was once also described as a species of Elaphrosaurus is now considered to be a synonym to C.‭ ‬fragilis.
       Though small,‭ ‬Coelurus was elongated with a long neck thanks to the vertebrae that were also elongated.‭ ‬In addition to this general appearance,‭ ‬the rear legs were also very long and slender,‭ ‬indicating that Coelurus was both lightly built and very swift.‭ ‬It is likely that Coelurus was a predator of small vertebrates such as lizards and primitive mammals,‭ ‬but smaller ornithopod dinosaurs such as Dryosaurus and Othnielosaurus could also have been attacked,‭ ‬especially when sick or not yet fully grown.‭ ‬The speed that allowed Coelurus to be a hunter would have also been its best defence however,‭ ‬as larger theropod dinosaurs such as Ceratosaurus,‭ ‬Torvosaurus and Allosaurus are also known from the Morrison Formation,‭ ‬with Allosaurus being particularly common.
       Despite only now being known from a partial skeleton,‭ ‬the hollow nature of the tail which was the inspiration for the name Coelurus,‭ ‬has also been used to identify an entire group of theropod dinosaurs called the Coelurosauria.‭ ‬The Coelurosauria today branches off to include many of the more well-known theropod groups including the alvarezsaurs,‭ ‬ornithomimosaurs,‭ ‬therizinosaurs,‭ ‬dromaeosaurs,‭ ‬and most famous of all these,‭ ‬the tyrannosaurs.‭ ‬This is a stark contrast to when the Coelurosauria was first created to only include the small theropod dinosaurs,‭ ‬something that it is no longer used for.‭ ‬However,‭ ‬the partial nature of the only remaining Coelurus fossils means that there are still a lot of unanswered questions concerning exactly how the Coelurus genus was related to all these others.‭ ‬Unfortunately our ability to answer these questions depends entirely upon future fossil discoveries being made.

Further reading
-‭ ‬Notice of new Jurassic reptiles.‭ ‬-‭ ‬American Journal of Science,‭ ‬series‭ ‬3‭ ‬18:‭ ‬501‭–‬505.‭ ‬-‭ ‬Othniel Charles Marsh‭ ‬-‭ ‬1879.
-‭ ‬The dinosaurian genus Coelurus.‭ ‬-‭ ‬American Naturalist‭ ‬21:‭ ‬367‭–‬369.‭ ‬-‭ ‬Edward Drinker Cope‭ ‬-‭ ‬1887.
-‭ ‬On a new genus of Triassic Dinosauria.‭ ‬-‭ ‬American Naturalist‭ ‬23:‭ ‬626.‭ ‬-‭ ‬Edward Drinker Cope‭ ‬-‭ ‬1889.
-‭ ‬Coelurus and Ornitholestes:‭ ‬Are they the same‭? ‬-‭ ‬John H.‭ ‬Ostrom‭ ‬-‭ ‬In Aspects of Vertebrate History:‭ ‬Essays in Honor of Edwin Harris Colbert,‭ ‬Louis L.‭ ‬Jacobs‭ (‬ed‭) ‬-‭ ‬Flagstaff:‭ ‬Museum of Northern Arizona Press.‭ ‬pp.‭ ‬245‭–‬256‭ ‬-‭ ‬1980.
-‭ ‬A new skeleton of Coelurus fragilis from the Morrison Formation of Wyoming.‭ ‬-‭ ‬Journal of Vertebrate Paleontology‭ ‬18‭ (‬3,‭ ‬Suppl.‭)‬:‭ ‬64A.‭ ‬-‭ ‬Clifford A.‭ ‬Miles,‭ ‬Kenneth Carpenter‭ & ‬Karen Cloward‭ ‬-‭ ‬1998.
-‭ ‬Redescription of the small maniraptoran theropods Ornitholestes and Coelurus from the Upper Jurassic Morrison Formation of Wyoming‭ ‬-‭ ‬Kenneth Carpenter,‭ ‬Clifford Miles,‭ ‬John H.‭ ‬Ostrom‭ & ‬Karen Cloward‭ ‬-‭ ‬In The Carnivorous Dinosaurs,‭ ‬Kenneth Carpenter‭ (‬ed‭)‬.-‭ ‬Bloomington:‭ ‬Indiana University Press.‭ ‬pp.‭ ‬49‭–‬71‭ ‬-‭ ‬2005.


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