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.