Name: Ceratosaurus
(Horned lizard).
Phonetic: See-rat-oh-sire-us.
Named By: Othniel Charles Marsh - 1884.
Classification: Chordata, Reptilia, Dinosauria,
Saurischia, Theropoda, Ceratosauria, Ceratosauridae.
Species: C. nasicornis (type),
C. dentisulcatus?, C. magnicornis?
Type: Carnivore.
Size: Certainly up to 6 meters long, larger
specimens indicate an upper size approaching at least 6.7 meters long.
Known locations: USA, Morrison Formation.
Portugal. Tanzania.
Time period: Kimmeridgian to Tithonian of the
Jurassic.
Fossil representation: Many specimens representing
several species.
Ceratosaurus
has been known to science since towards the end of the nineteenth
century, and thanks to its head ornamentation, has long been one of
the most popular. Early on, Othniel Charles Marsh considered the
blade like nasal horn to have been a weapon against other dinosaurs,
but this is no longer considered likely, especially when you compare
Ceratosaurus to other theropod dinosaurs that had
head crests such as
Dilophosaurus,
Monolophosaurus
and Guanlong
which are all more likely for a visual
display purpose.
Ceratosaurus also possessed a pair of smaller
crests
above its eyes that were extensions of the lacrimal bones.
The
distinctive nasal horn of Ceratosaurus was made
from an extension of
the nasal bones at the snout of the skull. The horn itself is not a
single growth but the fusing of two growths from separate bones. A
juvenile specimen also features the beginnings of the horn from these
two bones that have not yet fused together, possibly indicating that
the nasal horn, when grown, was a sign of reproductive maturity.
Another
interesting feature that seems to make Ceratosaurus
unique among the
theropods was the osteoderms that ran down its back. The purpose
for these is not exactly known. Osteoderms are often evolved as a
form of defence and if this were the case with Ceratosaurus,
then
that could suggest that there were other larger predators at the time
(possibly those like Saurophaganax)
that would not think twice about attacking Ceratosaurus.
It may have
also been for extra defence in intraspecific combat with rivals. The
tail of Ceratosaurus was quite flexible and
supported by high vertebral
spines. It has been suggested that if Ceratosaurus
ever took to the
water, the tail would have been a very powerful swimming aid, used
in a similar fashion as a crocodiles.
Ceratosaurus
is the type genus of the Ceratosauridae
group of theropod dinosaurs.
Further reading
- Principal characters of American Jurassic dinosaurs. Part VIII. The
order Theropoda. - The American Journal of Science, series 3
27:329-340. - Othniel Charles Marsch - 1884.
- Restorations of Claosaurus and Ceratosaurus.
- American Journal of
Science 44 (262): 343–349. - Othiel Charles Marsh - 1892.
- Osteology of the carnivorous Dinosauria in the United States National
Museum, with special reference to the genera Antrodemus
(Allosaurus)
and Ceratosaurus. - Bulletin of the United States
National Museum 110:
1–154. - C. W. Gilmore - 1920.
- Ceratosaurus (Dinosauria, Theropoda): A Revised
Osteology. - Utah
Geological Survey. pp. 1–80. - J. H. Madsen & S. P. Welles -
2000.
- A reanalysis of the phylogenetic affinties of Ceratosaurus
(Theropoda, Dinosauria) based on new specimens from Utah, Colorado, and
Wyoming. - Journal of Vertebrate Paleontology. 20. - B. B. Britt, D. J.
Chure, T. R. Holtz Jr, C. A. Miles & K. L. Stadtman - 2000.
- Ceratosaurus sp. (Dinosauria: Theropoda) in the
Late Jurassic of
Portugal. - 31st International Geological Congress. Rio de Janeiro,
Brazil. - O. Mateus & M. T. Antunes - 2015.
- New information on the forearm and manus of Ceratosaurus
nasicornis
Marsh, 1884 (Dinosauria, Theropoda), with implications for theropod
forelimb evolution. - Journal of Vertebrate Paleontology. 36 (2). - M.
T. Carrano & J. Choiniere - 2016.