Superfamily Ceratosauroidea

family Ceratosauridae

Early Jurassic to Late Jurassic
(Sinemurian to Kimmeridgian/Tithonian)



Ceratosaurus nasicornis skeleton - length 6 meters
late Jurassic (Kimmeridgian)
image courtesy Professor Paul Olsen

My Linnean/Evolutionary Systematic sympathies are showing - I have used the term "Ceratosauroidea" rather than "neoceratosauria" to distinguish these large, persistantly primitive theropods from their Coelophysoid ancestors. Both Coelophysoidea and Ceratosauroidea/Neoceratosauria together from the Ceratosauria, the most primitive clade of "neotheropods" (conventional or non-herrasaur theropods). The Abelisaurs are often included here as well. These are united by a number of features, including a hand with four fingers (the fourth digit is present, although strongly reduced, in ceratosaurs, but absent in all more advanced theropods), the lightly-built jaw support bones and roof of the mouth, and the robust central metatarsal. and a number of more specialised features. However, the "neoceratosaurs" lack many of the skull specializations of the coelophysids, so it is possible that they may not be that closely related after all.

subfamily Ceratosaurinae

Ceratosaurus nasicornis Marsh, 1884b

Comments: Interesting because it is structurally so much more primitive than its allosaur contemporaries, this medium-sized theropod is characterised by its tall nose horn and smaller preorbital horns in front of the eyes. It also possesses a row of bony nodules down the spine, similiar to those of pseudosuchian thecodonts and the earliest dinosaurs. The skull lightly-constructed skull is armed with quite proportionally large teeth. It is unlikely this animal could bring down large game (in contrast to the Allosaurs); it probably preyed on smaller animals like ornithopods

Ceratosaurus magnicornis Madsen and Welles, 2000

Comments: Quoting Tim Williams:
"C. magnicornis is differentiated from C. nasicornis by proportional differences in the skull, vertebrae, and limb bones. It appears to be a more robust species compared to C. nasicornis. The nasal horn is longer, but lower than that of C. nasicornis, and the lacrimal "horns" [in front of the eyes] are better developed.
I suspect though that future studies on Ceratosaurus may sink C. magnicornis as a junior synonym of C. nasicornis....it is possible that the differences between C. magnicornis and C. nasicornis might be explained by intraspecific variation within a single Ceratosaurus species. Coelophysis bauri and Dilophosaurus wetherilli also show a lot of morphological variation among the specimens referred to each species."

Ceratosaurus dentisulcatus Madsen and Welles, 2000

Comments: A large ceratosaur. Quoting Tim Williams:
"C. dentisulcatus is the second new Ceratosaurus species named by Madsen and Welles. It appears to be more distinct from C. nasicornis than C. magnicornis is, and so can more reliably be considered a new species. It gets its species name by the distinct grooves (sulci) running down the length of the anterior teeth of the upper jaw. C. dentisulcatus also has fewer maxillary and dentary teeth, and the front of the dentary is strongly curved and upturned. There are also proportional differences in the elements of the skull (such as a lower snout) and postcranium compared to the two other North American Ceratosaurus species. The nasals and lacrimals are not preserved in C. dentisulcatus so its "horns" (assuming it had them) cannot be compared with the other two species."

?Ceratosaurus ingens (Janensch, 1920)

Comments: A huge animal, possibly a ceratosaur. All that is known are some distinctive ceratosaur teeth, but these are almost 15 cm long, the size of tyrannosaur teeth. Rowe and Gauthier (1990) argued that C. ingens and C. roechlingi lack diagnostic characters, and should best be regarded as nomina dubia (i.e. it is not possible to identify them properly). It is possible also too large to belong with Ceratosaurus, although it may be a related genus. But whatever it was, this superpreditor obviously preyed on the contemporay sauropod dinosaurs in its environment, perhaps by quick slashing bites rather the more powerful bites of an Allosaur.

Subfamily Sarcosaurinae

Little is known about this family. According to the hip characteristics, teh Sarcosaurines appears to be more advanced than Ceratosauridae, despite being much earlier in time. Sarcosaurus woodi is the only certain species. Genusaurus sisteronis Accarie, Beaudoin, Dejax, Fries, Michard, and Taquet, 1995 from the mid Albian of France is also placed here. Based on a partial skeleton, this species has many primitive features. However, it lived much later than Sarcosaurus, and although the two are generally included together, I remain sceptical until more information comes to light.

Sarcosaurus woodi Andrews, 1921

Comments: Based on poor and fragmentary remains, this small theropod seems to be is very much like Ceratosaurus. The more dorsal placement of the otherwise similiar femoral outer ridges imply this may be a more advanced species than Ceratosaurus, despite the latter's much later age. There may recently have been a skull found that belongs to this animal.

Links

by Professor Paul Eric Olsen, part of DINOSAURS AND THE HISTORY OF LIFE - GEOLOGY V1001x

Ceratosauria - Palaeos

Ceratosauria - - Justin Tweet's Thescelosaurus! pages

Neoceratosauria by T. Mike Keesey - definition of the group and list every known species. Shows Ceratosaurus related to the Abelisauria - although this is by no means certain.

Jurassic Gallery - fantastic artwork by M. Shiraishi. By Japanese and English

Ceratosauria Mikko's phylogeny site

Gregory S. Paul, Predatory Dinosaurs of the World Simon and Schuster, 1988

Rowe, T., & Gauthier, J., 1990: Ceratosauria. 151-168 in Weishampel, D. B., Dodson, P., & Osmólska, H. (eds.), 1990: The Dinosauria, University of California Press, Berkley, Los Angeles, Oxford

Madsen Jr., J.H. and Welles, S.P. , 2000. Ceratosaurus (Dinosauria, Theropoda), a revised osteology. Utah Geological Survey Miscellaneous Publications (MP-00-2): 80 p.

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