Saturday, April 26, 2008

Ceratosaurus nasicornis

One of my all-time favourite theropod is for some reason Ceratosaurus nasicornis. You might think its the horns but I'm actually more drawn to the overall skull morphology. I can't remember now why but Ceratosaurus was one of the first theropods that I attempted to draw the skull of. So I guess it was the first theropod that I actually paid attention to the skull morphology in some detail...

In any case, Ceratosaurus is still a taxon of significance. It represents the diverse group of basal theropods otherwise known as Ceratosauria, though what constitutes the group has never been stable. Aside from Ceratosaurus, Ceratosauria has traditionally included such taxa as Elaphrosaurus, Dilophosaurus, Coelophysis, Syntarsus, abelisaurids and other "ceratosaurs". Recent work however seem to show Ceratosauria in this traditional sense to be unsupported. Most recent phylogenies would separate coelophysoids (Coelophysis, Syntarsus, possibly Dilophosaurus, etc.) from Ceratosauria but the exact taxonomic make up of Ceratosauria is still controversial. Thus a more inclusive definition is preferred - that is, Ceratosauria is all dinosaurs sharing a more recent common ancestry with Ceratosaurus than with birds.

Even then, the vast majority of ceratosaurs are abelisaurs anyway so I can't see why they can't just be called basal abelisaurs or something...Ceratosaurus itself seems to be very closely related to abelisaurs, an enigma as all abelisaurs (with the exception of Tarascosaurus) are known from the Cretaceous of Gondwana. But then again, Ceratosaurus is basal to abelisaurs and its earlier presence may just be that basal abelisaurs weren't necessarily restricted to Gondwana...but who knows, maybe we'll never know.

5 comments:

Traumador said...

As usual awesome drawing...

Quick question (if you don't mind my asking here) so Dilophosaur might NOT be a Ceolophysid? What would it be than if not part of that group?

Mambo-Bob said...

According to some studies, such as Carrano et al. (2002) Rauhut (2003), Dilophosaurus is not within a monophyletic Coelophysoidea but basal to the rest of the derived "ceratosaurs". However, other studies unite Dilophosaurus with Coelophysis, Syntarsus, Lilienstrernus, Lophostropheus, etc. in a monophyletic Coelophysoidea. The overall consensus supports this topology as well.

However, it is kind of odd that previous studies which have attempted to resolve "ceratosaur" phylogeny did not have a wide taxonomic coverage and the majority of more studies seem to be focused on the interrelationships among the abelisaurs rather than the basal "ceratosaurs".

Mambo-Bob said...

oops, that's "majority of more recent studies"...

Anyway, I think Dilophosaurus is a coelophysoid (based on the consensus of previous studies) - I just merely pointed out some controversial positions raised in previous studies.

Zach said...

Dilophosaurus is a giant coelophysoid. Actually, I think Gojirasaurus is of similar size. At any rate, I like the idea that coelophysoids and ceratosaurs (abelisaurs) are separate groups. The two look completely different, especially in the skull. I imagine that Ceratosaurus + Abelosauria sits just above ceolophysoids but below "megalosaurs."

I love the sketch. I like Ceratosaurus not really because of its horns, but because of its ridiculously large teeth! Gotta wonder what that sucker was eating with teeth like that. Maybe it was scavenging whatever Allosaurus was killing?

Mambo-Bob said...

Hey Zach,

I love your observations! I was going to comment on the ridiculously large teeth but completely forgot while I was writing...thank you for reminding me.

There have been several papers that mentioned in passing the large teeth in Ceratosaurus so I'll reread those and perhaps even start a new blog post about the that...