Historically it was long thought that the Upper Triassic Coelophysis Quarry at Ghost Ranch New Mexico contained, with the exception of an odd phytosaur, almost exclusively skeletons of the neotheropod dinosaur Coelophysis bauri. However, the recent discoveries of Effigia and Vancleavea demonstrate a much greater diversity of vertebrates present in the quarry. Now we can add to the list a second theropod dinosaur. Daemonosaurus chauliodus ('prominent toothed demon reptile') is known from only a single skull and several associated vertebrae found in the Carnegie Museum block (C-4-81) collected from the quarry in the early 1980s.
Daemonosaurus differs from Coelophysis bauri in the presence of the extreme protruding teeth, a significantly larger prefrontal, and in the dorsoventrally deep premaxilla. A phylogenetic analysis of basal dinosaurs recovers Daemonosaurus outside of Neotheropoda as the sister taxon to Tawa hallae + Neotheropoda.
One possibility I find interesting is that we now have four theropods known from the Upper Triassic in the Ghost Ranch area, Tawa, a coelophysoid, and Chindesaurus from the Hayden Quarry (Petrified Forest Member) and Coelophysis and Daemonosaurus from the Coelophysis Quarry (siltstone member). Currently Chindesaurus lacks a preserved cranium, whereas Daemonosaurus is known almost exclusively from the skull. Thus, it is possible that they could represent the same or a similar taxon. Only the discovery of more complete material of either taxon can test this idea.
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| Holotype specimen of Daemonosaurus chauliodus in left lateral view |
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| Life reconstruction of Daemonosaurus chauliodus by Jeff Martz |
Abstract - The oldest theropod dinosaurs are known from the Late Carnian of Argentina. However, the evolutionary diversification of this group after its initial radiation but prior to the Triassic–Jurassic boundary is still poorly understood because of a sparse fossil record near that boundary. Here, we report on a new basal theropod, Daemonosaurus chauliodus gen. et sp. nov., from the latest Triassic ‘siltstone member’ of the Chinle Formation of the Coelophysis Quarry at Ghost Ranch, New Mexico. Based on a comprehensive phylogenetic analysis, Daemonosaurus is more closely related to coeval neotheropods (e.g. Coelophysis bauri) than to Herrerasauridae and Eoraptor. The skeletal structure of Daemonosaurus and the recently discovered Tawa bridge a morphological gap between Eoraptor and Herrerasauridae on one hand and neotheropods on the other, providing additional support for the theropod affinities of both Eoraptor and Herrerasauridae and demonstrating that lineages from the initial radiation of Dinosauria persisted until the end of the Triassic. Various features of the skull of Daemonosaurus, including the procumbent dentary and premaxillary teeth and greatly enlarged premaxillary and anterior maxillary teeth, clearly set this taxon apart from coeval neotheropods and demonstrate unexpected disparity in cranial shape among theropod dinosaurs just prior to the end of the Triassic.
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| skeletal outline of Daemonosaurus chauliodus with a human for scale |
The Coelophysis Quarry is several million years younger than the Hayden Quarry. Also, the coelophysid in the Hayden Quarry has never been called Coelophysis proper, and we see some differences with C. bauri. Finally, the paper points out that the cervical vertebrae of Daemonosaurus differ from the one cervical preserved in the type specimen of Chindesaurus bryansmalli. It could be likely though that the two will eventually found to form a clade.
ReplyDeleteGot me on Coelophysis from the Hayden Quarry. Coelophysoid then. The only preserved Chindesaurus cervical is probably from the posterior portion of the neck so there is probably no overlap. Just some interesting food for thought.
ReplyDeleteAlso, the analysis has it as sister to Tawa + Neotheropoda, not just Tawa.
ReplyDeleteSterling thinks of the best dinosaur names.
ReplyDeleteHe's the one that thought of Tawa right?
Eric,
ReplyDeleteI'm not sure who came up with the name.
Jeff,
Congrats on your reconstruction making the front page of cnn.com. You are mainstream now.
I don't know who came up with Daemonosaurus. Actually, as a Tawa co-author, I can't remember for sure who came up with the genus name either! I think it might have been Alan Turner, but could easily be wrong. I know the species name was a consensus decision among everyone.
ReplyDeleteJust... one thing... will people please stop pretending that Greek sauros means "reptile"? It means "lizard". There was no such concept as "reptile". And yes, Owen really believed that his Dinosauria were lizards in a wide sense.
ReplyDeleteFor "creepy-crawly" (which is what "reptile" etymologically means), try herpeton, which is widely used in genus names of salamanders and Paleozoic limbed vertebrates, and which is of course what herpetology is named after.
@220mya
ReplyDeleteVery glad to hear that differences exist between Chindesaurus and Daemonosaurus chauliodus. It is too lovely a name to synonymized into nothingness.
@Jeffrey W. Martz
I second that kudos on your work! In addition to your own popularization, the popularization of protofeathered basal theropods --indeed ornithodires--is always a good thing in my book.
Won't be long until the Chinle or Moenkoepi cough up a few quills [fingers crossed].
Actually stratigraphic, and hence presumed temporal, criteria for separating taxa are unreliable using a morphological approach. Hasn't everyone recently been ripping apart Greg Paul for doing this (among other things)?
ReplyDeleteAll I'm suggesting is that presently we cannot discount that Daemonosaurus may turn out to be a Chindesaurus-like form until we find the skeleton of Daemonosaurus or a skull of the Chindesaurus.
The lone cervical vertebra of Chindesaurus is a piece of evidence that they may not be exactly the same, but we don't know if we are looking at homologous vertebrae (i.e., anterior vs. posterior).
Stratigraphic position alone should never be used to justify taxonomic separation, and I would never advocate that. However, it is an interesting observation that although the same tetrapod clades are found in both the Petrified Forest Member and overlying siltstone member at Ghost Ranch, in no case that I can think of, are the same species found in both members. This of course does not mean that there aren't some species that are found in both the Petrified Forest and siltstone members.
ReplyDeleteYou are correct that we don't know the exact vertebral position for the single cervical vertebra from the holotype of Chindesaurus. The features that differ between Daemonosaurus and Chindesaurus largely relate to the morphology and shape of the pneumatic pleurocoel. At least in other basal theropods that we have a good cervical series from (e.g., Tawa and Coelophysis bauri), the shape of the pleurocoel does not vary much through the cervical column, only its presence/absence and size.
In summary, we can't falsify the hypothesis that Chindesaurus and Daemonosaurus are synonymous, but there does seem to be some circumstantial evidence against the hypothesis.
Agreed.
ReplyDeleteThe article is freely downloadable from Royal Society Publishing. I have added the link after the reference.
ReplyDeleteGood to see this published after the intriguing SVP abstract. While I have no opinion on the proposed synonymy with Chindesaurus, I did note yesterday when checking theropods for cervical pleurocoel number that some do change shape throughout the series. For example, Chure (2000) states than in Allosaurus the pleurocoel "is oval on cervical three, reniform on cervicals five through eight and triangular on cervical nine."
ReplyDeleteMickey,
ReplyDeletePlease read my post carefully. I was only talking about basal theropods, not tetanurans. And thats not to say there's no shape change in basal taxa, just very little compared to what is seen in some more derived taxa.
In french they use the term ”dent de lapin” which describe an animal prominent toothed as a rabbit could have.
ReplyDeletehttp://forums.futura-sciences.com/newreply.php?do=newreply&noquote=1&p=3507997
Buck-toothed seems to be either an abuse of language as they don’t look alike what they try to describe on morphology basis.
These terms shoudn't be used to describe this animal as you could see further arguments here: http://qilong.wordpress.com/2011/04/15/buck-teeth-wait-a-minute/
Thanks for the update on the Ghost Ranch Theropoda et al, just what I was looking for - much appreciated.
ReplyDelete@micropion,
ReplyDeleteI was just having some fun...
Bill,
ReplyDeleteNot sure why nobody has mentioned this before.
Daemonosaurus may turn out to be less of an autapomorphic oddity and more of a key transitional fossil. The most parsimonious comparisons can be made to Heterodontosaurus and Massospondylus kaalae, basal members of the Ornithischia and Sauropodomorpha respectively. Short, round rostrum, enlarged premaxillary teeth. And in the case of Heterodontosaurus, both share a large postnarial process of the premaxilla, a trait not seen in any saurischian dinosaur. On that point, the supposed large postnarial process on Herrerasaurus may be a mistake. It appears to have a smaller one.
Daemonosaurus is the long sought key taxon uniting the three major dinosaurian clades, IMHO.
Illustrations of these hypotheses can be seen at reptileevolution.com/daemonosaurus.htm and links therein.
Best regards,
David Peters