The Demon of the Chinle

Very rarely do you get to just shove your hand deep into the Mythology Pool and pull out a name like Daemonosaurus. Just last year, there was Diabloceratops, a ceratopsian with a very horny appearance. The [fittingly] named Moloch horridus, a nomen that has lent its seeming to another dinosaur, Stygimoloch. There’s a couple fish with names like Satanoperca, Lucifer or Mephisto; a frog bearing the popularly-Googled Beelzebufo; the ichnite burrow trace Daimonelix (“demon helix,” after the popular phrase for these fossils, “Devil’s corkscrew”). Curiosities of Biological Nomenclature has a bunch more. The latest has a wicked set of teeth, and the author’s were dutifully reminded that there need to be more “devils” and “demons” in the nomenclature business. Hence, Daemonosaurus chauliodus.

CM 76821, skull and anterior cervical vertebrae with cervical ribs of Daemonosaurus chauliodus (Sues et al., 2011). Top row, left and ride sides of the slab bearing the skull; middle row, interpretive drawing of the slab; and bottom, interpretive reconstruction of skull. Modified from Sues et al. (2011).

But there’s more going on beneath the surface. While normally I would talk about the phrase “chauliodus” (prominent teeth, an allusion to the very large anterior set) — which I will, but not yet — another thing comes up instead. Thus this post will talk about that other peculiarity of the skull, its shape.

Generally, theropods have long skulls, and the snout is usually at least over half of the length of the skull. The orbit is rarely, if ever, in the middle of the skull. This is normally supplemented by a long nasal and a long maxilla. But here, the maxilla and jugal, the nasal and frontal, are sets of bones almost equal in length, the snout is short, the skull is triangular, and the orbit (eye-socket) is HUGE. This skull looks like that of a juvenile. It could be that this specimen represents a juvenile animal. What does that then tell us about the validity of this animal? I previously remarked on the viability of juveniles here (on Raptorex kriegsteini) and here (on a new specimen of Tarbosaurus bataar) and here (on Brontomerus mcintoshi), and the general concensus is that we should refrain from using juveniles as holotypes because they typically will lack the features diagnostic of adults. In some cases, you can differentiate juveniles — lambeosaur juveniles can be distinguished as soon as their cranial crests begin growing, as the pattern of the nasals and premaxillae overlapping one another is distinctive and diagnostic among them in Lambeosaurus, Hypacrosaurus and Corythosaurus, all of them having similarly shaped crests at the same age (Evans, 2010). You can even tell Hypacrosaurus stebingeri from Hypacrosaurus altispinus in this fashion (Brink et al., 2011):

Lambeosaur ontogeny by specimens. Top row, Corythosaurus casuarius; middle row, Hypacrosaurus altispinus; bottom row, Lambeosaurus lambei. Differentiation becomes clear only during the subadult stage (third skulls in all series). Scale bar below top row equals 20 cm. After Evans, 2010.

Hadrosaurs are typically long-snouted, even at a young age, but theropods … not so much.

Byronosaurus jaffei skulls. A, MPC-D 100/972, a perinate skull. B, MPC-D 100/983, the holotype. The braincase and rostrum in lateral view were separate, although elements are preserved that include the posterior palate, they are not shown. Scale bar equals 1 cm. A after Bever and Norell (2009) and B after Makovicky et al. (2003).

Here, the snout does not change so much in depth as increase (massively) in length, although in this taxon this is an extreme, it’s been noted in other theropods as well.

Daemonosaurus chauliodus indicates a short-faced animal, seemingly still quite juvenile, and one might be taken to accept this as fact upon seeing it. The skull even exhibits open sutures in several braincase elements. But the story is not so simple. Vertebral fusion is often used as a key element of assessing ontogeny. In crocodilians, the vertebrae fuse together from the end of the tail towards the skull, and relative fusion of the vertebral column can be a proxy for age (Brochu, 1996). Five cervical vertebrae are exposed in CM 76821, holotype of Daemonosaurus chauliodus, and of these, the first three (atlas, axis, and CV1) are exposed well-enough to show the neurocentral suture, or what there is of it. As it is, this suture is closed in these vertebrae, which is an indication of skeletal maturity. While Sues et al. (2011) do not fully advocate that the specimen is adult, it is old enough to exhibit features that, in at least theropods, the apomorphies of the specimen are useful enough to differentiate it.

And just look at those teeth!

Let us briefly note that the phrase “daemon” is simply a fanciful way to transcribe the popular English “demon” as from the Greek δαίμον (daimon), which was something of a trickster spirit, but not necessarily evil; rather, it gets the “evil” reputation from the influence of Christian influence on treating the myths and folklore of other religions and cultures as influences of its own evil forces: the daimonai of Greek and daemona of Roman culture became true devils, spawn of Satan, and essentially synonymous with The Devil. Perhaps, then, we can call it the “prominent-toothed trickster reptile.” Besides, I’ve seen more wicked teeth on a dirk-toothed Smilodon populator.

Okay, I want to say more about some of the things I’ve mentioned so far, and I will, but that will have to stand for later.

Note: I had originally written this post back in March, so it as it’s now nearly November, much of the discussion is a tad dated (while the edition is printed (and online posted) as November, 22, it is essentially “out” and the name is technically now available for use). I am leaving the post as is. I’d like to add that the interesting aspect here is that despite extensive sampling and assessing material for decades, or a centruy, new things can still pop up and surprise us, or allow us to shake our foundations on what we consider to be “consistent” with previous professed ideas. One of the major themes of this blog has been t defy expectations from the professed experts as well as from outsiders (like myself) and challenge the idea that we “know” a thing we argue about. It is why I am so adamant when I discuss the properties of belief in connection with scientific discovery. Recovery of Daemonosaurus chauliodus in a block that has been known and examined since its recovery from the Coelophysis Quarry near Ghost Ranch, New Mexico, in 1947 by famed paleontologist Edwin Colbert, and it helps shake up the assumptions that things are ever settled, even when such new data comes in (and in this I tend to point my shaking finger at arguments such as Jack Horner’s “There are far, far fewer taxa than we assume” statements.

Bever, G. A. & Norell, M. A. 2009. The perinate skull of Byronosaurus (Troodontidae) with observations on the cranial ontogeny of paravian theropods. American Museum Novitates 3657:1-51.
Brink, K. s., Zelenitsky, D. K., Evans, D. C., Therrien, F. & Horner, J. R. 2011. A sub-adult skull of Hypacrosaurus stebingeri (Ornithischia: Lambeosaurinae): anatomy and comparison. Historical Biology 23(1):63-72.
Brochu, C. A. 1996. Closure of neurocentral sutures during crocodilian ontogeny: implications for maturity assessment in fossil archosaurs. Journal of Vertebrate Paleontology 16(1):49–62.
Evans, D. c. 2010. Cranial anatomy and systematics of Hypacrosaurus altispinus, and a comparative analysis of skull growth in lambeosaurine hadrosaurids (Dinosauria: Ornithischia). Zoological Journal of the Linnaean Society 159:398-434.
Makovicky, P. J., Norell, M. A., Clark, J. M. & Rowe, T. 2003. Osteology and relationships of Byronosaurus jaffei (Theropoda: Troodontidae). American Museum Novitates 3402:1-32.
Sues, H.-D., Nesbitt, S. J., Berman, D. S. & Henrici, A. C. 2011. A late-surviving basal theropod dinosaur from the latest triassic of North America. Proceedings of the Royal Society of London, B 278:3459-3464.

About these ads
This entry was posted in Paleontology, Science Reporting and tagged , , . Bookmark the permalink.

One Response to The Demon of the Chinle

  1. Pingback: A Skull Reconstruction for Daemonosaurus | The Bite Stuff

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s