Sunday, March 9, 2014

Ceratosaurus: Prehistoric Animal of the Week

This week we shall be looking at a theropod with some truly unique features.  Enter Ceratosaurus nasicornis!

Ceratosaurus nasicornis by Christopher DiPiazza

Ceratosaurus was a meat-eating dinosaur that lived during the late Jurassic, about 150 millon years ago in what is now Utah and Colorado, USA.  As an adult it would have measured about twenty feet from nose to tail.  Ceratosaurus translates to "Horned reptile/lizard" and refers to the horn-like protrusion on the animal's snout.  This was in fact, not really a horn as much as it was a crest.  Originally scientists believed this dinosaur would have used that little bump as a weapon.  Problem is it is just way too thin and delicate for that sort of rough-housing.  Since then, most paleontologists agree that it was most likely just a display adaptation. It also had two smaller bony crests in front of its eyes. 

Bronze cast of a Ceratosaurus skull on display at the Mesalands Dinosaur Museum in Tucumcari new Mexico.

In addition to the horns, Ceratosaurus had a few other unique characteristics amongst theropod dinosaurs.  It had a row of small bony plates, called osteoderms, running down the center of its back.  Its tail was particularly deep and flattened laterally, leading some scientists to believe that Ceratosaurus may have been a decent swimmer. (although there is little other evidence that suggests this)  It had short, powerful arms with four fingers on each hand and its teeth were the longest proportionally to the rest of its body out of any dinosaur.  All of this leaves us with a cool, yet strange theropod.

Almost-complete(no arms!) Ceratosaurus skeletal mount on display at the National Museum in Washington D.C..  Note the small osteoderms over the back.

 Ceratosaurus bones have been found in the same formations as other, larger Jurassic meat eaters, like Allosaurus and Torvosaurus.  Most scientists agree that Ceratosaurus may have specialized in hunting a different kind of prey than its giant contemporaries, perhaps going after smaller animals, rather than giant sauropods and heavily-armed stegosaurs.  This is further supported by the fact that Ceratosaurus bones are particularly less common than most of the other dinosaurs known from the Late Jurassic of North America.  This could mean that Ceratosaurus typically lived in habitats different from the rest of those dinosaurs where fossilization didn't take place as easily.

Sometimes I wonder what exactly prevented Ceratosaurus from existing close to the other megapredators of it's time...

Allosaurus: Ceratosaurus, you’re eating an ornithopod.  It’s Monday.
Ceratosaurus: So?
Torvosaurus: So that’s against the rules and you can’t sit with us.
Ceratosaurus: Whatever!  Those rules aren’t real.
Torvosaurus: They were real that day I ate a dead turtle!
Ceratosaurus: Because that turtle was disgusting.
Allosaurus: YOU CAN’T SIT WITH US!

They said it couldn't be done but I managed to make a cartoon merging Late Jurassic megapredators with Mean Girls.  It wasn't even that hard.

That's all for this week!  As always feel free to comment below or on our facebook page.  Want to see a particular prehistoric beastie reviewed?  Let me know and I'll make it happen!

Works Cited

Foster, John (2007). "Gargantuan to Minuscule: The Morrison Menagerie, Part II". Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. pp. 162–242. ISBN 0-253-34870-6.

Gilmore, C.W. (1920). "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.

Marsh, O.C. (1884). "Principal characters of American Jurassic dinosaurs, part VIII: The order Theropoda". American Journal of Science 27 (160): 329–340.

Rowe, T.; Gauthier, J. (1990). "Ceratosauria". In Weishampel, D.B.; Dodson, P.; Osmólska, H. The Dinosauria. University of California Press. pp. 151–168. ISBN 0-520-06726-6.


  1. In reference to the "Ceratosaurus bones" paragraph, I'm surprised you didn't cite Bakker & Bir 2004, given that it covers all that & more (See the Bakker/Bir quote). Also, for once, I'm glad I saw "Mean Girls" just so I could get the cartoon's reference, although that does make me wonder how a Ceratosaurus became the leader of a group of LJ megapredators AWA what that makes Linsey Lohan?


    Quoting Bakker/Bir ( ): "Ceratosaurids have been portrayed as hunters of sauropods, camp- tosaurs, and stegosaurs (Gilmore 1920). Como shed teeth indicate that these views are unbalanced. For two decades, the senior author has been puzzled by a sector of ceratosaur anatomy: the tail is shaped more like a crocodilian's than is any other well-known theropod. Ceratosaurids have very tall neural spines in the anterior caudal vertebrae, and the spines are nearly vertical, lacking the strong backward slant of allosaurs and megalosaurs. The chevrons too are very deep, so the tail profile agrees with that of freshwater crocodilians today (Gilmore 1920; fig. 14.1). All theropods could swim. Powerful kicks from the hind legs, plus sinuous swooshing from the tail could propel allosaur- ids through the water. But the shallow neural spines and chevrons, the stiffening effect of the posterior zygapophyses, and the short, stiff torso would make allosaurs poorer swimmers than ceratosaurids. Therefore we predict that ceratosaurid shed teeth would be most common mingled with aquatic carcasses.
    This prediction is fulfilled (fig. 14.13). Most ceratosaurid shed teeth are from Surf sites. The abundance of small juvenile teeth, with a few full-grown teeth, suggests that ceratosaurid parents fed near the youngsters; perhaps the adults hunted the biggest lungfish and crocodiles and dragged the carcasses back to a shoreline lair. One adult shed tooth is from a Dry Turf sauropod site; two Wet Turf sites have juvenile and adult teeth mixed with sauropod carcasses. These data indicate that Ceratosaurus at Como had potential for feeding on large dinosaurs but was specializing in aquatic prey."

  2. "Also, for once, I'm glad I saw "Mean Girls" just so I could get the cartoon's reference,"

    For once? That movie rules.

    "although that does make me wonder how a Ceratosaurus became the leader of a group of LJ megapredators AWA what that makes Linsey Lohan?"

    In Girl World the leader can be ANYONE O.o lol don't look/read too far into it.

    "I'm surprised you didn't cite Bakker & Bir 2004, given that it covers all that & more"

    I know what you are talking about but Bakker's theories are VERY specific as you can see from the quote you put up. I touched on the possibility of it being associated with water more than other big theropods. I'm happy to leave it at that.

    Thanks for the comment!

    1. "For once? That movie rules."

      I say that b/c it's 1 of my guilty pleasures.

      "I know what you are talking about but Bakker's theories are VERY specific"

      Fair enough.