Tetrapod Zoology

i-53d3d2710cbae8bff1cbea7e2f0b9a01-KG Ceratosaurus skull.jpg

One of my most favourite dinosaurs has always been Ceratosaurus but, given that I mostly work on Lower Cretaceous dinosaurs, I’ve never had the chance to look at it much (Ceratosaurus is Upper Jurassic). Imagine my surprise then when, during a recent visit to Glasgow (Scotland), I was confronted with a complete mounted (replica) skeleton of this neat beast at Kelvingrove Art Gallery and Museum. First named by Othniel Marsh in 1884, Ceratosaurus is best known for the type species, C. nasicornis from the Morrison Formation of Colorado…

Less well known is that two additional Morrison Formation species were named in 2000: C. magnicornis, named for its particularly big horns, and C. dentisulcatus, characterised by unusual elongate pockets located next to the keels on its teeth (Madsen & Welles 2000). These two might be distinct species, but it’s also possible that C. magnicornis at least might simply be a growth phase (a big male for example) of C. nasicornis. Furthermore, Ceratosaurus is not unique to the USA, but is also known from Upper Jurassic deposits in Portugal, Switzerland and Tanzania. The Portugese remains have most recently been identified as referable to C. dentisulcatus (Mateus et al. 2006) meaning that – if correctly identified – this species had an intercontinental range during the Tithonian. That’s a really big deal for lots of reasons. Several other species names have been proposed for Ceratosaurus specimens, but none are currently regarded as valid.

i-fa54bf764e21ad7e75327fa35908f624-Ceratosaurus USNM.jpg

Often regarded as phylogenetically isolated (albeit close to the ancestry of abelisaurs), it was recently argued that Genyodectes serus from the Aptian-Albian Cerro Barcino Formation of Chubut Province in Argentina might be a close relative of Ceratosaurus, the two forming a clade Ceratosauridae (Rauhut 2004). Sarcosaurus from England, once mooted as a small, Lower Jurassic ceratosaurid, has more recently been argued to be a coelophysoid (Carrano & Sampson 2004, Naish & Martill 2007) [adjacent image is old photo showing C. nasicornis as mounted in the Smithsonian Institution].

i-77c1eac6b4e94ea8ac8e4ba16d0087fb-AMNH C. nasicornis skull.jpg

Why is Ceratosaurus so cool? It doesn’t just have a nasal horn; it also sports large preorbital horns, and note that its nasal horn is actually positioned quite far back relative to the snout tip. Its skull is particularly deep and its maxillary teeth are particularly big, as are the dentary teeth. In a recently discovered, but as yet undescribed, juvenile specimen, the teeth are reported to be so long that their tips extend beyond the ventral edge of the lower jaw when the mouth is closed (similarly proportionally long teeth are present in some other theropod juveniles actually). These features all imply that Ceratosaurus was an adept macropredator, and perhaps it avoided competition with the more abundant Allosaurus by specialising on different (larger?) prey (Henderson 2000). Paradoxically though, the back of the skull looks very lightly constructed, with an immense laterotemporal fenestra; the postorbital bar (formed by the postorbital and jugal) is really gracile, and the mandible is both shallow and slightly curved along its length.

i-81478cb9c8352921ca28bdc166f5ae53-KG Ceratosaurus rostral.jpg

Uniquely amongst theropods, Ceratosaurus had a continuous row of bony scutes running along its neck, back and tail. It wasn’t that big – less than 7 m long and less than a ton in weight. Because Ceratosaurus is, morphologically, an archaic theropod compared to its tetanuran contemporary Allosaurus, Greg Paul (1988) likened it to a thylacine* surrounded by dingoes, which I kind of like. Incidentally, as a kid I recall reading a book which argued that Ceratosaurus and Allosaurus were the same species, with the smaller, horned Ceratosaurus being the male. This idea is patently ludicrous (the two are totally different animals, anatomically disparate in every conceivable detail), and unfortunately – or fortunately – I cannot recall the book in question [in adjacent image of the display at Kelvingrove, note how narrow the skull is. You can also see the furcula].

* Thylacine is spelt ‘thycaline’ in the relevant bit of text however (p. 276).

Finally, why on earth is Ceratosaurus displayed at a Scottish museum? Various bits and pieces from Jurassic rocks of Scotland have been identified as belonging to coelophysoids. Coelophysoids and ceratosaurids (and abelisaurs) have been united by some theropod workers in a group termed Ceratosauria. So whereas it would have been most appropriate to showcase a Coelophysis skeleton, the museum – I assume – went for the most charismatic member of Ceratosauria. New data, new analyses and new taxa nowadays seem to show that Ceratosauria is not monophyletic… nor is Coelophysoidea… but I’ll have to leave that to another time [very nice image below borrowed from wikipedia].

i-7f5b529fb5cf4f3b1b0c791250c32371-Ceratosaurus_nasicornis from wikipedia.jpg

Refs – –

Carrano, M. T. & Sampson, S. D. 2004. A review of coelophysoids (Dinosauria: Theropoda) from the Early Jurassic of Europe: with comments on the late history of the Coelophysoidea. Neues Jahrbuch fur Geologie und Paläontologie, Monatshefte 2004, 537-558.

Henderson, D. M. 2000. Skull and tooth morphology as indicators of niche partitioning in sympatric Morrison Formation theropods. Gaia 15, 219-226.

Madsen, J. H. & Welles, S. P. 2000. Ceratosaurus (Dinosauria, Theropoda) a revised osteology. Utah Geological Survey Miscellaneous Pubication 00-2, 1-80.

Mateus, O., Walen, A. & Antunes, M.T. 2006. The large theropod fauna of the Lourinhã Formation (Portugal) and its similarity to the Morrison Formation, with a description of a new species of Allosaurus. New Mexico Museum of Natural History and Science Bulletin 36, 1-7.

Naish, D. & Martill, D. M. 2007. Dinosaurs of Great Britain and the role of the Geological Society of London in their discovery: basal Dinosauria and Saurischia. Journal of the Geological Society, London 164, 493-510.

Paul, G. S. 1988. Predatory Dinosaurs of the World. Simon & Schuster, New York.

Rauhut, O. W. M. 2004. Provenance and anatomy of Genyodectes serus, a large-toothed ceratosaur (Dinosauria: Theropoda) from Patagonia. Journal of Vertebrate Paleontology 24, 894-902.

Comments

  1. #1 Zach Armstrong from Minne-snow-ta!
    December 8, 2007

    What, no Ceratosaurus ingens from PDW?! Nice post, Ceratosaurus is my favorite theropod. When I was young I would search every where for a good reconstruction, then I happened upon Paul’s PDW at amazon.com and…problem solved! What about…Proceratosaurus, even though it isn’t closely related, it still is cool.

  2. #2 Brian
    December 8, 2007

    Didn’t Bakker propose that Ceratosaurus was a hunter on lungfish? I do think it would fit the large teeth in combination with a weak bite.
    Perhaps this is one of Bakker’s more realistic ideas?

  3. #3 Brian
    December 8, 2007

    Didn’t Bakker propose that Ceratosaurus was a hunter on lungfish? I do think it would fit the large teeth in combination with a weak bite.
    Perhaps this is one of Bakker’s more realistic ideas?

  4. #4 Darren Naish
    December 8, 2007

    A-ha – excellent questions. I avoided discussion of C. ingens and the other species because (as usual) I was in a hurry. Originally Megalosaurus ingens, this tooth-based taxon was later suggested to be referable to Ceratosaurus by Paul (1988) and Rowe & Gauthier (1990). If it is a ceratosaurid, it would be a very big one (I’ve seen the type tooth: it’s currently on display in the NHM. Incidentally there is a good photo of it in Charig’s A New Look at the Dinosaurs). However, no-one has yet given any good reasons as to why it might be from a ceratosaurid… Madsen & Welles (2000) thought that this was probably an error, but apparently only because it seems too big, and that’s hardly compelling. Someone needs to have a long hard look and sort this out.

    And, yes, Bakker (and Gary Bir) have regarded Ceratosaurus as an amphibious swimming theropod that specialized on giant lungfish (see Bakker & Bir (2004), their chapter in Feathered Dragons). Sure, Ceratosaurus might have been a reasonable swimmer (its tail is deep and quite flexible), but there is little reason to take this seriously. Their argument mostly comes from the association of Ceratosaurus teeth with lungfish remains. Well, many terrestrial animals feed on fish an awful lot (perhaps even exclusively).

    I’d maybe be less sceptical if Bakker didn’t have a history of claiming that big theropods were amphibious swimmers: in the Edmarka paper, Bakker et al. (1992) propose that carcharodontosaurids and spinosaurines were amphibious marine animals, likened to basilosaurids!!

    Refs – –

    Bakker R. T. & Bir, G. 2004. Dinosaur crime scene investigations. In Currie P. J., Koppelhus, E. B., Shugar, M.A. & Wright, J. L. (eds) Feathered Dragons. Indiana University Press, pp. 301-342.

    – ., Kralis, D., Siegwarth, J. & Filla, J. 1992. Edmarka rex, a new, gigantic theropod dinosaur from the middle Morrison Formation, Late Jurassic of the Como Bluff outcrop region. Hunteria 2 (9), 1-24.

    Madsen, J. H. & Welles, S. P. 2000. Ceratosaurus (Dinosauria, Theropoda) a revised osteology. Utah Geological Survey Miscellaneous Pubication 00-2, 1-80.

    Paul, G. S. 1988. Predatory Dinosaurs of the World. Simon & Schuster, New York.

    Rowe, T. & Gauthier, J. 1990. Ceratosauria. In Weishampel, D. B., Dodson, P. & Osmólska, H (eds) The Dinosauria (University of California Press, Berkeley), pp. 151-168.

  5. #5 Zach Miller
    December 8, 2007

    He did indeed! That paper is in “Feathered Dragons” (an edited volume). Bakker suggests that Ceratosaurus went after man-sized lungfish in the Morrison, even going as far as to say that their tails were crocodile-like and good for swimming. Not sure how much I buy it, but it’s an interesting idea.

    Darren, check your email. And what’s this about coelophysids and ceratosaurs being paraphyletic?

  6. #6 Mike Keesey
    December 8, 2007

    More accurately, coelophysoids are not ceratosaurs and dilophosaurids are not coelophysoids or ceratosaurs. Ceratosauria and Coelophysoidea are still monophyletic–they’re just non-overlapping and less inclusive than once was thought.

    On another note, was anyone else disappointed by the craptastic (and very briefly-appearing) Ceratosaurus in Jurassic Park III?

  7. #7 Nagi
    December 8, 2007

    “On another note, was anyone else disappointed by the craptastic (and very briefly-appearing) Ceratosaurus in Jurassic Park III?”

    I was too pissed at the Incredible Spinosaurine Hulk to really pay much attention to the Ceratosaurus, but looking back, his extremely brief appearance in the film was a bit of a copout.

  8. #8 Raymond
    December 8, 2007

    “Sure, Ceratosaurus might have been a reasonable swimmer (its tail is deep and quite flexible), but there is little reason to take this seriously. Their argument mostly comes from the association of Ceratosaurus teeth with lungfish remains. Well, many terrestrial animals feed on fish an awful lot (perhaps even exclusively).”

    IIRC, Bakker et al. did a 15 year study of theropod teeth at several upper jurassic deposits.The ceratosaur teeth were near-exclusive with aquatic animal remains like crocs and turtle etc.While the allosaur teeth tended to be shedded mostly in drier regions.

    Has that study been rebutted?

  9. #9 Zach Miller
    December 8, 2007

    If you look real close at the JP3 Ceratosaurus, you can tell they just shrunk the T.rex model, gave it a different texture, and stuck a horn on its nose. Awful, awful model.

  10. #10 David Marjanovi?
    December 8, 2007

    Yesss!!! A wishbone on Ceratosaurus, and the coracoids almost touch! I already thought there was some law against mounting dinosaur skeletons the right way! :-) :-) :-)

    What I like about C. dentisulcatus is its diagnosis, as reported on the DML years ago: “Ceratosaurus dentisulcatus is one kickass big theropod.”

  11. #11 David Marjanovi?
    December 8, 2007

    To repeat myself: Yesss!!! This is the 5th most active ScienceBlog post at the moment! And that even though it’s 3 am over here and 2 am where you posted this. Congratulations! :-)

  12. #12 Nagi
    December 9, 2007

    “If you look real close at the JP3 Ceratosaurus, you can tell they just shrunk the T.rex model, gave it a different texture, and stuck a horn on its nose. Awful, awful model.”

    It’s even worse when you look at the little size chart that came with the DVD. They actually list Ceratosaurus as being as big as a T.rex.

    Of course, they also list Stegosaurus and Triceratops as being significantly larger than a T.rex, as well.

  13. #13 Darren Naish
    December 9, 2007

    Mike Keesey wrote…

    More accurately, coelophysoids are not ceratosaurs and dilophosaurids are not coelophysoids or ceratosaurs. Ceratosauria and Coelophysoidea are still monophyletic–they’re just non-overlapping and less inclusive than once was thought.

    Yeah, well said. I should have noted that I had the ‘traditional’ versions of these groups in mind: Ceratosauria sensu Gauthier (1986), and Coelophysoidea sensu Holtz (1994). For those interested, the deconstructions have mostly come from Carrano et al. (2002), Rauhut (2003), Yates (2005) and Smith et al. (2007), mostly*.

    * Sorry. Game over man.

    Refs – –

    Carrano, M. T., Sampson, S. D. & Forster, C. A. 2002. The osteology of Masiakasaurus knopfleri, a small abelisauroid (Dinosauria: Theropoda) from the Late Cretaceous of Madagascar. Journal of Vertebrate Paleontology 22, 510-534.

    Gauthier, J. 1986. Saurischian monophyly and the origin of birds. Memoirs of the California Academy of Science 8, 1-55.

    Holtz, T. R. 1994. The phylogenetic position of the Tyrannosauridae: implications for theropod systematics. Journal of Palaeontology 68, 1100-1117.

    Rauhut, O. W. M. 2003. The interrelationships and evolution of basal theropod dinosaurs. Special Papers in Palaeontology 69, 1-213.

    Smith, N. D., Makovicky, P. J. Hammer, W. R. & Currie, P. J. 2007. Osteology of Cryolophosaurus ellioti (Dinosauria: Theropoda) from the Early Jurassic of Antarctica and implications for early theropod evolution. Zoological Journal of the Linnean Society 151, 377-421.

    Yates, A. M. 2005. A new theropod dinosaur from the Early Jurassic of South Africa and its implications for the early evolution of theropods. Palaeontologica Africana 41, 105-122.

  14. #14 Darren Naish
    December 9, 2007

    David wrote….

    And that even though it’s 3 am over here and 2 am where you posted this.

    No, it was something like 3 in the afternoon when I posted it (Sb posts are published at Eastern time in the US, so the publication time on the article is just after 11 am: 5 hours prior). Believe me, at 3 am on a Saturday night I was not blogging! I was reviewing a paper :) Hold on, I’ve totally misunderstood.. you mean that it got into the top 5 at 2 am. Well, 2 am for me would have been 9 pm for eastern North America, so not an unreasonable time for lots of people to be online.

  15. #15 David Marjanovi?
    December 9, 2007

    No, no, what’s up is, apparently ~:-| , that I mistakenly assumed you had posted it shortly before I saw it. My capacity for logical thinking is negatively correlated to the time of night. Anyway, you are right in your last two sentences.

  16. #16 Warren Beattie
    December 9, 2007

    “One of my most favourite dinosaurs has always been Ceratosaurus…”

    Can’t argue with that. An unexpected but welcome entry! I’ll have to pay a visit to Glasgow sometime.

  17. #17 Thylacine
    December 9, 2007

    Awesome post! It astonishes me how much we still don’t know about these creatures.

    Maybe Ceratosaurus followed some kind of a Grizzly bear model.. fishing when they were running (or digging them out of the mud in the case of the lungfish) and catching smaller prey when there were no fish. OF course I wouldn’t go so far as to suppose it was an omnivore.

  18. #18 Jurek or Jerzy
    December 10, 2007

    Wouldn’t this horn hamper predatory behavior? Seems strange for me.

  19. #19 Tim Morris
    December 11, 2007

    KEELS ON IT”S TEETH?

    *coughVENOMOUScough*

  20. #20 David Marjanovi?
    December 11, 2007

    The keels are simply the cutting edges, aren’t they?

    Also, what would an animal with this kind of skull and teeth of such size need venom for?

  21. #21 Chris Glen
    December 11, 2007

    Have to agree – always been one of my favourites.
    Ceratosaurus was my choice when William Stout aked me what was my favourite dinosaur as he offered to sign a copy of the ‘New Dinosaurs’ with a sketch when I bought it off him at SVP2004 (to finally replace my old copy of the first edition that was destroyed by a classmate back in my school days).

    …and nice blog – keep up the good work!

  22. #22 Darren Naish
    December 11, 2007

    Thanks for the comment Chris. For those who don’t know, this is the same Chris Glen who (with M. B. Bennett) recently published a paper on foraging modes in Mesozoic birds and non-avian theropods in Current Biology. Nice paper. Just don’t talk about it with Dave Hone :)

  23. #23 DDeden
    December 24, 2007

    link
    says it had heavy solid bones, crocodile like tail, osteoderms.

    Perhaps it ambushed terrestrial animals at waterholes during drier periods, and aquatic ones during higher water levels? Many pictures show it running, but thick heavy bones aren’t typical for runners, more for slow (or ambush) waders. Horn and brow ridges protect from facial attack, I’d think.

  24. #24 David Marjanovi?
    December 25, 2007

    says it had heavy solid bones

    If so, that would be remarkable enough that I’d expect to have seen it mentioned in the primary, secondary, and tertiary literature. If only the at least quarternary literature mentions it, it’s probably wrong (…except that, not being a tetanuran, Ceratosaurus isn’t supposed to have camellate vertebrae).

    crocodile[-]like tail

    Just like any other non-avebrevicaudan dinosaur. Compared to most mammal tails, almost all tails look like that of a crocodile.

    osteoderms.

    Yes, two rows of small rounded osteoderms along its back.

    Simply ignore enchantedlearning.com. It is written for little children by people who don’t know a lot more than average little children.

    Horn and brow ridges protect from facial attack, I’d think.

    Nope. They only protect from attacks that come vertically from above and are stupid enough to target the snout. Considering the improbability of such attacks, we have to look for other explanations, such as sexual selection.

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