The tyrannosaur overbite

Many thanks to Darren Tanke today for loaning me this photograph of a Gorgosaurus, one of a number of tyrannosaurs from the Late Cretaceous of North America. This is a great photo as it really shows off one outstanding feature of tyrannosaurs (and indeed theropods in general) namely the fact that the teeth and jaws of these animals do not meet together as they do for humans (and other mammals, and lots of other things). Instead, the  lower jaw slots inside the upper one so that the teeth move past each other rather than coming together.

GorgoHowever you almost never see this. In mounted skeletons the jaws are inevitably open to give a dramatic gape and this is mimicked in a huge amount of palaeoartworks. Even in scientific drawings the jaw is typically half open to show the anatomy of the mandible, or missing entirely. As a result, this is very rarely illustrated and thus I imagine appreciated by many people. So here you have it, the tyrannosaur overbite, with the teeth of the upper jaw being clearly visible as they overlie the mandible. Incidentally this is not an extreme version, I know of (but sadly have not seen) a Ceratosaurus where the teeth in the upper jaw are so long that they finish below the bottom edge of the mandible when the jaws are shut! Toothy.

 

 

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12 Responses to “The tyrannosaur overbite”


  1. 1 Thomas R. Holtz, Jr. 28/10/2009 at 8:57 pm

    I refer to this as the “wrap-around overbite”.

    • 2 David Hone 28/10/2009 at 10:55 pm

      This is something I think we could actually do with a technical term for since it arises before theropods evolve and then disappears later on (birds and oviraptorosaurs) so is a character that changes, yet is important and diagnostic. And accurate though your term is Tom, I’m not sure it does the job.

      Not, I should add that I think this is the place for people to suggest alternates, I merely think that soemthing formal would be useful for describing theropods crania and the evolution of this feature.

      • 3 Tor Bertin 29/10/2009 at 4:27 am

        Truth be told, I’m surprised that any descriptive terminology hasn’t come about… is it due to an overall lack of dealing with the feature in various studies, or have people only mentioned it in an informal sense?

      • 4 David Hone 29/10/2009 at 8:39 am

        I think it rarely gets mentioned to be honest as it’s one of those things that everyone ‘knows’ and so never mentions, despite the fact that there may well be some additional useful information in exactly how these fit together.

  2. 5 Tor Bertin 29/10/2009 at 4:17 am

    Lateral dental-mandibular juxtaposition!

    All right, maybe something less wordy… ;-)

  3. 6 Tor Bertin 29/10/2009 at 4:20 am

    Additionally, though I knew it existed, the contrast in that photo is pretty striking. Self-paleontological training is far harder when you have very limited access to actual fossil specimens (aside from a few vertebrae and fractured teeth, the closest accessible collection is roughly 250 from campus, so as you can imagine visits are infrequent!), so photos like this are very cool.

  4. 8 Dan Varner 29/10/2009 at 10:20 am

    The second, more distant, figure of Tyrannosaurus in Knight’s famous Field Museum mural shows the overbite as well as does a bronze of rex he did at about the same time. What’s really puzzling to me is that Cope did a restoration of “Laelaps” in the 1860’s showing the overbite. The restored head is so tyrannosaur-like it’s almost creepy. The figure is reproduced in Jane Davidson’s _The Bone Sharp_, her biography of Cope. I have a scan of the drawing if someone wishes to post it or just have a peek.

  5. 9 David 01/11/2009 at 11:42 pm

    Is this different from a crocodile’s teeth positions? (Just spent the weekend seeing a lot of saltwater crocodiles in Kakadu National Park).

    • 10 David Hone 02/11/2009 at 8:46 am

      Certainly. In the theropod overbite, each and every tooth from the upper jaw overhangs the lower, and not one of the lower jaw teeth are visible. In a croc, some of the upper teeth overlap, but not all, and some of the lower teeth can protrude over the upper jaw.

      As a result the pattern is very different (and it varies between different crocodile species too) and the biting effect is rather different with teeth coming together somewhat in crocs, while sliding past each other in theropods.


  1. 1 Gorgeous Gorgosaurus « Dave Hone’s Archosaur Musings Trackback on 17/05/2010 at 9:26 am
  2. 2 Special Guest Post series coming soon « Dave Hone's Archosaur Musings Trackback on 23/10/2010 at 7:52 am

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