Theropod tooth morphology – some definitions

This is a subject I have been somewhat deliberately avoiding since it seemed a bit too technical and would involve me having to create some figures or do something more complex than just typing. However with an upcoming paper on teeth that I want to talk about on the blog it seems like I’ll have to do it sooner or later, and before is definitely more relevant than after. So in the best traditions of compromise / laziness, I’ve kept it as brief as possible.

I’ll be clear from the off that I’m only trying to cover the general features that turn up in theropod teeth and not describe the range or variation or which features appear in which taxa.  Even so, it’s worth noting that theropod teeth are fairly conservative and the general statement that they are laterally compressed, recurved and have serrations on the front and back edges covers most of them quite well. There is inevitably a quite a bit of deviation from this and some teeth are really quite diagnostic (like those of derived troodontids) while others are pretty generalised and hard to pin down in isolation (like those of basal tetanurans). Here then are the terms (as best as possible, since sadly they are not all standardised) that you’ll most commonly come across with descriptions of theropod teeth.

So obviously the bit at the bottom that sits in the jaw is the root and bit exposed on top (with the enamel covering) is the crown. So much so boring. Although the root is mostly missing (and the crown is broken too) you can see the junction between the root and crown as indicated by the blue arrow. This is usually indicated by a change in colour in the fossil and a slight constriction.

Most theropod teeth have a degree of recurvature, that is they curve back over themselves so that the tip of the tooth is closer to the rear than the front. Here I have marked the anterior face of the teeth with an orange arrow so you can see how they curve.

Also usually present are a pair of carinae, the sharp edges of the teeth. Obviously these are usually on the anterior and posterior edges in line with each other, but they can be offset from the centreline of the tooth or split in some cases.

Along the each carina there’s usually a series of serrations, or more properly, denticles. These are often absent (typically because they are not preserved or wore away) or highly modified and there’s quite a range of morphology if you look in detail. One carina is nicely raised up and clear here and you can make out (just) the individual denticles marked with a yellow arrow.

Theropod teeth can also have various degrees of ornamentation, most notably the wrinkled enamel effect, which is hard to describe accurately, but really quite self-evidence when you see it. Less common, but occasion, the tooth can be ornamented or fluted with various sub-parallel, vertically orientated striations.

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4 Responses to “Theropod tooth morphology – some definitions”

  1. 1 Mike Taylor 21/01/2010 at 9:40 am

    Wot no mesial/distal/labial/lingual?

    • 2 David Hone 21/01/2010 at 10:09 am

      Well I did say it was simple, and the lingual-labial bit was covered in the ‘directions’ post a while back (though I forgot to link to it here).

  1. 1 A Late Cretaceous, Asian, Baryonychine. Probably. « Dave Hone’s Archosaur Musings Trackback on 25/01/2010 at 7:52 am
  2. 2 Theropod teeth again « Dave Hone’s Archosaur Musings Trackback on 25/02/2010 at 7:52 am
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