Teeth like steak knives or bananas or well, tyrannosaur teeth

You can’t go too far talking about Tyrannosaurus without coming across one of two great statements, that they had teeth ‘like steak knives’ or teeth ‘the size of bananas’. These are both really, really annoying, in that they sort of convey semi-accurate information while at the same time being really, really misleading. I thought I’d take a little time today to bust these two with a swift one-two and leave at least one corner of the internet with a little less pseudo-information.


Let’s start with the size issue. I can see the concept behind this, a big banana is not so far removed from a big Tyrannosaurs rex tooth. The only trouble is that of course there are lots of smaller teeth in the jaws than just the biggest ones in the maxilla. And of course bananas vary enormously in size and length, so it’s not the greatest unit of size for scale. And of course if you *look* at a Tyrannosaurus tooth, (ooh, look what photos I happen to have, how handy) then things get a bit more complex. Even the biggest crown is not that long, so actually even a pretty small banana is probably bigger (well, longer, another issue of course) than the crown. And since that is really what we should be dealing with, it becomes rather pointless. Ironically the roots are so big that if you include them, then the tooth is huge and much bigger than even the biggest bananas that I have seen. So as a measure a banana is either too big OR too small at the *same* time. Impressive! And not really the same shape either. In short, please people, let’s stop using this as a description of tooth size for Tyrannosaurus.

And so to steak knives. First off, take a look at this:

While the two images above were in lingual and labial views, this is an anterior shot of the tooth. If you get something that fat and rounded handed to you by a waiter the next time you order a steak you but wonder if he wanted you to tenderise it rather than cut it up. The tooth is damned near circular in cross-section and about as far as you can get from a ‘knife’ if you tried (and indeed is less blade-like than any other theropod tooth). As we know, Tyrannosaurus had a bone-crunching bite, so what’s with the knife analogy?

I’m certain it dates to a paper by Abler where he examined the effects of the serrations on Tyrannosaurus teeth and concluded that the *way* in which they cut was most similar (at the microscopic level) to that of a steak knife. Note that this means that those tiny serrations on the teeth are cutting *like* the giant serrations of a steak knife. This doesn’t mean that they acted like one though. If I stuck that thing into your arm or chest with the power of a rex bite I rather suspect what would most impress on you (other than the need for extremely urgent medical attention) would be the massive and sub-circular puncture wound and not the nice little edge to it in a couple of places.

As such, again, please stop describing these as ‘like steak knives’, a small part of them does, superficially cut like a steak knife, but they are not shaped like them and don’t act like them and aren’t used like them.

25 Responses to “Teeth like steak knives or bananas or well, tyrannosaur teeth”


  1. 1 Mark Wildman 04/12/2011 at 12:12 pm

    Completely agree here Dave but suspect your plea for the use of better terminology will fall on deaf ears. Steak knives and bananas are here to stay unfortunately.

  2. 3 TB 04/12/2011 at 12:26 pm

    Not to mention bananas are very impractical to cut meat with… :P

  3. 4 Tim Donovan 04/12/2011 at 1:05 pm

    How ’bout railroad spikes? :)

  4. 6 Thomas R. Holtz, Jr. 04/12/2011 at 2:22 pm

    Railroad ties are another classic version. TB: that is part of the point: tyrannosaurid teeth CANNOT CUT. (Or at least, the anterior maxillary and dentary teeth cannot cut.)

    “Steak knife teeth” was used even when I was a kid, and may go back far earlier (like early 20th Century): an enterprising historian of popular science might be able to trace that one.

    P.S. After next week, I hope to start the next installment of Love the Tyrant, Not the Hype.

    • 7 David Hone 04/12/2011 at 2:45 pm

      Hi Tom, didn’t know it dated back that far, though I’m sure Abler’s (actually very good) paper helped popularise it, even if it didn’t start the trend.

      Great to hear more is coming my way!

  5. 8 Heinrich Mallison 04/12/2011 at 3:45 pm

    a timely post, saves me the bother of writing it myself, which would never have been as good as your work! :)

  6. 9 Robert A. Sloan 04/12/2011 at 4:09 pm

    I got both the steak knife and banana descriptions as a small child, so this article gave me a good laugh. Yep. That’s not something I’d want to dip in chocolate or carve up some prime rib with. Unless I was a T. rex, in which case I’d be getting a big chunk of the whole cow with that prime rib as only part of it.

    Very cool article, funny and informative with great photos. Now you’ve got me jonesing to have a fossil budget again. Ah, someday…

  7. 10 Zhen 04/12/2011 at 5:01 pm

    These banana steak knife descriptions are usually found in dinosaur books too. So either paleontologists or editors should take some of the blame.

    I personally don’t think they’re that bad and here’s why. This is from the view point of my childhood. These descriptions gave me something to help visualize that size and thickness of the tooth and how they compare with other theropod tooth. I think kids are smart enough to realize things still come in different sizes, so I never took that description as an absolute fact, but rather a generalization.

    Without something to visualize, a kid’s imagination just goes wild. When the T.rex still had that kangaroo pose, I used to think it was taller than a 2 story building before actually seeing it in a museum. I wasn’t impressed by a 30 foot Allosaurus either. I imagined it to be much bigger!

    I do agree the knife thing might be more misleading. More books need to empathize the bone crushing part.

    • 11 David Hone 04/12/2011 at 6:45 pm

      Whoever used a poor analogy / reference should take the blame. And maybe you understood that this was a generalisation, but many would not so I stand by my assertion that it causes more confusion than it brings clarity. The point is that you need to be clear – sure a banana gives a not unreasonable impression of the shape, but why not say “the crown is the size of a large banana” that gives so much better context than “the tooth is the size of a banana” one more word and one different word and it’s immediately so much closer.

      “The biggest crowns could be likened in size and shape to a big banana” is even better and just a few words more. Clarity and accuracy and a little wiggle room in just a dozen words or so, how hard can that be, and is it really hard for even a child to grasp? I don’t think so, so use it. Make it plain and put it in context.

      • 12 Zhen 04/12/2011 at 7:58 pm

        “but why not say “the crown is the size of a large banana” that gives so much better context than “the tooth is the size of a banana” one more word and one different word and it’s immediately so much closer.”

        Yes, that’s true. Most of it is just the root deeply buried inside the skull / jaw, and that’s makes up a bulk of the size, and not the part that sticks out.

        I forgot to ask, are those pictures casts or the real deal?

      • 13 David Hone 04/12/2011 at 8:09 pm

        It’s a cast. I can’t afford a real rex tooth.

      • 14 Zhen 04/12/2011 at 8:46 pm

        Still looks very nice. Much better than the embarrassingly poor cast available at the AMNH. It’s the one where they let people touch a full cast of the mandible along with the teeth.

  8. 15 Jaime A. Headden 04/12/2011 at 10:22 pm

    A lot of people are actually unaware that when seeing an isolated tooth, how much of that is actually exposed as a visible tooth. They may perceived that much, or most of the tooth is exposed and visible in the jaw. I avoided the “size” issue entirely when I made a strict reference to their “banana-ness” here and here, so while I helped perpetuate the “banana” comparison, I attempted at least to somewhat detract from it.

    This post (not mine), of course, does a better job of describing the whole shape of the tooth on a visual level than I did, and that’s good.

  9. 16 Jerry Hone 04/12/2011 at 11:30 pm

    I entirely understand the frustration that you as a scientist feel about the inaccuracy of the description, and especially as a family member I entirely sympathise with your need for detail correctness :) ! However, putting myself in the position of a small child trying to learn about dinosaurs, I can’t help thinking that the descriptions that you rail against are, in fact, reasonably OK for the man in the street (like me)! For a child to be told that “the crown is the size of a large banana” as you suggest would, I’m sure, create images of a T Rex in robes perching on a throne with very strange headgear! Maybe not so helpful, although a perfectly good description for a prehistoric dentist. Similarly, I think the steak knife analogy is simply indicating that you wouldn’t want to get in the way of the teeth!
    I do wonder if it was these sorts of descriptions in books that you read in your youth that triggered your imagination and set you on your current path.
    Great article, by the way – thoroughly enjoyed reading it!

    • 17 David Hone 05/12/2011 at 10:40 am

      Well I do get where you’re coming from Jerry and I’d also agree that there’s a difference between trying to get things across to say young children vs older and interested kids / adults. Sure if a 5 year old wants to know, then ‘bananas’ are probably the best you can do in one word. However, as noted in my exchange with Zhen, just the addition of a couple of qualifiers make it so much more accurate, even if I still generally dislike the term overall.

  10. 18 Matt 05/12/2011 at 12:18 am

    Well you just need to be more specific with your banana nomenclature. Are we talking Cavenedish Bananas?
    “Trex has teeth like Cavendish bananas!”
    Which sounds a little posh.
    Or for smaller teeth they could be described as being:
    “Teeth the size of Lady Finger Bananas” which sounds a little weird and possibly suggests a diet leaning toward the feminine only.
    Even stubbier teeth could be compared with Ducasse Bananas.
    Of course, for a more macho sounding comparison you could go with: “Vicious stabbing teeth like Red Dacca Bananas!”

  11. 19 Mark Robinson 05/12/2011 at 3:15 am

    Thanks for the article and pictures, Dave. They help to clarify things a bit. I can now see that T. rex teeth are exactly like chili peppers. Big black chili peppers. I wouldn’t mind betting that they taste hot, too.

  12. 20 Herman Diaz 05/12/2011 at 4:44 am

    How far back does “teeth like bananas” go? The 1st time remember seeing T.rex teeth compared to bananas was the American version of WWD.

  13. 22 Tim Donovan 05/12/2011 at 12:53 pm

    It was Bakker who compared them to railroad spikes. “Teeth like bananas” may have originated with Horner and Lessem perhaps(?)

  14. 23 Your Name's not Bruce? 05/12/2011 at 5:29 pm

    “What about pointed sticks?”


  1. 1 A little more on teeth « Dave Hone's Archosaur Musings Trackback on 11/12/2011 at 8:39 am

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