Tuesday, December 7, 2010

5 Questions for Tetsuto Miyashita

Well folks, you get two mini-interviews back to back this week! My friend and colleague Tetsuto Miyashita is a Masters student at the University of Alberta and recently published a new paper on a very interesting specimen of the tyrannosaurid dinosaur Daspletosaurus:

Miyashita T, Tanke DH, Currie PJ. 2010. Variation in premaxillary tooth count and a developmental abnormality in a tyrannosaurid dinosaur. Acta Palaeontologica Polonica 55: 635-643. APP is an open access journal, so you can download the article for free!

Tetsuto measures a little Tarbosaurus at the Paleontological Institute in Moscow.

1. What inspired you to conduct this study?

When I visited Tyrrell in 2007, my co-author Darren Tanke dropped a tyrannosaur premaxilla on my lap and quizzed me: "What's wrong with this specimen?" It's got only three tooth sockets, whereas almost all theropods, including all tyrannosaurids, have four. I started wondering what could mess up such a conservative trait.

2. Why is it important to consider development when studying fossils?

If you have two different species in front of you and wonder where the differences come from, you will find an answer in development. In other words, a sequence of evolutionary transformations are a history of modifications in developmental processes. Evidence is hard to find -- you can never visualize expression of genes in fossils. You rely on inferences, or simply speculate. But developmental interpretations based on morphology are arguably the most powerful voice in the narrative of evolution, because they explain how a diversity that we see in fossils and living forms was generated.

3. Did this particular individual have enormous teeth?

Yes. The tooth sockets are 25% larger than you expect for a normal tyrannosaurid. The teeth must have been larger accordingly. It is a trade off -- you reduce the number of teeth and create a space to accommodate larger teeth.

4. How do your findings affect using tooth count as a character in phylogenetic analyses?

Two parameters affect a tooth count: space in which teeth fit in and sizes of the teeth. So, rather than simply counting teeth (which is problematic for reasons below), why not measure variation in the two parameters? When you formulate a character simply on tooth count, you have to break up often continuous variation into a few discrete states. No matter how you break it up, justifying this is difficult. On top of that, when two factors are in play, it is more to the point to treat them separately.

5. Which is the better of the two Dinosaur Provincial Park tyrannosaurids, Gorgosaurus or Daspletosaurus?

Daspletosaurus: the rarer, the more massive, and the longer forgotten. But there is an indestructible Japanese cartoon character -- Gorgo 13. For the sake of Mr. Gorgo 13, I wish Gorgosaurus was more of a match for Daspletosaurus.

(Shamelessly stolen from Wikipedia.)

Thanks, Tetsuto! Now go find the matching premaxilla to that specimen so you can tell us all about asymmetry.

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