Thursday, April 09, 2009
Troodon formosus in Alaska
Alaska's theropod dinosaurs have, until now, been known only from dental remains. Shed teeth, that is. No bones attached to said teeth, unfortunately. Our theropods (Dromaeosaurus, Troodon, Gorgosaurus, and Saurornitholestes) are all known from other places (Alberta, Montana), too. There's not a whole lot that sets Alaska's dinosaur fauna apart, aside from their unique living conditions. Interestingly, Troodon teeth are generally larger in Alaska than other spots, suggesting that our big-brained deinonychosaur was bigger. But is it a new species?
A paper published in this month's Journal of Vertebrate Paleontology describes two partial Troodon braincases from the Prince Creek Formation on the North Slope of Alaska. These two cranial bits represent the first non-dental remains of a theropod dinosaur in my state. Braincase fragments aren't a whole lot to get excited about in and of themselves, but they are diagnostic enough to solidify the idea--previously based on dental evidence only--that Alaska's troodontid is Troodon formosus. But more interestingly, the paper points out that Troodon teeth in Alaska are larger than Troodon teeth in Alberta and Montana, and the authors suggest that the increase in body size is a response to the "extreme light regime" of Alaska's North Slope. What's more, the fact that braincase fragments were found at all from Troodon, along with the large number of isolated teeth, implies that Troodon was the most common theropod dinosaur in Alaska at the time. Perhaps its large eyes helped it to survive the dark periods of the winter.
This, coupled with its feather coat, endothermic metabolism and smarter-than-the-average-theropod brain, probably meant that Troodon wintered in Alaska. Whether any of our dinosaurs migrated is up for debate--I imagine the larger herbivorous dinosaurs took advantage of warmer climates in the winter. and the bigger theropods (like Gorgosaurus) may have followed them down. But it looks like Troodon was a permenant resident, which is kind of cool. Now let's cross our fingers for more Alaska material getting published!