Friday, January 29, 2010

Feathered dinosaur developments

Recently, three papers have been published on the subject of feathered dinosaurs and the evolutionary origin of birds. In the first, Alexander et al. made a model of Microraptor to test its gliding capability. Microraptor is one of those weird four-winged feathered dinosaurs. The paper is interesting, but the videos are really fun to watch. What I'd like to know now is what advantage does four wings have over two? Or is it just another way to get from here to there?

In a paper published online in Nature, Zhang et al. looked at fossilized melanosomes in feathers of both birds and feathered dinosaurs. The headlines about this paper that I've seen are treating this as if Zhang et al. have resolved what color these critters were. The far more significant discovery is summarized in the abstract of their paper:
Here we report that melanosomes (colour-bearing organelles) are not only preserved in the pennaceous feathers of early birds, but also in an identical manner in integumentary filaments of non-avian dinosaurs, thus refuting recent claims that the filaments are partially decayed dermal collagen fibres.
These filamentous structures have been somewhat controversial, because they are not pennaceous feathers, the kind of flight feathers that birds have today. Zhang et al.'s evidence suggests that the filamentous structures are indeed varieties of feathers, and not some other kind of integumentary structure.

The last report, published in Science by Choiniere et al., is not about feathered dinosaurs specifically but a "Basal Alvarezsauroid Theropod" called Haplocheirus sollers. This fossil continues to extend the stratigraphic range of important maniraptoran dinosaurs (like Velociraptor), which further bolsters the case for their relationship to early birds like Archaeopteryx. They also did a whopper of a cladistic analysis, with 99 taxa and 421 characters!

What's a creationist to do with all of this? As I told one of my students, God likes feathered dinosaurs. (Kind of a cop out, I know, but it's the best I've got right now.) In any event, it's going to be hard to deny the existence of feathered dinosaurs when paleontologists keep discovering new ones. We need to get past denial and start making peace with the fact that feathers are not uniquely avian.

Alexander et al. 2010. Model tests of gliding with different hindwing configurations in the four-winged dromaeosaurid Microraptor gui. PNAS doi: 10.1073/pnas.0911852107.

Zhang et al. 2010. Fossilized melanosomes and the colour of Cretaceous dinosaurs and birds. Nature doi:10.1038/nature08740.

Choiniere et al. 2010. A Basal Alvarezsauroid Theropod from the Early Late Jurassic of Xinjiang, China. Science 327:571-574.