Monday, November 21, 2011

Water Launching Pterosaurs

This post is a cross-post from H2VP (again), but should be of interest to readers.

I gave two presentations at SVP this year, and the second (in the form of a poster) was on pterosaur water launch. Specifically, I presented a model that Jim Cunningham and I have worked out for a plausible water launch strategy in Anhanguera. If you want to see what this might have looked like, turn your cursors here to Mark Witton's website. The relevant illustration is on the far right.

I will not give too much detail on this presentation at the moment, as it is shortly bound for PLoS ONE. However, here are some of the highlights:

- A bipedal water launch model appears to fail for Anhanguera (and other pterosaurs), just as the bipedal model fails for their terrestrial launch.

- A quadrupedal water launch model, in which the wings are the primary mechanism used to free the animal from the surface and to push along the surface to reach launch velocity, seems to check out for all of the parameters we can currently estimate with any confidence.

- Anhanguerids probably took multiple hops across the water surface to launch, but our calculations suggest that most of the actual energy expenditure was spent escaping the surface tension.

- Our model makes testable predictions about comparative anatomy of pterosaurs, which is important when building these kinds of models from fluid theory. Our model predicts that water launching pterosaurs should have features such as: warped deltopectoral crests or dp crests with flared distal ends, enlarged scapulae, extreme disparity between forelimb and hindlimb lengths, and reinforced scapulo-notarial joints. We have a more extensive list of features that can be shared a later date, but the primary note here is that these predicted features do indeed seem to show up mostly in marine pterosaurs, and less so in terrestrial taxa, so there is a least a loose, pattern-matching form of validation that can be applied to our hypothesis.

We hope to have animations and a full paper out on the topic of pterosaur water launch in the near future (next few months) so stay tuned!