Friday, 14 May 2010

Pterosaur Sex

I recently was shown some porn in which a woman was having sex with three pterodactyls. As pterodactyls are extinct, they were of course men in costumes. They even flapped. This post is not about that, sorry to get your hopes up. Today I attended a guest lecture by David Unwin, one of the world's premier pterosaur experts, from Leicester University. I would love to give a run through of everything he talked about, but I do not have his knowledge and did not take any notes; everything I write here is from memory and will be a brief summation (with chunks potentially missing).

Until recently not much was known about sex in pterosaurs, or their ontogeny. Everything was speculation, a lot still is, and many of their habits were simply taken from birds. The media tended to portray pterosaurs as having nests which they return to and feed assorted live food to the young. A lot has changed since then.

Pterosaurs have been found to be sexually dimorphic, meaning the male and female have different appearances. This is very common, particularly among birds, but demonstrating it is not always easy. A variety of crest forms are found on pterosaurs, even among the same species, which supports the idea of sexual dimorphism. They were also used for display, which is suggested by the fact that there are a range of crest morphologies; natural selection would lead to more consistency. The clincher for sexual dimorphism came with the analysis of the pelvis, as the female had a larger opening for the egg to come out of, unsurprisingly they had shorter crests.

Until 2004 it was not actually known whether pterosaurs laid eggs or whether they were viviparous. In that year 3 embryo fossils were found. They were all contained in eggs, confirming oviparity for pterosaurs, but what is most interesting is their structure. Pterosaur eggs had soft shells, not the hard shells we are more familiar with from birds and dinosaurs. They also appear to have had some hard parts, but not many. This suggests that they did not incubate their young but instead buried them in the ground where they could absorb water. This is a useful trade off, as pterosaurs needed to be very light in order to fly.

The embryos also showed that pterosaurs emerge almost as fully formed pterosaurs, albeit smaller and not sexually mature. The ratios of their wingspan to other body parts fall in the range of fully grown pterosaurs and suggest that they could fly soon after they hatched. Analyses of pterosaurs at various stages of development also show that they grew slowly and possibly never stopped growing, though it did slow down in later life.

Well, that is all I remember. It was a good guest lecture and it seems I absorbed a decent amount of it.

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