Slanted Science

Published online today in the journal Proceedings of The Royal Society B (Biological Sciences), is a paper which describes fossils of a new kind of flying dinosaur, or pterosaur.
Chronologically, the creature falls between two known stepping stones of pterosaur evolution.
Morphologically, however, the fossils are somewhat surprising, and seem to provide evidence to support the ‘Modular Evolution‘ theory.

Pterosaurs thus far discovered have had one of two body plans: the more ancient type, which were small-bodied, with relatively long tails; or the younger (more advanced) type, which were bigger and had relatively short tails.

Scientists expected that the fossil gap, if it were ever filled, would be populated with pterosaurs displaying intermediate characteristics (gradually shortening their tails and increasing their body size). However, this paper describes the first of these transitional species to be found, and the results are surprising.

Informally called ‘Darwinopterus’ (sidenote: can we please stop it with naming everything after Charlie? I’m getting pretty sick of all these damn Darwin species names. Get creative, guys: how about Pterosaurus Slanticus? You with me?), this fossil shows a body plan split in two between the ancestor and descendant forms.

So, Pterosaurus Slanticus has a small lower body, with a long tail attached (like its ancestors). But it also has a flexible neck and massive head with sharp teeth, like its descendants. This has evolutionary biologists all excited (don’t forget, these are people who get energized by the prospect of spending three months on a mountainside in Chile, using a tiny brush to pull a fragment of dinosaur’s toenail from the ground).

What Pterosaurus Slanticus shows is perhaps the first evidence of modular evolution, where certain body compartments evolve at an accelerated rate, while others lag behind. In this case, the head and neck have advanced, to produce more efficient killing apparatus, while the lower body has remained in the ancestral state.

One idea might be that, at that time and in that environment, small changes in the body’s killing module (jaws, teeth) conferred much greater survival advantages than similar, small changes in the ground-walking modules (tail length, leg/pelvis arrangement). Furthermore, the concept of modular evolution is tied in with evolutionary biology’s old favorite, the Hox gene family. The authors state:

“‘The phenotypic modules identified here match closely to the expression domains of Hox genes … This raises the possibility of a link between module selection and genetics and suggests a promising avenue for further exploration.”

So, hooray for another transitional fossil to grind into the face of creationists and other crazy folk. And some interesting ideas to follow up.

Don’t Hold Your Breath, But This May Lead To: Linking Hox genes with gross evolutionary changes opens up the possibility that, rather than just ‘texter’s thumb‘, the offspring of today’s kids may actually start developing a whole new hand structure, the better to cradle and manipulate their iPhones with.