Thursday, 28 July 2011

Some Musings On the Archaeopteryx Flight Conundrum

A reconstruction of Archaeopteryx
When Archaeopteryx was discovered in 1861, its position as a reptile or a bird was uncertain. By 1990, its position as the first bird was largely unchallenged. Yet the recent discovery of Xiaotingia, a dinosaur with very similar characteristics to Archaeopteryx, has provided moderate evidence that its taxonomic placement might be wrong. Xu Xing, the palaeontologist who discovered Xiaotingia, said that its classification had been an unfortunate combination of excitement at the time and a lack of similar fossils for comparison.

Evidence for this theory includes Xiaotingia's lifestyle and its morphology in relation to its taxonomy. I wondered whether feeding habits would support this theory. I realized that they could shed light on the ongoing debate as to whether Archaeopteryx was capable of powered flight or was simply a glider.

If Archaeopteryx was an avian, it would have been warm blooded and, because of the dangerous nature of the Jurassic forests where it made its home, would have possessed powered flight. A flightless, ground dwelling lifestyle would not have been viable. Powered flight, however, is physically very taxing. Its warm blooded nature would have meant that feeding would have been central to its lifestyle. While its teeth were probably evolutionary remnants.

Its size meant that it would not have been able to feed upon anything larger than insects, and would not have provided enough nutrition for a creature such as Archaeopteryx, making powered flight impossible. We have already seen that a flightless existence would not have been possible either. Its size meant that without powered flight, feeding would have been very difficult, casting doubt as to whether Archaeopteryx was warm blooded. This all lines up with Xu Xing's theory.

Now let us assume that Archaeopteryx was, in fact, a reptile. It would have been cold-blooded. Its size, however would have meant that it would not have lived close to the ground, within the reach of predators. It would have lived high up in the trees and therefore would have needed a means of moving around. As it was cold-blooded, powered flight would not have been possible.

The only viable way of getting around was by using its feathered forearms as a means to glide on air currents. Gliding requires very little energy. This combined with its cold blooded nature meant that Archaeopteryx  would have needed very little energy to survive. Its size still suggests that insects would have been the only obtainable prey. However they would have provided enough nutrition to allow Archaeopteryx to survive. Conversely, the typical morphological characteristics and lifestyle of birds would not enable Archaeopteryx to survive.

Xu Xing's theory has several salient points. If we apply these to flight versus powered flight, the evidence provided here shows that it is likely that this creature was a glider than a true creature of the skies. The blog post presented here is merely a theory about the Archaeopteryx conundrum rather than a solution to.