Posts Tagged 'flight'

What a b*stard!


OK, so that’s a shocking title, sorry but what else could I do? For those who don’t know, this is a Great Bustard (Otis tarda) which, depending on quite which source you cite, is the heaviest flying bird. Most people concentrate on Andean condors or wandering albatrosses when it comes to the size of flying animals, but if anything getting into the air with more weight as opposed to bigger wings is more of an achievement. Between the three we can potentially learn a lot about locomotion in heavy flying animals (which of course has direct relevance to pterosaurs) yet while it’s understandable that little has been done on the others given the difficulty of keeping them in captivity, it’s odd that so little has been done on the bustard. This one was snapped in the Beijing Zoo and thus was very accommodating, though now they have been successfully reintroduced to the UK I hope to see them wild in my homeland one day.

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Birds of a (leg) feather

I’ve commented on the Musings before about the presence of feathers on the legs of Archaeopteryx an important aspect of their anatomy that had gone largely overlooked (or at least unremaked upon) for far too long and of course is more interesting in the light of fossils like the ‘four-winged’ Microraptor. While the idea that flight might have evolved from a four-winged stage (via elongate leg feathers to provide the extra wings) is interesting, one wonders why before Microraptor it had garnered so little attention. I’m referring really to birds like this vulture:
The elongate feathers on the leg are really pretty obvious here and indeed to anyone who ahs ever watched them fly, or other big birds of prey like eagles and buzzards the same thing is clear (especially when striking or coming in to land) – some birds have very Archaeopteryx like feathers on their legs. The question I would pose is just why were feathered legs on Archaeopteryx such a surprise, or for that matter those of Microraptor or Anchiornis? Anyone looking at a decent range of birds would see a clade that had very similar feathers clearly using them in an aerodynamically useful way (if largely to steer or break rather than to generate lift). It’s not hard to see that maybe an early bird or proto-bird still struggling to generate sufficient lift or power (or for that matter steering) might have benefited from an additional source of control and breaking. People have blindspots and before anyone asks, no I have not dug through the last 150 years of flight research to check how often four winged dinosaurs / leg feathers / control during the origin of flight were mentioned or expounded upon, but I would argue that: a) most people were surprised by the appearance of Microraptor / Archaeopteryx legs feathers (including a large number of specialists) and b) they really should not have been given that plenty of birds have and use them. As echoed recently in the SV-POW posts on necks, why do palaeontologists insist on working only on fossils when we have living animals to compare them to?

Note: I know the feathers themselves are quite different between living and extinct taxa are different and may not have been used in even vaguely similar ways, my point is that we can see birds do things with leg feathers now, so why was the possibility of leg feathers in the early evolution of birds ignored?

A pelvis at the front – the notarium

Time to continue the general lesson in odd bits of pterosaurian anatomy and here we have a real specialisation: the notarium. This is unique to larger pterodactyloids and is essentially a fusion of the vertebrae that make up the spine where the shoulder articulates with the back to produce something that looks rather like a pelvis at the front. It has some interesting connotations for pterosaur evolution and ecology, and that of the development of bone in general.
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Guest post: How did pterosaurs extend their wing finger?

edina-daveThere are all kinds of aspects of palaeontology that in some ways we can only guess at how these things might have lived, functioned and behaved as living organisms. However one of the key aspects of science is the ability to make predictions and with careful use of analogy and homology (and of course the fossil record), we can try to work out some of those complexities that otherwise might leave us stumped. My former student Edina Prondvai and I have a new paper coming out in Historical Biology discussing how pterosaurs might have been able to extend that massive fourth finger and keep it stead during flight while minimizing energy expenditure. Edina takes us through it in this guest post:

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Into the air!

Mike Habib (right) with Musings favourite Luis Rey

Mike Habib (right) with Musings favourite Luis Rey

This time out, say hello to Mike Habib‘s work on quadrupedal launching. Just how did those giant pterosaurs get into the air?

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This time out we move onto extant archosaurs and the question of why would some birds lose the power of flight?

As ever the answers are available here. This is a good illustaration of a few points on evolution however – birds went to quite a lot of trouble to evolve flight (so to speak) so why was it lost (really quite often – ostriches, kiwi, great auk, penguins, dodo, kakapo, Sephen’s Island wren among plenty of others)? Flight is of course just one component of bird life and bahaviour, and its evolution and maintenence is a huge energetic cost which between them can provoke a variety of situations under which flight may be lost.

Pterosaur wings 2: structure

Ok, so following on from part one now we have a ‘broad’ wing with an expanded tip – now to the nitty gritty. The pterosaur wing (as I have previously stressed) is not some sheet of tough leather, but an incredibly complex organ which in many ways is actually quite superior to the equivalent structure in bats (all this ‘pterosaurs as bad fliers’ junk can go too) and would have allowed them superb control over their wings during flight. The pterosaur wing is made up of at least 5 layers and probably more. It is hard to tell as obviously looking at this kind of microstrucutre is pretty difficult and we have to rely on comparing some very different fossils, preserved in very different ways for our information. In addition to an outer epidermis (top and bottom), there are three key features that we do know in quite good detail though and these are worth spending some time over. Some of these might be duplicated (i.e. there could be two muscle layers) and so five is a conservative figure as there could be more, or other layers might interact and be less clear-cut than we think.
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Pterosaur wings 1: shape

Flight is inherently really interesting and really complicated, especially for a flying animal where a single pair of wings have to produce all the necessary thrust *and* lift while also providing most of the steering. It is something humans have singularly failed to come even close to matching with machinery, yet pterosaurs were flying from at least 230 million years ago. For some reason people (and here I can include some researchers who should know far better) seem quite happy to assume that pterosaurs were that great in the air and just sort of glided about on some inferior proto-bat-wings. Oddly enough, I really don’t agree with that interpretation and I will hope to justify that a little here.
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