Are flightless birds a reversion?

no.i'm not the best person to ask, really, because i'm one of those people that holds the attitube of "just what the hell is a bird, anyways?" all birds, however, seem to decended from a single flying ancestor, something very much like archaeopteryx.it's interesting to note that flight seems to have, at the very least, been lost repeatedly by birds. possibly re-evolved. it's even quite possible that some dinosaurs we know and love (like velociraptor) evolved from ancestors that flew (archaeopteryx seems to be relatively close to the ancestral deinonychosaur). essentially modern birds were living in the cretaceous, and soon after the death of the dinosaurs, and until just two million years ago, we had giant terror birds running around filling essentially dinosaurian niches.oh, and i was going to make a separate thread about this later -- did you hear we've got another example of a cenozoic dinosaur? apparently, dinosaurs only died about sixty-FOUR million years ago, and seem to have survived the asteroid impact by about a million years.

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Do you know what the "old jaws" bit is about? Is there some basic morphological difference between the jaws of the two superorders?

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Most paleognaths have long necks and long legs, and are specialized for running rather than flight; indeed, the ratites are all completely flightless. The group is not separated because of this though, it is rather based on the form of the jaw.

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Thanks

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this might help:
(source)

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It appears that modern and ancient paleognaths have, or had, carpometacarpuses.Besides which, they and the neognaths are all neornithes together, so for their common ancestor to be flightless, something very odd must have happened.Edited by Dr Adequate, : No reason given.Edited by Dr Adequate, : No reason given.

Yeah, and another thing --- WHY ARE THERE STILL MONKEYS?!?!?Answer me that you Godless heathen. Edited by Adminnemooseus, : Off-topic banner.

I agree that the ratites (ostriches, emus, moa and their ilk) are unlikely to represent a lineage that "never developed flight". The ratites as a group represent a very small percentage of avian taxa that are flightless. Rails, for instance (family Rallidae, order Gruiformes) represent over two thirds of all known flightless birds. Since all of the flightless rails, as well as other flightless species (there are a number of pigeons, a wren, a comorant, etc) known have very close relations which retain the power of flight, it would be odd if the flightlessness of ratites represented a non-flying evolutionary lineage.Additionally, I prefer to consider secondary flightlessness an adaptation rather than a "loss of ability". Since the biological energy cost of powered flight is apparently quite high, it might be better to consider flightlessness a "plus" rather than a "loss" in those lineages whose genetic plasticity allows this adaptation. In other words, flightless rails can, at least in some sense, be considered more derived than their flighted predecessors.Hope this helps.Edited by Quetzal, : speling and clarity

because the development of a carpometacarpus so wonderfully recapitulates the evolutionary history of the bird, it's actually totally possible for some birds to simply re-develop claws and such thought neotonoy.i'm not sure about ratite claws. i've heard mixed information, and i'm no ornithologist. well, very odd things DID happen. the question is whether this is a plausibility. the answer in this case, however, is "no."

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i find it interesting that flightlessness is actually such an advantage that birds keep secondarily loosing flight.

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Hi arach,It makes sense when you think about it. Although there might be other reasons for secondary flightlessness, all (except African ratites - which I guess is why we're having this discussion) flightless birds evolved in locations where flight was no longer a survival benefit either from the predator standpoint (e.g., Genyornis or the phorusrhacoids from South America) or prey. If there ain't nothing eating you and you don't need to catch fleet prey, why bother? I see it as very similar to the loss of sight in cave-dwelling fish and inverts. Obviously I could be wrong, but from an ecological adaptation standpoint, anything that reduces your energy costs is a good thing...

well, that can't be entirely true. we never seem to see, for instance, warm blooded animals "reverting" to cold blooded. at least, none that i am personally aware of. yet, cold bloodedness is VASTLY superior in terms of energy usage. cold blooded animals simply do not need to catch and eat as much food, because they do not have to worry about keeping up body temperature with their metabolism.this is probably because no one particular advantage is weighed in a vacuum. it is the combination of factors and how they interact that matters most.

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okay, that's just really cool.

Here's a story from LiveScience about a new dino-bird called Mahakala. Flightless, but tiny and ready to go.

Remains of a petite dinosaur reveal that some of the ancestors of birds had already shrunk in size before flight evolved.

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The dinosaur, a mere 2 feet long (70 centimeters) and weighing the equivalent of two cans of soda, roamed the Earth 80 million years ago during the Cretaceous period (between 146 and 65 million years ago).

Tiny Dino Was Ready to Fly | Live Science(Yep. Just another in a long line of discoveries that creos insist no one has ever found.)
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ArcherAll species are transitional.

Absolutely. Moreover, when we're talking about adaptation, we have to consider the rather ambiguous concept of historical constraint. It would seem to me (although the dividing line is really tricky), that "losing" wings, for instance, is a lot easier than the major re-wiring that would be required in going from endothermic to ectothermic (or vice versa, for that matter).In addition, the evolution of flightlessness in the rails I mentioned, for instance, took place in anything from a few tens of thousands to at most 1-2 million years maximum (based on the age of the islands they inhabit). Mostly a lot less time probably. Major rewiring could be done, but not that fast. I'm not sure how long it took to develop full endothermy from putatively ectothermic amphibians, but I'd guess quite a while.