Some extracts from the latest   www.sciencedaily.com/

Picture Credit: H. Tischlinger

Paleontologists of Ludwig-Maximilians-Universitaet (LMU) in Munich are currently studying a new specimen of Archaeopteryx, which reveals previously unknown features of the plumage. The initial findings shed light on the original function of feathers and their recruitment for flight.

. . .  The eleventh specimen of the iconic "basal bird" so far discovered turns out to have the best preserved plumage of all, permitting detailed comparisons to be made with other feathered dinosaurs. . . . The new data make a significant contribution to the ongoing debate over the evolution of feathers and its relationship to avian flight. 

"For the first time, it has become possible to examine the detailed structure of the feathers on the body, the tail and, above all, on the legs," says Oliver Rauhut. . . . "Comparisons with other feathered predatory dinosaurs indicate that the plumage in the different regions of the body varied widely between these species. That suggests that primordial feathers did not evolve in connection with flight-related roles, but originated in other functional contexts," says Dr. Christian Foth of LMU and the Bavarian State Collection for Paleontology and Geology in Munich, first author on the new paper.

Predatory dinosaurs (theropods) with body plumage are now known to predate Archaeopteryx, and their feathers probably provided thermal insulation. Advanced species of predatory dinosaurs and primitive birds with feathered forelimbs may have used them as balance organs when running, like ostriches do today. Moreover, feathers could have served useful functions in brooding, camouflage and display. 

. . . These observations imply that feathers acquired their aerodynamic functions secondarily: Once feathers had been invented, they could be co-opted for flight. "It is even possible that the ability to fly evolved more than once within the theropods," says Rauhut. "Since the feathers were already present, different groups of predatory dinosaurs and their descendants, the birds, could have exploited these structures in different ways." The new results also contradict the theory that powered avian flight evolved from earlier four-winged species that were able to glide.

Archaeopteryx represents a transitional form between reptiles and birds and is the best-known, and possibly the earliest, bird fossil. It proves that modern birds are directly descended from predatory dinosaurs, and are themselves essentially modern-day dinosaurs. . . . 

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Replies to This Discussion

Well there were pterodactyls. 

Weren't those reptiles?  I've gotten the impression from ... somewhere that I'm totally blanking on ... that most, if not all, of what we think of as flying dinosaurs were really just flying reptiles and were not in any way part of the clade of reptile-descendants that we identify as dinosaurs, which later evolved into birds.

I'll have to do some research on this.

Good point about pterodactyls.  I have read so much about dinosaurs being feathered, I don't know which ones were, and which ones were not.  Must have been an interesting sight, with or without feathers.

Joseph P, also an interesting point.  You are more educated about dinosaurs than I am!

There are some gliding modern reptiles, including a snake:

John, it seems to me that a complete surface-texture change, adding feathers as covering for a large part of the body, would be a greater change than adding flying structures.  Feathers would be the greater structural change to evolve out of ... whichever structure they came through.  Wings just require a slightly different configuration of the skin over an existing bone structure and a slight reconfiguration of joints.

Think of flying squirrels and sugar gliders.  Your statement about vulnerability to predators doesn't ring true to me.  Those little guys get around just fine on the ground, with only a slight chance of snagging the loose skin on something, and even then probably not to the detriment of the animal.

I don't see why birds couldn't have come through a similar path, developing from arboreal species of dinosaurs which developed delayed-falling surfaces, which later evolved into gliding surfaces, then flying surfaces.  The two earlier stages wouldn't necessarily cause a particular vulnerability on the ground, and in the final conversion over to true flying surfaces, ground vulnerability wouldn't matter, since the animals would almost never spend any time on the ground, unless they missed a tree during a glide.

Adding feathers from nothing, after full flight had taken hold, would be much more dramatic than the other way around.  Reconfiguration of existing feathers, to make them more useful for flight, seems more the way of it.

Or, to look at it another way, you have two possibilities: parallel evolution of feathers or parallel evolution of flight.  Which seems more probable, given what I said above?  Feathers are a specific solution to a single problem: keeping warm.  Flight is the only solution for macro-organisms to get off the ground, and wings seem to be the way for organisms to do it.

The small number of creatures that have developed chemical rockets don't use them for sustained flight.

I want to see those creatures that have chemical rockets.

Are the wings of flying insects all descended from a common origin? 

Creatures that fly in the air - as opposed to "flight" in the oceans-

Flying fish?  modified fins or skin flaps?

Reptiles - apparently only ancient - modified limbs and skin

Mammals - bats.  gliders like squirrels.- modified skin, and modified limbs at least for bats.

Birds of course.  modified limbs, and feather.

Insects - specialized wing structures.

In the oceans, I imagine there are more modifications for actions that are similar to flying, but below water.

I too want to see those creatures that have chemical rockets.  Real life "Ass Blasters"? Never heard of them, and can't find any with google, except for:

I believe flying fish just have over-sized, specialized fins.

I'm not sure about insects.  With the wide variety of flying insects in a number of clades, I imagine there had to be at least some instances of parallel evolution going on.  That's a guess, though.  I haven't looked much into the evolution of insect flight.

Hi Joe – Just to address some of your thoughts – Per your post:

Think of flying squirrels and sugar gliders.  Your statement about vulnerability to predators doesn't ring true to me.  Those little guys get around just fine on the ground, with only a slight chance of snagging the loose skin on something, and even then probably not to the detriment of the animal.

I don't see why birds couldn't have come through a similar path, developing from arboreal species of dinosaurs which developed delayed-falling surfaces, which later evolved into gliding surfaces, then flying surfaces.  The two earlier stages wouldn't necessarily cause a particular vulnerability on the ground, and in the final conversion over to true flying surfaces, ground vulnerability wouldn't matter, since the animals would almost never spend any time on the ground, unless they missed a tree during a glide.

This is exactly what I said Joe. Per my post:

…. Evolution from gliding to flying is logical (would supplement survival techniques without imposing consequences) and feathers might have been selected after flight to improve the ability to fly…. development of feathers for purposes other than flying without a gliding period thereafter would have left the species for an extended period clumsily trading off one type of front limb usage (legs) for another (wings) with little or no associated natural advantages in the interim. The species would have of course been more vulnerable to predators during this time. Accordingly, it seems likely that if feathers developed before flight there was a pre-flight evolutionary gliding period all the same.

In other words I said that the development to flight from non-flight almost certainly required an interim evolutionary gliding period regardless of where in the progression that feathers might have developed.

My statement about vulnerability to predators involved, for the sake of discussion, the supposition that there was no interim evolutionary gliding period between non-flight and flight. Basically, I said that without such a gliding period the transition from non-flight to flight would have left the species, for all intents and purposes, crippled for an extended period of time as its front legs slowly transformed into wings without affording compensating natural advantages. This would have made it more vulnerable to predators for much of the transformation period.

As to when feathers developed, so far as we know now, flying animals that have them seem to have acquired them before developing the ability to fly.  However, I don't think there is anything about evolution that would preclude the development of feathers on non-feathered animals that already had the ability to fly. 

Again, I think we are both saying the same thing.

I guess I read a bit more speculation into your statements than you were actually engaging in, then.  Hmm.  Either way, I got that you were pondering the possibilities, rather than making any declaration about feathers forming on already-flying animals.

I was just indicating my stance of coming down heavily on the side of feathers-then-flight, plus giving an example about why I didn't find the predator vulnerability issue to be much of a consideration, for me, feathers or no.  I was mostly addressing stuff after the bit you re-posted here, and I did a very poor job of indicating points of reference.  No worries.

I probably should have spelled it out more in the first place.

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