Feathers, quills and mesozoic thrills

[amargasaurus cazaui]

  Okay so the title is a bit flashy. I wanted to set off a discussion about feathers, and quills. I am not sure I ever correctly understand the debate itself well enough to pose the central theme or question. What I wish to see and understand is the varied views on why so many dinosaurs are suggested as having feathers..the fossil evidence and papers that establish it. I know in China they are finding feathered dinosaurs at an astonishing rate. I am not attempting to debunk feathered dinosaurs in this thread, what I am seeking is input why they seem to occurr or are found in China and not so much the North American area. Of if they are being found here, again what is the fossil evidence? What purpose is suggested for animals like tianyulong and psittacosaurus to have quills? Are feathers and quills related in these species? Could feathered dinosaurs be a characteristic of a cooler climate, and perhaps here in North America they were not so likely due to a warmer more temperate climate? What dinosaur families do we have evidence for here as feathered? Purposes the feathers might have served? Is it likely that birds evolved first, and ultimately one line of bird became what we now understand are the maniraptors and velocitaptor families? 
  I will state up front on this topic, I have no viewpoints and really do not understand the various facts and points in the issue so I am looking for input and information, and not an argument. Thoughts? Ideas?
I know there seem to be a few camps in this debate, and I am not trying to provoke a fight or prove any viewpoint, more a desire to learn here.

[Patrx]

Ah, splendid idea for a topic, Amarga! You knew I was gonna chime in, of course  While I am definitely pro-feathers, I'm also no palaeontologist, so it'll be neat to read where this discussion goes. My understanding is that feather fossils are found in some places more than others mostly for geological reasons - the composition of  fossil sites and the nature of the animals' preservation is conducive to feather imprints in certain places, hence the abundance of feathered dinosaur remains in spots like Liaoning - and the rarity of direct feather preservation elsewhere.

As to their purpose, that I am less informed on. From what I know, it's not likely that feathers primarily evolved for flight to start with. It seems like it's just the one group of dinosaurs (birds) that have used them that way, and in the rest of the dinosaurs used them for display or similar. That makes sense to me, since dinosaurs have excellent vision and often use complex colors and patterns to communicate. Some dinosaurs, like dromaeosaurs, appear to have used their wings for stabilization, while running or during predation via the RPR model.

Regarding the correlation between feather distribution and climate; I'd be surprised if there's much of one. Generally, feathers aren't like fur - they don't trap heat the same way, they're more versatile. A bird can use its feathers to trap heat or to lose it, depending on how it positions them. So, big, feathery dinosaurs in hot climates make plenty of sense to me. The fact that feathers have been found not only on coelosaurs, but on the megalosaur Sciurumimus leads me to suspect that feathers are a trait of (at least) theropods in general.

Quills, I must say, I don't know much about. Are they basically like bare feather shafts? What might they have been for? On Psittacosaurus, where they everywhere on the body and just managed to be preserved on the tail, or where they just on the tail? No idea, honestly. Which dinosaurs had them? My suspicion is that they're pretty widespread, but rarely preserved, much like feathers.

Hypothetically, I suspect that if we'd somehow found fossils like Yutyrannusand Velociraptor first, instead of the likes of Iguanodon and Megalosaurus, feathery integument would be the default in dinosaur reconstructions, and us dinosaur fans would be contemplating how weird, say, Carnotaurus would look with nothing but scales on it.

[amargasaurus cazaui]

And how very appropriate you were the first to comment in the thread Pixel, I had this thread in mind when i made the comment earlier about koolasuchus . As I stated I am not much an expert on the topic at hand and wish , like yourself to let others throw out the valid points, so I will only comment on a few things here that I do somewhat have understanding about or at least a valid observation.
  I had read the reverse suggestion for evolution of feathers in at least one place, that they first began as downy smaller insulating type covering, rather than for flight. What evidence is there for or against one way or the other there?
  This somewhat touches on my previous comment, but I was considering some paintings of baby hadrosaurs and perhaps dromeosaurs, covered with tiny downy feathers when I made the heat related comment. It has been suggested dinosaurs had downy feather covering until they were large enough to internally self regulate their temperatures. If indeed those downy feathers were for heat preservation, that would suggest something similar could be linked to environment or location....or no?
Quills, function unknown. I suggest they might have made a great display feature...being kept nominally flattened but when angered or threatened flared up much like a puffball. It is hard to know wether they covered all of the body or just the tail as preserved, however Tianyulong did have them everywhere seemingly.

[Patrx]

And how very appropriate you were the first to comment in the thread Pixel, I had this thread in mind when i made the comment earlier about koolasuchus .

Hah. It seems I have garnered some sort of reputation as a fan of feathers 

As I stated I am not much an expert on the topic at hand and wish , like yourself to let others throw out the valid points, so I will only comment on a few things here that I do somewhat have understanding about or at least a valid observation.

Indeed. This topic can be a bit touchy for some, I suppose; so let's hope the discussion remains levelheaded and civil.

  I had read the reverse suggestion for evolution of feathers in at least one place, that they first began as downy smaller insulating type covering, rather than for flight. What evidence is there for or against one way or the other there?

Yeah, as I mentioned, it seems like flight is just one of many uses for feathers, and not the one for which the initially began to appear. The simpler, fuzzy feathers, do appear to be more basal, but  dinosaurs as early as Archaeopteryx had fully formed, vaned feathers despite being apparently flightless. Display plumage then? Something else? Maybe Archaeopteryx's ancestors actually were flight-capable, leaving the complex feathers as something of a vestige - though I kind of doubt that. Those complex wing feathers appear to have been pretty widespread among flightless deinonychusaurs, so I would guess that flight came later.

  This somewhat touches on my previous comment, but I was considering some paintings of baby hadrosaurs and perhaps dromeosaurs, covered with tiny downy feathers when I made the heat related comment. It has been suggested dinosaurs had downy feather covering until they were large enough to internally self regulate their temperatures. If indeed those downy feathers were for heat preservation, that would suggest something similar could be linked to environment or location....or no?

Hmm. Well, lots of dinosaurs do hatch with down feathers that are later replaced by their adult plumage - I suppose those are insulatory. Though, I don't think it would be possible for an animal to lose a coat of down and grow scales in its stead. We know dromaeosaurs were fully feathered, but a down-covered hadrosaur chick would imply that adult hadrosaurs either had bald skin or a coat of feathers - not scales. You make a good point though, feathers are good for insulation, so dinosaurs in cold climates would probably need them. I'm just not sure that would also imply overheating for feathered dinosaurs in warm places. Even then, I've read that any animals whose ancestors had feathers would be in the same situation as the adult form of a down-covered chick. That's to say, it would have to either keep the feathers or lose them, not have scales instead. Then again, it's possible for dinosaurs to have both in one place - in which case maybe the feathers could be lost, leaving only scales behind?

Quills, function unknown. I suggest they might have made a great display feature...being kept nominally flattened but when angered or threatened flared up much like a puffball. It is hard to know wether they covered all of the body or just the tail as preserved, however Tianyulong did have them everywhere seemingly.

Oh, that's an interesting idea. Is there any research regarding whether the quills were attached to any muscles that'd allow for that kind of display?

[amargasaurus cazaui]

Pixel you were the first to explain to me the arms on my Pisttacosaurus were not mounted correctly. So  a reputation for more than feathers. I did redo the arms too.
and yes, you do have a reputation for being the feathered fan here.
  As for drama and arguments I did state right up front not doing it myself so, wont even try. If someone else wants to wear themselves out doing it, well by all means...i need a break lol.
  Is it then considered unlikely that Archaeopteryx could itself fly? I had never read or known that...is that something new?
  I am unaware of anything that thus far suggests a use for the quills, but we tend to get them associated with dinosaurs that were small in size and lacked visible or well noticed weaponry. It would make sense as a display to puff up and frighten predators, i would think. I do not know of any evidence whatsoever to support that conjecture however.

[wings]

@amargasaurus cazaui
Here are three papers on feather origin:
http://www.yale.edu/eeb/prum/pdf/Prum_1999_MDE.pdf
http://www.mcorriss.com/Prum_&_Brush_2002.pdf
http://www-hsc.usc.edu/~widelitz/nature.pdf

As for the Liaoning setting, here is a paragraph from the book "The Jehol Fossils": "...It is likely that the environmental changes resulted from the volcanic eruptions caused the mass mortality of birds and other vertebrates. After a brief floating transportation on the surface of the lakes, the dead bodies quickly descended into, and were buried in, the deep water. The abundant volcanic ashes speeded up the deposition process; therefore the dead bodies were preserved rapidly and completely..."

Asymmetrical feathers are normally associated with something to do with aerodynamic. I suppose that is why we only found asymmetrical feathers on the wings instead of on the body of a bird. Flightless birds tend to have symmetrical and/or unvaned feathers. Archaeopteryx has asymmetrical feathers on its wings, so I guess these feathers were used in some way for "flight", although it cannot raise its arms above its shoulders but I think it probably is sufficient to glide while holding its arms straight out (animals we know today tend to have flight strokes with the wings raised above their back regardless whether it is an invertebrate or vertebrate). Perhaps they have developed some kind of flight strokes that doesn't require them to lift their wings above their backs but I wonder how efficient would this motion be? I think this condition is also found in Confuciusornis as well, these animals have large sternums probably indicate powerful flight strokes. Maybe there is really a flying style that doesn't need the arms to raise above the animals back or Confuciusornis are also gliders too...

I'm not sure whether large feathered dinosaurs really would experience overheating if they are placed in the hot climate zone? It is true that a lot of large mammals in the hot climate are almost hairless however there are also animals which is quite hairy as well (i.e. giraffes). 

[Gryphoceratops]

Ever since Yutyrannus was discovered/became public I think its likely every coelurosaur would have had some sort of feathering regardless of size.  Maybe they could have been more scarce on the body for animals from hotter environments but remember, back in the mesazoic its not like any place was really THAT cold by today's standards.  Seasonally cool at the most. 

As for quills on ornithiscians, they have only been discovered in one specimen of psittacosaurus (related to but not likely a direct ancestor of large ceratopsids) and one specimen of tianyulong (a heterdontosaurid).  Did all their relatives have this?  Maybe.  But it could just as easily be an isolated species thing, a sexual dimorphism thing...we need more evidence to make that call for sure. 

[ZoPteryx]

With regards to ornithiscians, I agree with Gryph, we need more evidence before we start reconstructing all non-therapods with feathers.  I personally would reconstruct all small herbivorous dinos with insulation of some type, but that's just my guess.   As for hatchlings of ornithiscians (and sauropods for that matter), feathery insulation would have been very useful for maintaining a high internal body temp needed to process plant matter quickly (this is of course assuming they were warm-blooded).  This makes sense when one considers that some of these animals were growing at least several times larger than an elephant but in much less time.  Once fully grown, or nearly so, feathers could be lost because the increased internal volume would generate enough heat to do the job of the feathers.  So now the question would become, were these animals bald or did they have scales?  Hadrosaur mummies and other ornithiscians show scales, so I think it's likely that if feathers were present at hatching, so were scales; the feathers would grow out from between the scales.  No evidence for this, just another guess.   So far, all quills and such are limited to marginocephalians, so until a hadrosaur, hypsilophodont, iguanodont, or sauropodamorph is found with similar structures, it's still anyone's guess.

As for therapods, again like Gryph said, feathers should be default at least on coelurosaurs; there is too much evidence in favor of this to think otherwise in my opnion.  The main question is did large species keep them through maturity?  My guess would be yes, but perhaps in more limited numbers due to reasons of functionality and cleanlyness.  Assuming Sciurumimus is proven to be a megalosauroid (I've heard of some questioning about this), then feathers in juveniles (at least) in other therapods cannot be ruled out either.

Assuming feathers first evolved for thermoregulation, with small body size being a leading factor in this need, then insulatory structures could potenetial be traced back to the earliest small warm-blooded dinos such as Eorpator.  If Eoraptor and its kin are proven to be more primitive than the saurachian/ornithiscian split, then integument may have been common among all dinos or perhaps even more ancient.  If not, then the quills of ornithiscians may simply be a coincidence.

[wings]

  Okay so the title is a bit flashy. I wanted to set off a discussion about feathers, and quills. I am not sure I ever correctly understand the debate itself well enough to pose the central theme or question. What I wish to see and understand is the varied views on why so many dinosaurs are suggested as having feathers..the fossil evidence and papers that establish it...

Maybe not everyone would be agreeing on this but I think perhaps we can view it this way, if we are looking at the Ornithodira cladogram (http://en.wikipedia.org/wiki/Avemetatarsalia) you will see that pterosaurs were split from the group very early. It appears that most if not all of them have some kind of body filaments – pycnofibers (http://archosaurmusings.wordpress.com/2009/08/05/what-on-earth-are-pycnofibers/). I am not sure whether this actually occurred at the very base of this group (the very first pterosaur) or not and not sure whether these pycnofiber structure are homologous with the protofeathers found on dinosaurs (from the discussion on the archosaurmusings wordpress link above, it seems some people actually thinks that they are very similar structures), so logically regardless whether they are or not this shows the animals "higher up" from the cladogram should probably have the "potential" to develop some kind of "fuzz". I am not saying that they all should have them but just to say that perhaps it shouldn't be too much of an issue for any dinosaurs to develop these structures if required.

[Dinoguy2]

  what I am seeking is input why they seem to occurr or are found in China and not so much the North American area.

In short, North America has no known lagerstatten (that is, limestone or volcanic ash deposits that are capable of preserving fossils with fine details, like those found in NE China and in Germany). Note that the OTHER place producing a good amount of feathered dins/pycnofibred pteros is Solnhoffen, though limestone tends not to preserve as good detail as lakebed ash. In North America, pretty much all we have that's at all similar are limestone deposits from the Western Interior seaway, which are relatively deep ocean and not good for finding non-avialan dinosaurs (though we do have some feather impressions from hesperornitheans found there, skin impressions from mosasaurs, and some isolated feathers from Alabama.). There's also the exquisite lagerstatten of the Green River formation in Wyoming... it's a few million years too late to preserve non-avian dinos, but much of our knowledge of early Cenozoic birds comes from that location.

What purpose is suggested for animals like tianyulong and psittacosaurus to have quills?

No way of knowing right now, probably display, at least in Psittacosaurus (the quills are only present as a mane on the tail so they would have been pretty useless for insulation). Tianyulong has a more hevy covering of filaments which might have served in insulation.

Are feathers and quills related in these species?

That's the $500,000 question right now! If they are, it would mean stage 1 feathers are an ancestral trait for all dinosaurs. Richard Prum for one doesn't think they're related to feathers in any way last I heard , but that was several years ago. There's no good evidence one way or the other right now.

Could feathered dinosaurs be a characteristic of a cooler climate, and perhaps here in North America they were not so likely due to a warmer more temperate climate?

For simple protofeathers, maybe. For true feathers (i.e. Aviremigia and above), probably not, for the same reason as modern birds. Oviraptorosaurs + eumaniraptorans had true, modern feathers identical to birds, and like birds they would have served a variety of functions other than keeping warm (i.e. keeping COOL, waterproofing, etc.).

What dinosaur families do we have evidence for here as feathered?

Here as in North America? We don't have skin impressions from any non-avian dinos here that we would expect to have feathers, so zero direct evidence, but there's no reason to think NA dromies did not have feathers while Asian dromies did.

Purposes the feathers might have served?

Keeping warm, keeping cool, brooding nests, prey capture (look up RPRR hypothesis), flying/gliding, display.

Is it likely that birds evolved first, and ultimately one line of bird became what we now understand are the maniraptors and velocitaptor families?

Depends entirely on what you mean by "bird." This question is meaningless without knowing that! Do you mean something with true feathers (answer in that case: yes)? Something with feathered wings (answer in that case: yes)? Something with feathered wings that uses those wings to glide (answer in that case: probably)? Something with feathered wings that uses those wings to fly (answer in that case: probably not)?

Please note that TRUE birds, like true crocodilians (i.e. those animals that have ALL the characteristics of modern birds) did not evolve until the Late Cretaceous!

[Iguanocolossus]

Call me conservative, but I consider feathers restricted to Maniraptoriformes (don't we have Tyrannosaur skin samples?) and quills only found in Heterodontosauridae  and Psittacosauridae. I would consider the quills on those groups akin to Spinosaur neural spines: a derived trait used for display in select species and not something that would appear in other families.  I remain skeptical. While it's possible that Tyrannosaurus and Triceratops were covered with all sorts of fluff, until more evidence comes I will think of them as naked.

[tyrantqueen]

What about the "mummified" hadrosaurs, Leonardo and Elvis? If there had been feathers or fuzz, surely they would have been preserved too (which they weren't) Is this good evidence that hadrosaurs weren't feathered?

[ZoPteryx]

What about the "mummified" hadrosaurs, Leonardo and Elvis? If there had been feathers or fuzz, surely they would have been preserved too (which they weren't) Is this good evidence that hadrosaurs weren't feathered?

I'd say it's very good evidence, at least as adults.  Until a hatchling mummy is found, juveniles will be open to debate.

[Patrx]

Call me conservative, but I consider feathers restricted to Maniraptoriformes (don't we have Tyrannosaur skin samples?)

A few - but feathers often grow over and among scales. In situations where the scales would leave a fossil, the feathers wouldn't necessarily do the same. As for being limited to maniraptors, the feather-covered Sciurumimus was a basal megalosaur.

I'm also curious about the hadrosaur mummies! Is it possible that their feathers wouldn't leave a trace on a super-detailed fossil like that; or were hadrosaurs  truly devoid of filamentous integument? Also, I thought I remember reading that the idea of a feathered juvenile dinosaur growing into a featherless adult had been disproved (or at least thoroughly refuted) somehow; though I'm not sure about that. Does anyone have any links on the subject?

[tyrantqueen]

Call me conservative, but I consider feathers restricted to Maniraptoriformes (don't we have Tyrannosaur skin samples?)

A few - but feathers often grow over and among scales. In situations where the scales would leave a fossil, the feathers wouldn't necessarily do the same. As for being limited to maniraptors, the feather-covered Sciurumimus was a basal megalosaur.

I'm also curious about the hadrosaur mummies! Is it possible that their feathers wouldn't leave a trace on a super-detailed fossil like that; or were hadrosaurs  truly devoid of filamentous integument? Also, I thought I remember reading that the idea of a feathered juvenile dinosaur growing into a featherless adult had been disproved (or at least thoroughly refuted) somehow; though I'm not sure about that. Does anyone have any links on the subject?

Wasn't it a juvenile?

[Patrx]

As for being limited to maniraptors, the feather-covered Sciurumimus was a basal megalosaur.

Wasn't it a juvenile?

Yes, it was. Why? As I said:

I thought I remember reading that the idea of a feathered juvenile dinosaur growing into a featherless adult had been disproved (or at least thoroughly refuted) somehow; though I'm not sure about that. Does anyone have any links on the subject?

So I don't currently think adult Sciurumimus would've been featherless.

[ZoPteryx]

I thought I remember reading that the idea of a feathered juvenile dinosaur growing into a featherless adult had been disproved (or at least thoroughly refuted) somehow; though I'm not sure about that. Does anyone have any links on the subject?

I remember an article along those lines.  I want to say the main line of evidence presented was that no modern animals undergo such a change in "skin".  However, to that I'd point out that the feathers most birds hatch with are quite different compared to those they'll grow up with and many fish start out as scaleless fry but grow up to have scales.

[amargasaurus cazaui]

What about the "mummified" hadrosaurs, Leonardo and Elvis? If there had been feathers or fuzz, surely they would have been preserved too (which they weren't) Is this good evidence that hadrosaurs weren't feathered?

I'd say it's very good evidence, at least as adults.  Until a hatchling mummy is found, juveniles will be open to debate.

I wanted to interject to inquire here...my understanding was that while Leonardo was a mummy, Elvis was not. Elvis from what I had been shown seems to be a perfectly articulated three dimensional skeleton, unlike Leonardo. I had thought the two best known mummies were Dakota and Leonardo, in fact. Still here is a view of Elvis, so you can see for yourself. A mummy should be fully encased, and have the skin envelope intact or somewhat present, which I see no evidence of here, unless within the field jacket, at the bottom.
Judging from this photo i see no reasonable way this could be evidence for or against ....Moving along to Dakota, the skin envelope for this mummy has proven quite difficult to prep or bring to the surface and display properly. At the last point i was aware of with the dinosaur, there were large areas that were still encased and could be evidence for or against as well, so unless massive progress was made prepping him recently...........I cannot speak for Leonardo however, as to what is visible or not from his skin.
http://www.montanadinosaurdigs.com/dinosaur-discoveries-elvis/

[Patrx]

I thought I remember reading that the idea of a feathered juvenile dinosaur growing into a featherless adult had been disproved (or at least thoroughly refuted) somehow; though I'm not sure about that. Does anyone have any links on the subject?

I remember an article along those lines.  I want to say the main line of evidence presented was that no modern animals undergo such a change in "skin".  However, to that I'd point out that the feathers most birds hatch with are quite different compared to those they'll grow up with and many fish start out as scaleless fry but grow up to have scales.

Huh, I seem to remember the argument against it being a bit more substantial than that  Interesting. I imagine Mesozoic dinosaurs' feathers changed much like those of modern dinosaurs with maturity, but I gotta say that it's tough for me to figure out a reason for complete loss in adults. There again, though, I am no biologist.

[wings]

What about the "mummified" hadrosaurs, Leonardo and Elvis? If there had been feathers or fuzz, surely they would have been preserved too (which they weren't) Is this good evidence that hadrosaurs weren't feathered?

I'd say it's very good evidence, at least as adults.  Until a hatchling mummy is found, juveniles will be open to debate.

In terms of "hadrosaur"skin, here is an interesting article about its preservation (see http://app.pan.pl/article/item/app20120077.html).