Re: Feathering proof

[DinoLord]

Yeah, the green river fossils are really beautifully preserved (though the birds are extremely rare compared to the fish fossils). Interestingly the fish fossils from this site usually don't have the scales preserved despite the high level of bone detail that can be seen in good specimens.

[Dinoguy2]

Yeah, the green river fossils are really beautifully preserved (though the birds are extremely rare compared to the fish fossils). Interestingly the fish fossils from this site usually don't have the scales preserved despite the high level of bone detail that can be seen in good specimens.

Very few of the Yixian fossils preserve scales either, even ones like hadrosaurs. As I've been saying, the conditions needed to preserve feathers and conditions needed to preserve scales are often mutually exclusive

[Seijun]

Question... Why is it that when we don't have direct fossil evidence for feathers in a particular species, many people assume scales to be the default? Lacking any direct evidence for either (and If someone chooses not to consider any indirect evidence), then the likelihood of scales or feathers in a species with no preserved integument should be equal, no?

If we take into consideration that modern birds can have patches that are both scaleless and featherless, and I believe crocodilians also have scaleless areas on the face.. then smooth skin could also be a possibility. Though as far as I know, we don't have any evidence of dinosaur skin that is both scaleless and featherless...

So why do we make scales the default, and not feathers or smooth skin? Why make a default to begin with? Without direct evidence of any particular integument, wouldn't it make the most sense to just say "I don't know" and give them all equal possibility? Again, this is assuming that someone does not want to consider indirect evidence (fossil evidence of integument in related species).

[DinoLord]

I think that's due to people's 'default' vision of dinosaurs as scaly animals. That's the way pretty much all of us saw them growing up, and its ingrained in many people's minds.

[Newt]

You're absolutely right, Seijun. There's a big and often overlooked difference between "scientific conservatism", in which your hypotheses are limited by available evidence, and "social conservatism", in which your hypotheses are limited by what you are used to. People get them mixed up when they insist that it is more conservative to assume scaly skin in a dinosaur lineage without known skin impressions, related to both scaly and feathery groups.

[Gwangi]

Spot on observation Seijun, it is something that has bothered me for a long time. I said about as much in one of the Battat threads, the one that drove Dan LaRusso away...apparently. I used therizinosaurs as an example. When you have evidence for feathers on one or a few species but no evidence of scales why would you assume any of them had scales to begin with? The null hypothesis (or default) should be that the animal preserved without integument or lacking sufficient evidence of integument should be assumed to have had whatever its closest relative had for which integument is preserved. So we have feathers for the therizinosaur group, therefore feathers should be the assumed integument. And it is all very frustrating trying to drive that point home.
Something like Tyrannosaurus makes things more difficult because we have preserved scales and no feathers BUT we have feathers on related forms. It could have had both, or maybe it was scaly, or maybe it was mostly just bare skin (which is more likely if it was secondarily featherless) and that is why I'm generally much more relaxed concerning depictions of Tyrannosaurus.

[Patrx]

This new Spinosaurus material has got me thinking - could this be qualified as noteworthy evidence for a featherless (or nearly featherless) condition for Spinosaurus? Animals that adapt strongly for aquatic or even semiaquatic lifestyles generally show reduced pelage, like hippos, whales, and modern crocolidians. I suppose the obvious counterpoint would be penguins, another line of semiaquatic dinosaurs, which have simply developed different kinds of feathers rather than losing them completely.

[stargatedalek]

(to our current knowledge) feathers have never been lost in full, even on aquatic animals, just because it happens to hair/fur when an animal becomes aquatic doesn't mean the same applies to feathers
more than just penguins, cormorants, loons, anhingas, auks, diving ducks, hesperornids, the list goes on of diving dinosaurs with feathers

given this, (assuming spinosaurus ancestors had complex feathers) I don't see any reason to assume it lost them because it was aquatic

[Sim]

Each family of coelurosaurs have evidence of at least one of their members having feathers.  Due to the type of feathers seen in these coelurosaurs, and the close relationship between them, I think it's almost certain every coelurosaur up to a certain size was feathered.  There's no reason to think otherwise, and the huge amount of extremely diverse extant birds - which are coelurosaurs - supports this even more.

The largest extant birds, and extinct birds with known feathering are much smaller than many coelurosaurs.  So, I think it's hard to know how feathered giant coelurosaurs were, since there's a trend of reduced feathering in large flightless birds.  Yutyrannus' feathering is expected, as it lived in quite a cold environment with an average annual temperature of 10°C.  This doesn't help to give a better idea of feathering on huge coelurosaurs living in warm environments.

This post on DinoGoss: http://dinogoss.blogspot.co.uk/2011/02/heat-feathers-and-half-arsed.html talks about the effects of reduced feathering on birds, and has interesting pictures of the featherless underwing area of the Ostrich and Greater Rhea.

The bigger an animal gets, the less easily it can lose heat.  This isn't a problem for animals that live in cold environments, but it makes me wonder about giant coelurosaurs that lived in warm environments.  From what I've understood, it seems possible they could have little or no feathers, as feathers could interfere with their ability to effectively radiate heat.  Scales found on Tyrannosaurus, Tarbosaurus and Gorgosaurus on parts of their bodies where Yutyrannus had feathers seems to support this.

I know feathers can grow between scales.  The only place I know this occurs is on owl feet.  Owls are farsighted.  Being unable to see anything within a few centimetres of their eyes clearly, the foot feathers allow them to feel caught prey.  Feathers growing among scales needs a reason.  There doesn't seem to be a likely one for the bodies of huge dinosaurs.

I think that a dinosaur's size, build, environment, and lifestyle could make some of the larger coelurosaurs have more reduced feathering than on an ostrich, maybe they might even be featherless.

[HD-man]

This new Spinosaurus material has got me thinking - could this be qualified as noteworthy evidence for a featherless (or nearly featherless) condition for Spinosaurus? Animals that adapt strongly for aquatic or even semiaquatic lifestyles generally show reduced pelage, like hippos, whales, and modern crocolidians. I suppose the obvious counterpoint would be penguins, another line of semiaquatic dinosaurs, which have simply developed different kinds of feathers rather than losing them completely.

No offense, but crocs are a bad example, given that their ancestors didn't have pelage. That does me make wonder, though, whether the dorsal scales of Spinosaurus in particular & spinosaurs in general were armored like those of crocs.

[Patrx]

Hm, interesting responses! I suppose penguins were the first to mind because of how strongly adapted to water they are, but other diving birds are also relevant.

Owls are farsighted.  Being unable to see anything within a few centimetres of their eyes clearly, the foot feathers allow them to feel caught prey.

That's interesting! I didn't know that, but it makes sense.

No offense, but crocs are a bad example, given that their ancestors didn't have pelage.

Not in the literal sense (mamalian hair), but I suppose that, as archosaurs, at least the most basal crocodylomorphs might have borne some kind of filamentous structures.

[Ultimatedinoking]

Hi every one, I'm back! 

[amargasaurus cazaui]

Has anyone read this or have anything to comment?

http://www.uncommondescent.com/intelligent-design/barb-birds-are-reallybirds/

[CityRaptor]

Well, it is an Intelligent Design article, and ID, as we all know, is creationism with a new hat.

[Manatee]

University Of North Carolina paleontologist Alan Feduccia...

Oh dear.

Plus, like CityRaptor stated, all this is is another creationist article bashing evolution.

[Gwangi]

Typical ID propaganda. I love how they'll back someone like Alan Feduccia knowing full well that he supports evolution (just not from dinosaurs, he still agrees that birds are archosaurs). But they'll do that simply to stir the pot and create doubt about mainstream science.

[stargatedalek]

"Alan Feduccia"
all you need to know about the article

[Newt]

I have skimmed the second article referenced, that supposedly shows theropods could not have bird-style repiratory systems due to not having bird-style fixed femora, and therefore could not be the ancestors of birds. There is a fundamental flaw in the reasoning: NOTHING other than birds has bird-style fixed femora, and therefore, by the researcher's logic, NOTHING can be the ancestor of birds. Plus, this narrative conveniently ignores the fact that Archaeopteryx does not have advanced bird-style fixed femora (which presumably evolved in connection with tail reduction, to help bring the legs under the forward-shifted center of mass), indicating either that the whole femur-abdominal air sac connection evolved within the birds and therefore is totally irrelevant to determining their ancestry, or else that Archaeopteryx is not a bird or bird-ancestor. I will comment further after reading the article more thoroughly.

[Megalosaurus]

Has anyone read this or have anything to comment?
http://www.uncommondescent.com/intelligent-design/barb-birds-are-reallybirds/

Hello.

One factor that has long been a source of consternation is that the finger digits of theropods and birds do not appear to match. While theropods seemingly carried digits 1,2 and 3 of the pentadactyl arrangement, birds display what scientists believe to be digits 2,3 and 4

That is still "a source of consternation", but many people just overlook it. A few people have explanationas like this:

Xu and Clark [...] claim[...] that theropod digits have historically been misidentified

But to date there's no general consensus about this subject. This is just ignored most of the time.

Another important thing to have in mind is the bird fossil record. I'll take a few examples:
Archaeopteryx is dated about 150-140 M.Y. but Confuciusornis (a much more modern bird) lived from roughly 161-100 MY. The fact is that birds existed before 161 MYA. But how long ago?
Its still debatable but if Protoavis is correctly interpreted then:

The most remarkable thing about Protoavis is that, although it predates Archaeopteryx by 75 million years, it is considerably more advanced than Archaeopteryx...Protoavis is more closely related to modern birds than is Archaeopteryx.
—Sankar Chatterjee

Any way all maniraptorian feathered dinosaurs from china are younger than 161 MY. For example Yixian Formation is from 125–121 MYA, so no bird ancestors there.

That are the facts that we all should think of, it doesn't matter if we are part ot the BAD or of the BAND. 

PD.- BAD=Birds are Dinosaurs      |     BAND=Birds Are Not Dinosaurs

[Dinoguy2]

Has anyone read this or have anything to comment?
http://www.uncommondescent.com/intelligent-design/barb-birds-are-reallybirds/

Hello.

One factor that has long been a source of consternation is that the finger digits of theropods and birds do not appear to match. While theropods seemingly carried digits 1,2 and 3 of the pentadactyl arrangement, birds display what scientists believe to be digits 2,3 and 4

That is still "a source of consternation", but many people just overlook it. A few people have explanationas like this:

Xu and Clark [...] claim[...] that theropod digits have historically been misidentified

But to date there's no general consensus about this subject. This is just ignored most of the time.

Another important thing to have in mind is the bird fossil record. I'll take a few examples:
Archaeopteryx is dated about 150-140 M.Y. but Confuciusornis (a much more modern bird) lived from roughly 161-100 MY. The fact is that birds existed before 161 MYA. But how long ago?
Its still debatable but if Protoavis is correctly interpreted then:

The most remarkable thing about Protoavis is that, although it predates Archaeopteryx by 75 million years, it is considerably more advanced than Archaeopteryx...Protoavis is more closely related to modern birds than is Archaeopteryx.
—Sankar Chatterjee

Any way all maniraptorian feathered dinosaurs from china are younger than 161 MY. For example Yixian Formation is from 125–121 MYA, so no bird ancestors there.

That are the facts that we all should think of, it doesn't matter if we are part ot the BAD or of the BAND. 

PD.- BAD=Birds are Dinosaurs      |     BAND=Birds Are Not Dinosaurs

Confuciusornis lived in the Yixian and Jiufotang formations from 124 to 120 mya. There are no protobirds more advanced than Archaeopteryx from the 160 mya Tiaojishan formation, only things like Anchiornis, Aurornis, Scansoriopteryx, and Eosinopteryx. I'd say all those are around the same "level" as Archie though their exact positions as more or less primitive are debatable. But certainly no short tailed birds are known from prior to 130 mya when the first enantiornithian appears.