All Dinosaurs may have had feathers.

[Gwangi]

Am I wrong in remembering that there have been infant sauropod skin impressions?

infant and adult skin impressions for sauropods.

It's common sense that filament like feathers are much harder to preserve than thick scales, just like Patrx said, if you were paying attention.

Wow...you know, maybe he didn't refresh himself on a thread that was started back in May? 

Anyway, some modern birds have feathers and scales that overlap each other so it is certainly possible dinosaurs did as well.

[tyrantqueen]

I don't think dinosaurs that possessed dermal osteoderms, such as ankylosaurus, were feathered very much, if at all. Something like the peach fuzz of an armadillo:

[Hermes888]

It's more likely that feathers started out in the theropod lineage instead of starting out with all dinosaurs (and pterosaurs) with multiple groups losing feathers over time. If infant sauropods didn't have any kind of feather covering, I find it unlikely that they would have feathers in any point of their lives.

It's common sense that filament like feathers are much harder to preserve than thick scales, just like Patrx said, if you were paying attention.

That post was made in May. 

[Lythronax]

Hi all,

In my first post in this thread I wanted to join two related threads because, among other things, I think that in this thread there were more people commenting, giving their opinion and providing information. 

It's more likely that feathers started out in the theropod lineage instead of starting out with all dinosaurs (and pterosaurs) with multiple groups losing feathers over time.

First, about what Hermes888 says, I already said something about it in another thread, so I write out the link to avoid a long rant 

http://www.dinotoyblog.com/forum/index.php/topic,1804.msg47581.html#msg47581

I think that nowadays it's quite clear that the origin of protofeathers dates back to Arcosauria, that is, before dinosaurs. Because the "genetic machinery" to create feathers is already present in crocodiles and in crocodiles signs of an endothermic past have been found.

Now, I think that the picture you posted, Gwangi, is very interesting (By the way, I'm curious to know which bird species is represented in the picture). The reason is because this picture indicates that I have probably misunderstood the content of the papers I cite in the other thread. (see link before)

For scale formation the inhibition of feather formation is necessary. So this led me to think that in a same area of skin these two structures could not coexist. As tyrantqueen pointed out, birds generally present feathers in areas with smooth skin. But I was mistaken, as Gwangi shows. Thanks for making me think about this question 

[Lythronax]

I never denied the evidence that scale fossilization is easier than feather fossilization. For this reason I think we have to focus on skin imprints to see indirectly whether dinosaurs could have feathers, and to see whether these were more or less profuse. If we look at the picture of the bird that Gwangi posted, we can see that the feathers are present in the areas of smooth skin between the scales (the equivalent of the smooth skin that tyrantqueen talked about). If we pay attention at the pattern of scales, we can see that, unlike in most skins in reptiles and birds, the scales are quite apart from each other (they are separated even by a "single-scale" distance). This shows us that for feathers to exist between scales, it is necessary that the area of smooth skin between scales be larger. If the area of this interscale skin is smaller, the density of feathers is also lower. And if the area of this smooth skin is negligible, so there are very few feathers or none at all.

Having this in mind, we can examine remains of dinosaur skin preserved until today to see whether different kinds of dinosaurs had feathers and whether the feather cover was profuse.

To be fast, I provide a link to one of the papers I mentioned in the other thread:

http://www.ivpp.cas.cn/cbw/gjzdwxb/xbwzxz/200911/P020091104362654347399.pdf

In this paper, pictures of the scales of a sauropod, a stegosaurian and a ceratopsian can be seen. In all these pictures it can be perfectly seen that the scale pattern is dense, that is, that the distance between the scales is very small. So it could be the case that the number of feathers between the scales is very small or that there are no feathers at all. But we have to bear in mind that these are remains of dead animals and that we don't know how long they were exposed to the elements before being buried. Therefore, the skin could have become dry and shrunk before going fossilized, which would give us the false impression of a distance between the scales much smaller than the actual one. The same could happen with other famous skin remains, like the tyrannosaur Wyrex. So it seems that we are back to where we were before, isn't it? Not at all.

There are other skin remains that can't have undergone all these "environmental" problems. Researchers have found skin remains of a Titanosaur embryo that was inside the egg, perfectly sealed (that's why the skin was preserved). They have also found skin remains of the Edmontosaurus Dakota, which was buried by mud from the river shortly after dying (it still had organs and a crocodile inside). Therefore, in these two cases, the skin is perfectly preserved. And in these two cases, the distance between scales is very small. This indicates that in these two groups there were almost no feathers or none at all.

Besides, as tyrantqueen pointed out, there is dinosaur skin, like in ankylosaurs, that was very ossified like that in crocodiles, with the scales very close together. The same happens with the skin of advanced ceratopsians, like Triceratops:
http://www.omniology.com/dinosaur-skin.htm

So in these two kinds of dinosaurs with ossified skin, difficult to dry out, the small distance between scales doesn't allow for the existence of feathers, or these were at most very sparse.

Going back to the cases I mentioned, if we pay attention to the pictures in the paper, the scales of the stegosaurian and ceratopsian (a Psittacosaurus) fit together perfectly like in the Triceratops I mentioned earlier. Then, it's not insane to think that smooth skin between scales would be scarce. So the number of feathers in this scaly skin would be very low or 0. This is consistent with what can be observed in the Psittacosaurus fossil that has feathers. The feathers are only on the dorsal part of the tail, whereas on the rest of the body there are no feathers. This assumption based on the fit between scales would be also correct in the case of Wyrex. On the contrary, this assumption would not be possible in the case of the skin of Mamenchisaurus. But because researchers have discovered the skin of a Titanosaur embryo that is well preserved and because this skin is equal to the skin of Mamenchisaurus, we know that the scales were very close together.

I have not seen any picture of dinosaur skin with features similar to the picture posted by Gwangi. I can be mistaken, but insofar as nobody tells me about a specimen I I'm unaware of (which can perfectly be the case, because I don't know many specimens), I would say that dinosaur species with known fossil imprints of scaly skin would not have a thick cover of protofeathers.

In the case of other species, like Gorgosaurus, I can't say whether they had a thick feather cover or not.

... That said, it seems that Philip Currie found naked skin belonging the neck of a Gorgosaurus (that is, without feathers or scales). I'm not aware of any thorough study of this individual, so for the moment nothing sound can be said about this skin. Maybe these fossil remains have been misinterpreted, just bear in mind that carcasses undergo some degree of decomposition before fossilizing. If this skin were really naked, this could mean that Gorgosaurus had a seasonal feather cover: feathers in the cold season that were lost with the onset of the warmer season.
....

So, having said that these scaly dinosaurs would not have furry feather covers, let's talk about whether they would have only scales or a sparse feather cover. As I said in another post where I introduced myself, biological structures have their function, they don't exist just because they look cool.  Then, if the protofeather cover was so spare that would not be able to thermally insulate the animal, why the hell should the animal have it? One option would be coloration, like in the case of nuptial coloration. But the type of feather that the majority of dinosaurs would have would be primitive (feathers type I), so the color gamut would not be as wide as in more derived feathers. Besides, extant reptiles don't need feathers to have astounding nuptial colorations. Even more, the skin with protofeathers would restrict the gamut of colors (e.g. blue and UV) that the naked skin of reptile does allow. Therefore, from my point of view, I can only think that, like in extant elephants and rhinos, in scaly dinosaurs these protofeathers (type I) could have only a sensory function like cat whiskers. So protofeathers in these groups would be confined in areas where a heightened sense of touch would make sense, as on the snout.

Well, that's all. Sorry for the delay, my English is not good.

[Dinoguy2]

For scale formation the inhibition of feather formation is necessary.

This argument is based on evolutionary developmental biology, or evo-devo. It assumes that the genetics of modern animals have not changed, ever, and that the way genes are expressed today is exactly the same as in their genetic ancestors. Which is ridiculous. Even if this argument is true for most modern birds, it's not safe to assume it was true of non-avian dinosaurs.

Evo-devo is the same science that once claimed you can trace evolutionary ancestry by looking at embryo development, a hypothesis that was destroyed in the late 20th century giving lots of fodder to creationists...

[Brontozaurus]

Oh and we seem to have found a basal ornithiscian with complex feathers.

[Balaur]

Holy crap.

[HD-man]

Am I wrong in remembering that there have been infant sauropod skin impressions?

Not just skin impressions, but "full-body skin casts" ( http://dml.cmnh.org/2011Sep/msg00129.html ).

It's common sense that filament like feathers are much harder to preserve than thick scales, just like Patrx said, if you were paying attention.

Based on what I've read (E.g. See "The feather-scale dichotomy" & the sources therein: http://reptilis.net/2012/07/23/feathers-on-the-big-feathers-on-the-small-but-feathers-for-dinosaurs-one-and-all/ ), "the two integumentary types appear to be mutually exclusive." I also found Jura's "Feathers for Tyrannosaurs" comments & the sources therein to be helpful: http://phenomena.nationalgeographic.com/2013/12/16/feathers-for-tyrannosaurs/

Anyway, some modern birds have feathers and scales that overlap each other so it is certainly possible dinosaurs did as well.

Assuming I read it correctly, the Jura quote covers the issue of feathered feet.

This argument is based on evolutionary developmental biology, or evo-devo. It assumes that the genetics of modern animals have not changed, ever, and that the way genes are expressed today is exactly the same as in their genetic ancestors. Which is ridiculous. Even if this argument is true for most modern birds, it's not safe to assume it was true of non-avian dinosaurs.

Evo-devo is the same science that once claimed you can trace evolutionary ancestry by looking at embryo development, a hypothesis that was destroyed in the late 20th century giving lots of fodder to creationists...

The above quote is either very ignorant or very misleading.

1stly, like the aforementioned creationists, it seemingly assumes that Haeckel's work is relevant to modern Evo-Devo (which isn't the case: http://www.talkorigins.org/faqs/wells/haeckel.html ).

2ndly, it seemingly ignores the fact that Evo-Devo "has giv-en us a powerful tool for probing the origin of feathers" ( http://prumlab.yale.edu/sites/default/files/prum_n_brush_2003_origin.pdf ).

Quoting Jura (See "The feather-scale dichotomy": http://reptilis.net/2012/07/23/feathers-on-the-big-feathers-on-the-small-but-feathers-for-dinosaurs-one-and-all/ ):

This all-or-none principle and antagonistic relationship of feathers and scales has been doubted in the paleo literature, with some authors arguing that Evo-Devo studies actually support a hodge-podge scale-feather relationship (Chiappe & Gohlich 2010, Rauhut et al. 2012). However, the references that are often cited for this do not actually support this view. Some such as Chang et al 2009, Widelitz et al. (2000, 2003) and Dhouailly et al. (1980) point to evidence of latent feather forming ability in avian scales. This ability was discovered through manipulation of scale epidermis by incorporating different compounds (e.g., B-Catenin, Retinoic Acid) during development. Results of these studies have shown that feathers can be induced from scale epidermis at certain times during development. However just because a feather was developing does not indicate that scales and feathers made good bedfellows. Quite the opposite in fact. As Dhouailly (1980) states:

It is clear, however, in view of the existence of domestic breeds of fowl with feathered feet (genetic ptilopody), that RA [Retinoic Acid] somehow interferes with scale morphogenesis and thereby reveals  a latent ability of avian foot integument to produce feathers. Apparently the formation of scales requires additional and possibly inhibitory region-specific information on top of the trivial and 'ubiquitous feather message' (Dhouailly,1978). Retinoic acid,by weakening the scale message, would leave the feather message free to be expressed.

To put it another way: scale formation in birds requires active feather suppression.

[Dinoguy2]

Am I wrong in remembering that there have been infant sauropod skin impressions?

Not just skin impressions, but "full-body skin casts" ( http://dml.cmnh.org/2011Sep/msg00129.html ).

It's common sense that filament like feathers are much harder to preserve than thick scales, just like Patrx said, if you were paying attention.

Based on what I've read (E.g. See "The feather-scale dichotomy" & the sources therein: http://reptilis.net/2012/07/23/feathers-on-the-big-feathers-on-the-small-but-feathers-for-dinosaurs-one-and-all/ ), "the two integumentary types appear to be mutually exclusive." I also found Jura's "Feathers for Tyrannosaurs" comments & the sources therein to be helpful: http://phenomena.nationalgeographic.com/2013/12/16/feathers-for-tyrannosaurs/

Anyway, some modern birds have feathers and scales that overlap each other so it is certainly possible dinosaurs did as well.

Assuming I read it correctly, the following Jura quote covers the issue of feathered feet.

Evo-devo is the same science that once claimed you can trace evolutionary ancestry by looking at embryo development, a hypothesis that was destroyed in the late 20th century giving lots of fodder to creationists...

The above quote is either very ignorant or very misleading.

1stly, like the aforementioned creationists, it seemingly assumes that Haeckel's work is relevant to modern Evo-Devo (which isn't the case: http://www.talkorigins.org/faqs/wells/haeckel.html ).

2ndly, it seemingly ignores the fact that Evo-Devo "has giv-en us a powerful tool for probing the origin of feathers" ( http://prumlab.yale.edu/sites/default/files/prum_n_brush_2003_origin.pdf ).

Quoting Jura (See "The feather-scale dichotomy": http://reptilis.net/2012/07/23/feathers-on-the-big-feathers-on-the-small-but-feathers-for-dinosaurs-one-and-all/ ):

This all-or-none principle and antagonistic relationship of feathers and scales has been doubted in the paleo literature, with some authors arguing that Evo-Devo studies actually support a hodge-podge scale-feather relationship (Chiappe & Gohlich 2010, Rauhut et al. 2012). However, the references that are often cited for this do not actually support this view. Some such as Chang et al 2009, Widelitz et al. (2000, 2003) and Dhouailly et al. (1980) point to evidence of latent feather forming ability in avian scales. This ability was discovered through manipulation of scale epidermis by incorporating different compounds (e.g., B-Catenin, Retinoic Acid) during development. Results of these studies have shown that feathers can be induced from scale epidermis at certain times during development. However just because a feather was developing does not indicate that scales and feathers made good bedfellows. Quite the opposite in fact. As Dhouailly (1980) states:

It is clear, however, in view of the existence of domestic breeds of fowl with feathered feet (genetic ptilopody), that RA [Retinoic Acid] somehow interferes with scale morphogenesis and thereby reveals  a latent ability of avian foot integument to produce feathers. Apparently the formation of scales requires additional and possibly inhibitory region-specific information on top of the trivial and 'ubiquitous feather message' (Dhouailly,1978). Retinoic acid,by weakening the scale message, would leave the feather message free to be expressed.

To put it another way: scale formation in birds requires active feather suppression.

Jura is really committed to the idea that feathers and scales are mutually exclusive. He seems to believe that the genetics of feather development have never changed during 165 million years or more of evolution, which is a borderline creationist argument. He admits in the blog comment thread that any clear indication of both feathers and scales on the legs tail or torso would demolish his hypothesis, but years ago I showed him the same pics of owl feet that Gwangi posted above and he brushed them aside as a different mechanism. This is moving the goalposts. We'll see how he responds to the supposed ornithischian with complex feathers (if they're not just filaments, which he doesn't count as feathers). I don't know of any mainstream paleontologists who agree with him--all others seem to think feathers and scales can exist simultaneously.

Note that Jura doesn't just think they can't exist on the same spot. He thinks it' impossible, for example, for there to be feathers only on the tail and scales only on the torso or upper legs. He considers the lower legs of birds to be a highly evolved exception, but then can't explain why it's impossible for other exceptions to have evolved in other kinds of dinosaurs.

Not that this means the argument is wrong, but anytime you read online about this supposed feather/scale dichotomy, it's him or people linking to him. He's almost like the Dave Peters of this subject.

[HD-man]

Jura is really committed to the idea that feathers and scales are mutually exclusive. He seems to believe that the genetics of feather development have never changed during 165 million years or more of evolution, which is a borderline creationist argument. He admits in the blog comment thread that any clear indication of both feathers and scales on the legs tail or torso would demolish his hypothesis, but years ago I showed him the same pics of owl feet that Gwangi posted above and he brushed them aside as a different mechanism. This is moving the goalposts.

1stly, it seems hypocritical to refer to Jura's argument as "borderline creationist", given that (as I pointed out in my previous post) you made a seemingly creationist argument in your previous post.

2ndly, IDK about your debate w/Jura, but I do know that he explained why feathered feet are the exception that supports the rule (See the Jura quote in my previous post). I should add the caveat, though, that if said debate went down as you described, then there was no goalpost moving b/c Jura said "legs tail or torso" & you showed him feet.

I don't know of any mainstream paleontologists who agree with him--all others seem to think feathers and scales can exist simultaneously.

For what it's worth, "Prum, Dyck, Brush and others cite the work by Sawyer et al. as being consistent with their own model" ( http://blogs.scientificamerican.com/tetrapod-zoology/2012/05/07/thor-hanson-feathers-review/ ). That's what Naish said in reference to Prum & Dyck 2003 ( http://prumlab.yale.edu/sites/default/files/prum_n_dyck_2003.pdf ). Now that I think of it, how many other "mainstream paleontologists" have actually done any Evo-Devo work?

Note that Jura doesn't just think they can't exist on the same spot. He thinks it' impossible, for example, for there to be feathers only on the tail and scales only on the torso or upper legs. He considers the lower legs of birds to be a highly evolved exception, but then can't explain why it's impossible for other exceptions to have evolved in other kinds of dinosaurs.

Actually, Jura has explained why "other exceptions" are possible, but "not very probable" (See the 2nd Jura quote).

Not that this means the argument is wrong, but anytime you read online about this supposed feather/scale dichotomy, it's him or people linking to him. He's almost like the Dave Peters of this subject.

While Jura isn't my favorite source (I don't even know his real name, let alone his scientific credentials), comparing him to Peters is very misleading (if not just plain wrong): On the 1 hand, you have a knowingly fake scientist whose arguments are based (almost) exclusively on his knowingly flawed work; On the other hand, you have an unknown whose arguments are based on the real actual work of real actual scientists (E.g. Sawyer et al.); It's also worth re-mentioning the fact that the latter has (among other things) "giv-en us a powerful tool for probing the origin of feathers" ( http://prumlab.yale.edu/sites/default/files/prum_n_brush_2003_origin.pdf ). This brings me to why the "feather-scale dichotomy" is so convincing compared to the "hodge-podge scale-feather relationship": On the 1 hand, Jura has provided multiple lines of evidence in support of said dichotomy (See the 1st Jura quote), including the fossil record & EPB; On the other hand, all you have to show for said relationship is the issue of feathered feet (which, as I pointed out earlier, Jura has already covered) & Argument from Authority ("I don't know of any mainstream paleontologists who agree with him--all others seem to think feathers and scales can exist simultaneously").

Quoting Jura (I italicized the Martyniuk quotes: http://phenomena.nationalgeographic.com/2013/12/16/feathers-for-tyrannosaurs/ ):

I'm not proposing that feathers magically appeared, but I am trying to make the same point that I've been harping on for years now. Namely that feathers and scales are not these interchangeable structures that you can just swap out like a hat. One reason why I say this is related to what we know about the evolutionary development of feathers.

Briefly, studies on the embryos of chickens, zebrafinches, and other birds have observed that feather formation follows a fairly stereotypical pattern (Hamburger and Hamilton 1951, Alibardi 2002). Feather primordia (the beginnings of feathers) start to develop first along the head, back, tail and torso. After this, feather primordia form along the proximal thigh and part of the humerus. Finally they continue down to cover all of the arms and various degrees of the legs. Finally after all feather primordia have started forming, the scales start coming in along the tibiotarsus.
To give one an idea of the time it takes for all this to happen, Hamburger and Hamilton (1951) looked at developing white leghorn chicks across the entire span of their development (21 days). Feathers did not start forming until day 6. They did not reach the tibia until day 10, and scales didn't start forming until day 11. Prior to this the skin was completely smooth, devoid of all integument. This developmental distribution is remarkably similar to the distribution of scale formation in alligators (Alibardi & Thompson 2000). This similarity between the two extant members of Archosauria suggests that the developmental mechanism for scale and feather distribution is conserved and thus was likely present in dinosaurs too. The presence of feather formation before scale formation in birds, coupled with data from intentional mutations of chicken epidermis (namely the injection of inhibitors to various regulatory genes) indicate that bird scales are a more recent evolutionary product than feathers (e.g., Sawyer et al. 2005). Taken together this suggests that feathers came about by taking over the scale developmental pathway. There are now a fairly hefty amount of studies out there that support the original argument that feathers evolved from scales. The difference this time is that they did so at a much earlier stage in scale development (as opposed to just being elongate scales). Because of this, and the fact that the distribution pattern is so remarkably similar it is likely that the mutation(s) that caused the formation of the first protofeather likely affected the body as a whole, rather than stepwise. Later a separate regulatory mutation occurred prior to the cascade leading to feather formation along the tibiotarsus. This suppression occurred at an early enough stage to allow for the re-evolution of scales in this region. This is further bolstered by the fact that reticulate "scales" in birds appear to actually be highly suppressed feather buds (Dhouailly 2009). Because these are regulatory gene changes the resulting mutation would look very much like an evolutionary leap rather than a series of incremental steps. We have evidence to suggest that this has happened with numerous other animals throughout time too (e.g., the evolution of snake bodies from lizard bodies may largely involve changes to regulatory pathways rather than individual genes). Regulatory genes allow evolution to proceed in leaps rather than baby steps. I suspect that this is what occurred during the evolution of feathers. So far the fossils appear to support this (filamented all over Yutyrannus. Proofeathered all over Microraptor and Anchiornis. Protofeathered everywhere but the tibiotarsus for NGMC 91).

A key thing to keep in mind for all of this is that avian scales re-evolved and are not just a reversal to reptilian scales. Avian scales form from a placode similar to feathers (Sawyer & Knapp 2003). Reptile scales do not. This means one cannot just turn off feather development and expect to get a scaly bird. The scales on the tibiotarsus and foot are a unique development, whereas the naked skin on male turkeys, old world vultures, and ostriches is the more typical result of feather loss.

As a follow up, the evo/devo argument is at least testable. One fossil specimen with unambiguous feathers and scales on the body would show that at least the "evo" part of this work is simply wrong. There is reportedly one specimen like this in press, with a fluffy body but scaly legs and tail.

First, much has been made of Godefroit's specimen despite it not being published. The paper for that specimen is currently being written and is not in press. At the moment it is not much more than anecdotal. Secondly, SVP abstracts have a ridiculously large lead time on them (8 months). Much of the work described in these abstracts has usually not been done by the time of submission, which is why so many talks and even posters wind up deviating from their abstracts.This means that we can't be certain of the description and (especially) the interpretations of this animal in the abstract. All the more so since the authors were unable to deliver their talk this year. That the internet continues to freely talk about this specimen as if it were published, only serves to hurt it in the long run. Lastly, be mindful of your use of the word: feather.

Jura, would you use the evo/devo evidence to rule out the discovery of a species with scales on some discrete parts of the body (tail, head, upper leg) but feathers on others? What exactly does the evo/devo model predict we should NOT find?

As I understand it, the Evo-Devo model would predict that feathers and protofeathers should be expected on all parts of the body of a dinosaur that had them, with the possible exception of the tibiotarsus and foot, depending on where the animal fell within the dinosaur family tree. More basal feathery guys would be expected to be feathered from head to toe (e.g., Microraptor) whereas later guys would dial it back on the feet (NGMC 91). Though even then the latter could have evolved numerous times. It would not predict a scaly hide with a feathery mohawk, or any other half and half style integument association.

Note that this is for feathers and protofeathers, not for all filaments. It is possible that there are other filamented structures out there that have no relation to feathers or scales (e.g., the bristles of a turkey beard) and thus will have different associations. This is why it's extremely important that these new finds have their ultrastructure examined to determine actual epidermal association as well as to better identify what we are looking at. Bringing things back to Goldefroit's animal, I was happy to see Danielle Dhouailly as one of the coauthors on the abstract. She is a major player in the Evo-Devo world. Hopefully this means that this new find is actually going to get the extensive examination needed before anyone makes any bold claims about fuzziness homology in dinosaurs.

References

Alibardi, L. 2002. Keratinization and lipogenesis in epidermal derivatives of the zebrafinch, Taeniopygia guttat castanotis (Aves, Passeriformes, Ploecidae) during embryonic development. J. Morph. 251:294–308.

Alibardi, L., Thompson, M. 2001. Fine structure of the developing epidermis in the embryo of the American alligator (Alligator mississippiensis, Crocodilia, Reptilia). J. Anat. 198:265–282.

Dhouailly, D. 2009. A new scenario for the evolutionary origin of hair, feather, and avian scales. J. Anat. 214:587–606.

Hamburger, V., Hamilton, H.L. 1951. A series of normal stages in the development of the chick embryo. J. Morph. 88:49–92.

Sawyer, R.H., Rogers, L., Washington, L., Glenn, T.C., Knapp, L.W. 2005. Evolutionary origin of the feather epidermis. Dev. Dyn. 232:256–267.

Sawyer, R.H., Washington, L.D., Salvatore, B.A., Glenn, T.C., Knapp, L.W. 2003. Origin of archosaurian integumentary appendages: The bristles of the wild turkey beard express feather-type B keratins. J. Exp. Zool. (Mol. Dev. Evol.) 297B:27–34.

Quoting Jura (I italicized the Martyniuk quotes: http://phenomena.nationalgeographic.com/2013/12/16/feathers-for-tyrannosaurs/ ):

...there are dinosaur specimens that show reticulate scales on parts of the body and scutes on others (Concavenator has reticulate scales on the hind limbs with bird-like tarsal scutes AND croc- or bird-like scutes on the belly. Triceratops also appears to have belly scutes). Furthermore, the scales found in tyrannosaur specimens are all reticulate, making them possible "scales" in name only.

I think you are confusing reticulae with tubercular scales. These are pretty common in dinosaurs, with tyrannosaurids being no exception. The scale impressions look very similar to the tubercular scales we see in geckos and chameleons (for instance). The image I used on my blog did not do the best job of distinguishing scutes from scutellae and (especially) reticulae. It's remarkably difficult to get a good bird foot image online. In my experience reticulae tend to be more like sharp little protrusions coming off the foot (they remind me a bit of keeled scales). Actually this is a pretty good shot. of bird reticulate "scales."

If the tarsal scutes and reticulate foot scales of avialans and NGMC 91 resulted from suppression of feather development, could this not have also happened independently and on other parts of the body in other stem-bird lineages? If not, why not? What is inherent to feather suppression on the tarsus and foot that makes this the only possible site for reticulate scale formation from feather buds?

Is it possible? Yes, but it's not very probable. You are arguing for a trait that might have existed in dinosaurs but that doesn't leave behind an osteological correlate and isn't seen in any of the extant animals that bracket them. This is a level 3 prime inference, which is the least supported. We are basically just making stuff up at this point. It is an extraordinary claim and thus would require extraordinary evidence to verify it.

Is it this evidence (two known dromaeosaurs with pedal integument, one with feathered feet and one with reticulae, while known basal avialans retain feathered toes) that NGMC 91 evolved its reticulae independently, or that Microraptor and some basal avialans evolved feathered toes independently? The plasticity of this feature in even crown birds makes bracketing this very problematic for very basal forms.

Yes, as I said it is possible that this feather suppression of the tarsometatarsus happened a few times. However this does not mean that because the tarsus was rescaled that we can infer this to other areas of dinosaur bodies since, again, we see no evidence of this in the extant realm. Should Dilong and Yutyrannus stay in Tyrannosauroidea (and should that clade ever receive strong statistical support) then I would say this would count as good evidence that tyrannosaurids re-evolved scales. It would appear to be the only option short of Dilong and Yutyrannus composing a close, but not directly related, clade to tyrannosaurids that evolved filaments convergently (still possible, but less parsimonious. Also this is assuming the filaments in those two taxa are homologous to protofeathers).

...looking at the modern developmental pathways of birds and crocs means that dinosaurs at some point in their evolution went from heat-to-toe scaly to head-to-toe feathered in a single evolutionary step with no partially-feathered intermediates. That's a rather large leap to take, especially since it assumes the developmental pathways for feather formation have gone unchanged for at least 165 million years, and that what we see in modern bird embryos is not the result of some kind of genetic "locking in" of an all or nothing pathway that developed in a stepwise or modular fashion.

Yes. This is the essence of the extant phylogenetic bracket. In this case I am making a level 1 prime inference. The pathway is seen in both crocs and birds, as well as lizards (Alibardi 1996) and possibly turtles (Alibardi & Thompson 1999). So it appears to be pretty darned conserved, yet it does not leave behind any osteological correlates. As for the phenotypic leap it is not as unexpected as you would think. We are talking about changes in regulatory genes here. These control dozens of other genes, so their effects will travel far and wide (e.g., prolonged activity of 5′HOXd expression in developing zebrafish result in reduction in fin tissue and the formation of cartilage reminiscent of the distal limbs in tetrapods [Freitas et al. 2012]. That's a small mutation making a big change). Again the fact that the scales in birds re-evolved through suppression of feather formation, and even the reticulae on the feet seem to have formed via similar suppression suggests that protofeathers evolved en masse and not in a stepwise fashion.

RE: Feathers and scales being found in conjunction.

Would you agree that such a find would falsify the evo/devo hypothesis? Even if we write the "scales" off as feather derivatives, their presence on parts of the body other than the feet and tarsus would show that changes have occurred in the developmental pathway between Ornithodira and Neornithes, since it is not possible to induce this kind of formation in modern birds.

Yes I would agree with that. This would be the kind of evidence needed to back up inferences of dinosaur integumentary development being unique to dinosaurs.

Refs:

Alibardi, L. 1996. Scale Morphogenesis During Embryonic Development in the Lizard Anolis lineatopus. J. Anat. 188:713–725.

Alibardi, L., Thompson, M.B. 1999. Epidermal Differentiation During Carapace and Plastron Formation in the Embryonic Turtle Emydura macquarii. J. Anat. 194:531–545.

Freitas, R., Gomez-Marin, C., Wilson, J.M., Casares, F., Gomes-Skarmeta, J.L. 2012. Hoxd13 Contribution to the Evolution of Vertebrate Appendages. Dev. Cell. 23:1219–1229.

[stoneage]

Is this thread locked, and if so why?

[tyrantqueen]

Is this thread locked, and if so why?

Erm...if the thread was locked, how would you be posting a reply on it?

[stoneage]

Is this thread locked, and if so why?

Erm...if the thread was locked, how would you be posting a reply on it?

Well, what does the X and lock under mark read  column mean?

[tyrantqueen]

Is this thread locked, and if so why?

Erm...if the thread was locked, how would you be posting a reply on it?

Well, what does the X and lock under mark read  column mean?

It means that since you authored (started) this topic, you have the option of deleting it. It has nothing to do with the topic being locked.

[stoneage]

Is this thread locked, and if so why?

Erm...if the thread was locked, how would you be posting a reply on it?

Well, what does the X and lock under mark read  column mean?

It means that since you authored (started) this topic, you have the option of deleting it. It has nothing to do with the topic being locked.

Okay thanks.  Last time I was on here I remember you couldn't delete anything.