National Geographic

Feathers for Tyrannosaurs

Feathery dinosaurs can be an acquired taste. Not everyone likes seeing animals that have traditionally been wrapped in scales begin to sprout brightly-colored plumage, especially when such changes threaten to dispel the menacing appearance of Hollywood dinosaur villains like Jurassic Park‘s Velociraptor. Of course, alterations to some dinosaurs raise the dander of fossil aficionados more than others. A fluffy Siats will stir debate among experts, but, simply by dint of the dinosaur’s celebrity, the prospect of a fuzzy tyrannosaur is a pop culture flashpoint in the tussle between dinosaurs of our childhood and the animals science is uncovering.

The impending release of Walking With Dinosaurs 3D has put tyrannosaur feathers on my mind again. The Land Before Time it ain’t, but the gorgeously-rendered animated film will undoubtedly excite the latest generation of young dinosaur fans. That’s why many paleontologists and dinosaur fans are disappointed that CGI docudrama’s villains, a gaggle of iridescent Gorgosaurus, are devoid of any fluff or fuzz.

In the grand scheme of the tyrannosaur family tree, Gorgosaurus was a large, sleek, and agile member of a subgroup called tyrannosaurids. This is the category of the most famous tyrant dinosaurs, including Tyrannosaurus itself. Yet we know relatively little about what the outside of these dinosaurs looked like. There are some rumored skin impressions – some lost, others frustratingly unpublished – that show tyrannosaurids had pebbly scales, at the very least. Befitting the traditional view of dinosaurs as scabrous reptiles, the filmmakers decided to go the conservative route and revive Gorgosaurus sans fluff.

Body size has played into the argument for scaly tyrannosaurids, too. If a 30 foot long, two ton plus Gorgosaurus had an active, hot-running metabolism, then wouldn’t an insulating coat of fluff cause the predator to overheat? Scale supporters could concede that small tyrannosaurs, and maybe even tyrannosaurid chicks, had fluff, but the prospect of a heat-addled Tyrannosaurus has helped keep large tyrannosaurs scaly.

Enter Yutyrannus. Not long after the Walking With Dinosaurs 3D settled on their scaly Gorgosaurus, paleontologist Xu Xing and colleagues described a roughly 30 foot long, one and a half ton tyrannosauroid that wore an expansive coat of protofeathers. Yutyrannus, along with some experimental work on how large animals shed body heat, suggest that body size was not a barrier to being a fluffy dinosaur.

Yutyrannus was described too late to change the look of Hollywood’s latest take on Gorgosaurus. And fans of the scaly-skinned model are often quick to point out a relational barrier between the two dinosaurs. The 125 million year old Yutyrannus was an archaic from categorized as a tyrannosauroid, while Gorgosaurus was a later and more derived member within the tyrannosaurid subgroup. Since the only tyrannosaurs so far discovered with protofeathers are the tyrannosauroids Yutyrannus and the comparatively tiny Dilong, and tyrannosaurids only left behind scaly skin, then maybe tyrannosaurs shed their simple plumage over evolutionary time.

A very elegant Tyrannosaurus. Art by John Conway.

A very elegant Tyrannosaurus. Art by John Conway.

But this doesn’t mean that a scaly Gorgosaurus – or Tyrannosaurus, for that matter – can be taken as a default position. I can only speak for myself, but I think it’s only a matter of time before someone publishes on a tyrannosaurid with protofeathers. And even if I turn out to be wrong, the way we currently envision these dinosaurs is open to multiple hypotheses that remain open.

Perhaps Gorgosaurus and other tyrannosaurids really were scaly, scaly, scaly with not a tuft of fluff to be seen. But the fact of the matter is that the smattering of tyrannosaurid skin impressions so far discovered doesn’t seal the case. The unpublished traces do not provide a complete record of tyrannosaurid body coverings. Tatters and segments are all that exist and have not necessarily been preserved in their natural position.

Nor does a patch of skin automatically mean that the entire animal was covered in only that sort of integument. (The same, of course, goes for feathers and their forerunners.) Beyond the many avian dinosaurs that have scaly legs in addition to feathery bodies, fossils of non-avian dinosaurs such as the little theropod Juravenator and the very distantly-related ceratopsian Psittacosaurus have demonstrated how scales and feather-like integument can simultaneously exist on the same animal. Dinosaurs didn’t always have a full downy coat – patches of protofeathers could have been useful for display and even touch. Silly as such speculation may seem, perhaps Gorgosaurus had long, simple protofeathers that could have acted like a cat’s whiskers as the carnivore tried to nab small prey. Or maybe the dinosaur had prominent fuzz along its tail which changed as the dinosaur matured. A covering of protofeathers need not be an all or nothing possibility.

A feathery Gorgosaurus. Art by John Conway.

A feathery Gorgosaurus. Art by John Conway.

And what of the chance that Gorgosaurus truly was as fuzzy as the documentary March of the Dinosaurs made it look? The discovery of scale impressions doesn’t necessarily preclude the possibility that tyrannosaurids had feathers. Feathery, non-avian dinosaurs are often found in fine-grained sediments where feathers have a better chance of being preserved. Large tyrannosaurids are not typically found in the same sorts of high-resolution geological settings, and so scraps of tough skin have a better change of being preserved than feathers. Some experimental studies of how modern birds decay and become preserved may help researchers better understand what happens to dinosaur feathers after death and their likelihood of being preserved.

Then again, traces of feathers can turn up in unexpected places. Last year paleontologist Darla Zelenitsky and coauthors reported on the remains of feathers around the skeleton of a young Ornithomimus – an “ostrich mimic” dinosaur that lived about 72 million years ago in prehistoric Alberta. No one had expected to find bits of dinofuzz among the relatively coarse grains of sandstone the dinosaur was embedded in, yet there they were. Who knows how many researchers, field volunteers, and lab prep experts have missed such traces because they didn’t think to look or accidentally appraised fossil protofeathers as plant traces?

The fuzzy Ornithomimus was found in the Horseshoe Canyon Formation. Skeletons of Albertosaurus, a close relative of Gorgosaurus, are found in the same formation. Perhaps there’s an Albertosaurus – already discovered or waiting to be found – that has survived the caprices of geological transformation with some remnant of feathers intact. Not to mention skeletons of tyrannosaurids found elsewhere.

What did Gorgosaurus look like in life? No one has a complete picture. Maybe a spate of future discoveries will show how tyrannosaurs gradually lost feathery body coverings as they evolved. Then again, tyrannosaurids may have borne anything from a few feathery tufts to decadent coverings of fuzz. The dinosaur’s appearance is open to multiple hypotheses. Scales-only cannot be taken as the default any more than totally-feathery tyrannosaurids can. But given how the story of dinosaur feathers has unfolded, I’d bet on the fuzz.

Paleontologists described the first non-avian dinosaur with protofeathers, Sinosauropteryx, in 1996. That was less than two decades ago. Experts are still discovering new types of dinosaur body coverings on an unexpected array of animals. Consider how much has changed and how quickly. Thirty years ago, depictions of feathery non-avian dinosaurs were thought to be reaching beyond the available fossil evidence. By fifteen years ago, feathers and their precusors were thought only to be present in the dinosaurs closely related to birds. Now fluff, fuzz, bristles, and similar structures are popping up all over the dinosaur family tree discovery-by-discovery. Either such body coverings evolved multiple times, or they were a common trait that goes back all the way to the last common ancestor of all dinosaurs.

I’m in no rush to call this debate. But we shouldn’t be too quick to roll our eyes at depictions of fuzzy tyrannosaurids or even illustrations as heretical as sauropods with some kind of protofeather equivalent. Scaly skin certainly has tradition on its side, but tradition is not the arbiter of accuracy.

Paleontologists started looking for non-avian dinosaur fluff such a short time ago that there’s far more left to be discovered than has yet been found, ranging from which dinosaurs had protofeathers to the function and even preservation of these beautiful body coverings. Since there are two fuzzy tyrannosauroids, and this lineage fits into a bigger group called coelurosaurs in which protofeathers have been found in every single lineage, I’d find it quite strange if big tyrannosaurids shed their feathery inheritance and fit the classic, scaly vision that has enthralled dinosaur fans for so long. The definitive evidence – one way or another – has yet to be uncovered.

Edmontosaurus regalis, with its cock's comb. Credit: J. Csotonyi

Edmontosaurus just got a silly crest. Could some sort of protofeather be next?  Art by Julius Csotonyi

The transmutation of dinosaurs is not complete. Even familiar creatures can change with the publication of a paper. Just last week a study by Phil Bell and colleagues proposed that the long-known, shovel-beaked hadrosaur Edmontosaurus sported a soft-tissue beanie that puts the herbviore in the running for the most ridiculous dinosaur of all time. This tweak is just the latest representation of how dinosaurs are changing. Tyrannosaurids will not be exempt from the ongoing push of what Thomas Holtz, Jr. has called the Dinosaur Enlightenment.

I don’t wish to diminish the joy some viewers will feel at seeing scaly, scary Gorgosaurus at the theater next weekend. A pebbly-skinned Gorgosaurus is reasonable for now, although not playing to my personal paleontological preference. But even if evidence lets Gorgosaurus keep their naked hides I have no doubt that new finds will alter our expectations about what these dinosaurs looked like and how they behaved. That’s wonderful. Paleontology is a science of change, both of life through time and our understanding of that long-lost nature. Even extinct dinosaurs will evolve in our imaginations. I can’t wait to see what changes next.

[Top image by John Conway. See his website for additional feathery dinosaur awesomeness.]

There are 49 Comments. Add Yours.

  1. Tomozaurus
    December 16, 2013

    “…tradition is not the arbiter of accuracy.”

    This point is an understatement. Tradition means literally nothing.

  2. Ethan Cowgill
    December 16, 2013

    Personally, I think that anyone illustrating any kind of coelurosaur without feathers is just fooling themselves. Luis V. Rey has made the change to fuzzy Tyrannosaurs. So has John Conway, and many others. Thomas Carr has said that anyone restoring Tyrannosaurids with feathers is un justified in doing at this time. Yet, he and Darren Naish suggest that Yutyrannus is actually a Charcarodontosaur in Tyrannosaur’s clothing. The carcharodontosaurs are more distant to birds than Tyrannosaurs are, and if they have feathers, if makes it all the more likely that Tyrannosaurs did too! At this point, I think it is just the people who don’t want their childhood monsters to change that are resisting fluff. They don’t want to lose their favorite scaled beast. Feathers make them seem all too real, all too familiar. We need to see these animals for what they really are. We need to change our way of thinking and include all possibilities. If Tyrannosaurs were scaly, I want to know, if not, I want to see. The truth matters more than 20th century preconceptions. We need to (as you said) “stare nature in the mouth” or in this case, the hide.

  3. Jura
    December 16, 2013

    Argh, scaly skin doesn’t have tradition on its side. It has the data on its side. Every case for filamentous integument (I appreciate you choosing fuzz over the overuse of “feathers” for filamented dinosaurs) in tyrannosaurs has been based on an overreach of the data. We have actual skin impressions from Tarbosaurus, Gorgosaurus, Albertosaurus and Tyrannosaurus. Let’s let the fossils do the talking instead of making up fancy interpretations based on a recent bias in paleo art.

    Thirty years ago, depictions of feathery non-avian dinosaurs were thought to be reaching beyond the available fossil evidence.

    They were reaching beyond the available evidence. Criticizing those interpretations was the correct approach as it was being conservative and scientific. The All Yesterdays movement may be right in that our overly conservative views of dinosaurs are likely to be wrong, but giving a greenlight to rampant speculation (which—despite the official statement of the authors—is exactly what it has done) only serves to undermine the science of paleontology.

    Also, it would be good to let your readers know that the alleged filaments on non-coelurosaurs are questionably homologous (the “quills” on that one Psittacosaurus differ markedly from the “quills” on Tianyulong, which both differ markedly from the protofeathers of coelurosaurs). There is a paper in the pipeline that should help settle some of these homology issues.

  4. Ethan Cowgill
    December 16, 2013

    @jura The only skin impressions from. T-rex are from a BHI specimen named “Wyrex” only a tiny tiny patch is preserved, and we have no idea where it came from. It doesn’t mean no feathers. Can I have a source please for the “We have actual skin impressions from Tarbosaurus, Gorgosaurus, Albertosaurus and Tyrannosaurus.”

    • Jura
      December 16, 2013

      @Ethan — I don’t find the “we have X impressions from Y area” argument a very compelling one. One could use that same argument to push in favour of scaly Deinonychus (no integument impressions so it must be up for grabs). We might not have many skin impressions for tyrannosaurs or other dinosaurs, but insisting that anything short of a full scale mummy is asking for too much. It’s the same logic that has been used to create purple and turquoise dinosaurs in the past. We can look at extant integument distributions and their evo-devo to get an idea of what is possible in extinct animals. Doing so for Deinonychus would produce a protofeathered animal based on bracketing from all sides by other protofeathered critters. Tyrannosaurs are not as well nested. More importantly we have physical evidence of what was on their hide. This evidence comes from the thigh (I think, based on Wyrex) and thoracic cavity (you wanted a reference: Currie et al. 2003). We don’t have any preserved filaments with any tyrannosaurid. Therefore the conservative approach would be to only restore scales on the animal. Doing otherwise is just as misguided as giving Sinosauropteryx a scaly body with a filamented mohawk (NGMC 91 ["Dave"] showed that filaments should go everywhere but the tarsometatarsus, whereas Microraptor showed that more basal dromaeosaurs wouldn’t even have scales there).

  5. Jura
    December 16, 2013

    Oops, and the full reference: Currie, P.J., Badamgarav, D., Koppelhus, E.B. 2003. The First Late Cretaceous Footprints from the Nemegt Locality in the Gobi of Mongolia. Ichnos. 10:1–12.

  6. Brian Switek
    December 16, 2013

    Jura:

    The presence of skin impressions does not automatically mean that the dinosaur in question *only* had scaly skin. As I mentioned in the post, there are dinosaurs that preserve both scales and integument (fuzz, bristles, etc.).

    Given that tyrannosaurid skin impressions have not yet been published I obviously can’t say much about taphonomy. But can we be so confident that skin impressions automatically rule out protofeathers or similar structures? Is it not possible that, especially in depositional environments with coarser grain size, skin impressions might be preserved but not other integument? Or that protofeathers might be lost sometime between death and burial but not skin? The details of where and why protofeathers are preserved, versus the taphonomy of skin impressions, might help strengthen one side of the case versus another.

    And on top of that, if tyrannosaurids only had scales then the evolutionary loss of integument has to be accounted for. As yet, the fossils showing that change have not been found. If protofeathers are a tyrannosauroid trait, then why rule out the characteristic of more derived members of the same group? Again, the presence of scales in tyrannosaurids does not automatically rule out other integument.

    As for my “Thirty years ago…” statement, I used that to show how quickly the field has changed, particularly as a sign of ongoing change. And I do not share your view that the All Yesterdays movement has undermined paleontology. Each piece of paleoart stands by its own merits and some illustrations are better than others, but every piece of artwork is speculative to some degree. To my mind, an illustration of a Gorgosaurus that is totally scaly is just as speculative as a feathery one. Conservative is not always correct.

    • Jura
      December 16, 2013

      @Brian — Tyrannosaurid skin impressions have been published (see Currie et al. 2003) albeit not that well described. Tyrannosaurus impressions are currently undescribed but we can at least say something about its close relatives.

      As I mentioned in the post, there are dinosaurs that preserve both scales and integument (fuzz, bristles, etc.).

      There are dinosaurs that are alleged to do that, but they (all two of them) are all contentious. The singular Psittacosaurus specimen might preserved quills, elongate scales or even something unrelated from the environment (e.g., plant parts, parasites). The only published data on the specimen is a short blurb that revealed very little of the morphology and none of the ultrastructure. Its status as a poached specimen has, unfortunately, made it a bit of a pariah for anyone hoping to do follow-up studies. As for Juravenator, it’s pertinent to point out that Chiappe and Göhlich’s interpretations are based on a specimen viewed under high magnification and under UV light. Even then the alleged filaments came off as extremely thin. They might be related to the integument, they might be deep to the integument or they might just be preparator scratch marks. In all these cases they don’t make for strong examples of mixed integument.

      The only indisputable mixed integument specimen we have is the NGMC 91 dromaeosaur. Even then the presence of scales was only on the tarsometatarsus and foot. This placement is on par with the only place we see scales in birds, and agrees well with a suite of evo-devo studies showing that scales and feathers do not intermingle (e.g., Sawyer & Knapp 2003 and Dhouailly 2009).

      if tyrannosaurids only had scales then the evolutionary loss of integument has to be accounted for.

      I wholeheartedly agree. If Dilong and Yutyrannus wind up staying in Tyrannosauroidea (and Tyrannosauroidea winds up getting actual statistical support in these trees) then we have a case where one form of integument was lost (filament) and replaced/re-evolved with another one (scales). It would suggest that scales offered a more advantageous integument for large tyrannosaurids for some reason. This could lead to studies on the function of scales (a remarkably understudied area of research). Large size would be unlikely not only due to Yutyrannus (which one should note, had filaments all over the body and not localized to any one region), but also because the animal could just have had naked skin instead, much like ostrich thighs and some vulture necks.

      Conservative is not always correct.

      I agree. In fact it is probably rarely correct as it tends to downplay the potential of the animals being reconstructed. However conservative interpretations do force us to stay within the limits of the data. They reign in speculation and force us to admit that there is only so much we know about something. That’s why conservative interpretations make for good science.

      Obviously applying this to all paleo art would be a bad idea since art is not bound by reality (e.g., Escher or Salvador Dali). One is allowed to speculate all one wants with most art. However if we are going to argue for scientific reconstructions then it’s best to keep things conservative since each step beyond the data is another speculation/hypothesis. We should reduce those steps as much as we can.

  7. Ethan Cowgill
    December 16, 2013

    @Brian Well done sir. @Jura I wasn’t using skin impressions for evidence of scaly Tyrannosaurs. I was simply saying that just because we have some scales from some part of T-rex doesn’t mean it didn’t have feathers. This is exactly what Brian said in the post and his comment. Did you find the Yutytannus claim I made in my first comment convincing at all? Thanks for the sources, I’ll get on reading those.

  8. Ethan Cowgill
    December 16, 2013

    @Jura come on, that paper you referenced me wasn’t relevant. The paper is about Nemegt footprints. You’re saying that because Tyrannosaurs had scaly feet they were completely naked? I dare anyone reading this to find me a single species of bird that doesn’t have scaly legs and at the very least feet. I don’t think anyone was expecting Tyrannosaurs to have the bottoms of their feet feathered.

  9. Jura
    December 16, 2013

    @Ethan — Check the paper again. They do talk about the bottom of the feet, but they also talk about impressions found around the thorax and how they agree with other impressions from other tyrannosaurids from Alberta.

  10. Jura
    December 16, 2013

    Argh, and I forgot to post the full references again. Regarding Evo-Devo:

    Sawyer, R.H., Knapp, L.W. 2003. Avian Skin Development and the Evolutionary Origin of Feathers. J.Exp.Zool.(Mol.Dev.Evol) Vol.298B:57-72

    Dhouailly, D. 2009. A New Scenario for the Evolutionary Origin of Hair, Feather, and Avian Scales. J.Anat. Vol.214:587-606

  11. Tomozaurus
    December 16, 2013

    The argument against scales and feathers coexisting is utterly ridiculous. You can hand wave Juravenator and Psittacosaurus all you want, but they still exist, and you haven’t even mentioned Scansoriopteryx. Regardless, there is a specimen soon to be published that very _clearly_ (I’ve seem photos of it) has feathers on it’s torso but scales including scutes on it’s tail and it’s legs.

  12. Raptormimus
    December 16, 2013

    Jura, I should probably note that plenty of large birds (elephant birds, cassowary, emu, moa, etc) get or have gotten along fine in tropical climates with very long feathers (hell, cassowaries are _black_, the most heat-absorbing colour, with very long feathers), so the arguement of overheating is kind of moot.

  13. Andrea Cau
    December 17, 2013

    Different fossils of the same species may result very different due to different depositional conditions. Thus, we have to avoid literal interpretation of the preservation in a fossil to negate some tegument.
    For example, we have some troodontids under volcanic ashes from the Early Cretaceous of China, and morphologically very similar (if not identical) troodontids from lacustrine beds from the Early Cretaceous of China. The former are as 3D fossils lacking feathers, the latter are as 2D fossils with feathers. Hope nobody concludes that there were two kinds of troodontids: the scaly ones and the fluffy ones.
    The comprognathid Scipyonyx has an extraordinary preservation of its intestines, but no preservation of the skin. The compsognathid Sinosauropteryx has an extraordinary preservation of its skin, but no preservation of intestines. Hope nobody concludes that the former lacked skin and the latter lacked intestines…
    Thus, it seems to me that the difference in tegument preservation between some Late Cretaceous tyrannosauroid (e.g., Gorgosaurus) and some Early Cretaceous tyrannosauroid (e.g., Yutyrannus) cannot be taken as a literal evidence of skin difference. Tyrannosaurids are deeply bracketed by both fuzzy and scaly dinosaurs, thus, the best interpretation is to depict them with both teguments.

  14. Max
    December 17, 2013

    I must admit, after initial resistance, I am becoming increasingly won over by dinosaur fuzz, and increasingly disappointed at its absence. We live in interesting times.

    But Brian, surely Ornithomimus is a bird mimic? It’s Struthiomimus that is more specifically the ostrich mimic.

  15. Tomozaurus
    December 17, 2013

    A further note: I read the Currie reference on the Tarbosaurus skin impression linked in a previous post (thanks for that by the way, I’d heard about it but didn’t know where the reference was from).

    The impression is 2×3 cm and shows small rounded bumps. It was found by the thoractic region but apart from the skeleton and impossible to know where it came from on a disassociated carcass that had been trampled by hadrosaurs(!). There is too many variables there to say this impression tells us much of anything.

  16. Liz
    December 17, 2013

    The feathers aren’t just for warmth. Feathers would make dinosaurs more aerodynamic, allowing them to run faster and aiding them in jumping on prey. Feathers also allow an animal to have optional warmth. A bird puffs up to warm up in cold weather. To air out and cool off in hot weather, a bird’s feathers are flat with wings out.

  17. Matt Martyniuk
    December 17, 2013

    Jura: you frequently cite the evo/devo studies and I have to admit i’m almost 100% ignorant of that science. Can you explain in layman’s terms what evidence suggests the pattern seen in modern birds (mutually exclusive development of scales vs. feathers on various parts of the body) arose in a single evolutionary step? How do we conclude that the modern evo/devo pattern did not at some point in evolutionary history of the bird lineage arise from a more complex or more mixed integument development pattern?

    In other words, even if this is true for modern birds, how can we possibly know it the exact same developmental pathway evolved fully formed in early Jurassic dinosaurs and has remained unchanged since? This almost sounds like an argument for irreducible complexity, or saying that developmental pathways do not evolve. This strikes me as bizarre, but, again, not familiar with the field.

  18. Matt Martyniuk
    December 17, 2013

    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. I suspect evo/devo proponents will move the goalposts and say that the tail counts as a different segment, as the feet do in modern birds. 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?

    • Jura
      December 18, 2013

      @Matt — I wrote about much of this on my site a while back (which, judging by your September blog post, you read :)).

      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.

  19. Tomozaurus
    December 17, 2013

    If the goal-posts were to be moved to allow the tail as a separate segment (which thanks to Concavenator and the unpublished ornithschian I already consider to be the most likely scenario) this would essentially kill the “tyrannosaurids must be entirely scaly” argument outright as all associated skin from tyrannosaurids comes from the tail.

  20. Ian
    December 17, 2013

    I’ve never seen the Tyrannosaurus skin impression, so I may be totally wrong here, but is it possible that Tyrannosaurus skin appeared scaly while lacking true scales? I’m thinking of opossum tails, beaver tails, armadillo skin, and the pebbly skin of indian rhinos. Maybe Tyrannosaurids evolved from fuzz covered ancestors, lost some of that fuzz and their bare skin took on a scaly appearance.

    Ostrich legs and vulture necks might not be a good analogue. Don’t T-rex skeletons show that they sustained a lot of injuries? Maybe they had a tough, pebbly rhino-like hide.

  21. Phil Anselmo
    December 17, 2013

    Are the filamentous integument founded on dinosaur fossils are indeed, feathers?

  22. Jason S.
    December 17, 2013

    Integument distribution is not necessarily a phylogenetically coded trait in many endothermic megafauna, and can vary from species to species. For example, the thickness of hair layers in “pachyderm” megamammals (elephants and rhinoceroses) generally follows a latitudinal gradient, with cold-adapted polar species having longer, more concentrated hair follicles than their tropical-dwelling relatives. The same rule may have applied to the large theropod dinosaurs of the Mesozoic, including the tyrannosaurs. Under this assumption, cold-adapted tyrannosaurs such as Yutyrannus and the North-Slope gorgosaurs would needed thick coasts of protofeathers more so than similar-sized tyrannosaurs living in tropical and temperate environments (e.g. Hell Creek, the Nemegt Basin, the Wangshi Group, etc.), which would have had significantly sparser and finer integument. Of course, it is still possible that adult specimens of the largest tyrannosaur species did indeed have superfluous protofeathers for insulation and visual display.

  23. Sparticus
    December 17, 2013

    I’m guessing the amounts of feathers a larger theropod had depended largely on where they lived. Warmer climate had less feathering (probably just some ornamental feathers on the head, arms and tail, with maybe some light feathers along the body not unlike the hair of an elephant), but in colder climates they were completely fuzzy. So, hell, an individual from the lower 48 might be nearly featherless, but an individual from northern Canada might look like some sort of nightmare snowy owl!

    We’re also not even taking seasonality into account here; a LOT of animals go through a molt in the spring, it’s entirely possible that dinosaurs did the same, and spent part of the year scaly, and part of the year fuzzy.

  24. Jonny O
    December 18, 2013

    Okay – let’s talk birds vs theropods. Birds preen endlessly because of the nature of their feathers (in most avian lines, feathers are required for flight), making use of an oil (sebaceous) gland at the base of their (feathered) tail. This oil helps maintain feathers – and it is applied via the use of a bird’s beak (and made possible because of the highly-flexible neck of neornithines). Did dinosaurs preen? If so, did dinosaurs have an oil gland at the base of their tails? Dinosaurs had limbs not wings – so, if they preened, did they do so via the use of their phalanges? Certainly their necks were not as flexible as today’s birds. Everybody always ignores these details.

  25. Matt Martyniuk
    December 18, 2013

    ” This is further bolstered by the fact that reticulate “scales” in birds appear to actually be highly suppressed feather buds (Dhouailly 2009).”

    I am familiar with this bit having recently blogged about it. The trick is that afaik reticulate “scales” are not found in crocodilians. However, 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. How do we know these “scales” are not also highly suppressed feather buds? 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?

    Note also that you cite Microraptor as evidence for a head-to-toe feathering as the ancestral avian condition (or at least AN ancestral condition), and NGMC 91 as evidence that by this point feathers were suppressed. Anchiornis, Sapeornis and Xiaotingia also have feathered tarsals and feet (as do some modern birds). 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.

  26. Matt Martyniuk
    December 18, 2013

    “I’m not proposing that feathers magically appeared”

    No, just that 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.

  27. Matt Martyniuk
    December 18, 2013

    “First, much has been made of Godefroit’s specimen despite it not being published.”

    Agreed, and I’m as guilty of that as anyone, but that’s why I posed it as a hypothetical. Let’s say a specimen of any stem-bird taxon were found with unquestionable feathers (branched filamentous integument with a rachis and barbs) on one part of the body and scutellate, reticulate, or otherwise “scaly” integument on another part of the body other than the feet or tarsus.

    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.

  28. Andrea Cau
    December 19, 2013

    The difference between NGMC 91 and other microraptorians may be taphonomy-biased. Someone should study the distribution of tegument among all the dinosaurs in a systematic way, integrating phylogeny, tegument ontogeny AND sedimentology and taphonomy, even including experiments on actual bird and reptile bodies to see what happens to their skins under different post-mortem conditions.

    “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.”

    If such pattern reflects (at least in part) the bird lineage evolution, we may predict some basal dinosaurs far from birds with filaments on head, back, tail and torso an the rest of the body lacking filaments, then dinosaurs closer to modern birds with a more extensive covering of feathers but no tarsal scutes, and then dinosaurs even closer to modern birds with tarsal scutes. This is what the fossil record actually shows: Psittacosaurus has quills on back but scales elsewhere, maniraptorans shows a fully feather covering but no tarsal scutes, and ornithuromorphs show tarsal scutes.

  29. Jura
    December 20, 2013

    …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.

  30. Jura
    December 20, 2013

    @Andrea — If such pattern reflects (at least in part) the bird lineage evolution, we may predict some basal dinosaurs far from birds with filaments on head, back, tail and torso an the rest of the body lacking filaments, then dinosaurs closer to modern birds with a more extensive covering of feathers but no tarsal scutes, and then dinosaurs even closer to modern birds with tarsal scutes. This is what the fossil record actually shows: Psittacosaurus has quills on back but scales elsewhere, maniraptorans shows a fully feather covering but no tarsal scutes, and ornithuromorphs show tarsal scutes.

    This initial step (Psittacosaurus) is highly dependent on the “quills” being 1) a real part of the animal (they appear to go behind the specimen rather than into the skin) and 2) homologous to what we see in maniraptorans. This seems doubtful given a superficial analysis of the structures. There is an upcoming paper that casts doubt on its secondary homology too.

  31. Matt Martyniuk
    December 20, 2013

    @Andrea: Yes, taphonomy probably has at least something to do with what we see on paravian feet. NGMC 91 preserves reticulae on the feet but does not show what integument was present on the rest of the metatarsus. Sapeornis is porbably informative here–the tail-feather specimen shows feathered toes and ALSO reticulae on the underside of the feet/foot pads, which makes sense. This might be the situation in NGMC 91, except the foot and tarsal feathers were not preserved, and in Microraptor, where the foot pads were not preserved.

    Doesn’t Concavenator preserve tarsal scutes? This came up in comments on my tarsal scute blog post. Saurolophus is reported to *lack* tarsal scutes. How about Psittacosaurus? Godefroit’s specimen is rumored to also have tarsal scutes. If all of these tarsal scutes are homologous, and developmental studies are correct that tarsal scutes are derived from feathers, feathers must be basal to at least Avetheropoda, given Concavenator.

    Note that Andrea’s scenario is also supported by interpretations of feathered Juravenator–dorsal feathers, scales on the leg and underside of the tail. The leg and underside of the tail also happen to be (frustratingly) the only skin impressions from Concavenator.

  32. Andrea Cau
    December 20, 2013

    @Jura: “they appear to go behind the specimen rather than into the skin”.

    I have good photos of the specimen, showing the quills penetrating the skin and reaching the dorsal apex of the neural spines. It is clearly visible in the anteriormost quills. This support the hypothesis that they were inserted along the dorsal surface of the tail. Thus, I see no reason to consider them as something distinct from the animal.

    • Jura
      December 20, 2013

      @Andrea — Looking at the pretty detailed photos on Dave Hone’s blog, I don’t see any sign of these structures coming near the neural spines. I’d love to see higher resolution photos of the real specimen if you have them available (and are able to share them).

  33. Jura
    December 20, 2013

    @Matt — If all of these tarsal scutes are homologous, and developmental studies are correct that tarsal scutes are derived from feathers, feathers must be basal to at least Avetheropoda, given Concavenator.

    Tarsal scutes are not unique to birds though. Crocs, tortoises and other reptiles have them too. As we have gone back and forth with on this thread, scales (including scutes) on the tarsals and feet are ambiguous indicators of integumentary covering because of this developmental relationship.

  34. Matt Martyniuk
    December 20, 2013

    @Jura Really? I didn’t know that! Which tortoises and crocs have bird-like tarsal scutes? Most photos I’m finding show broad scales on the tarsus, but these don’t really resemble the ones in birds. They’re generally small and segmented around the whole foot and leg and grade into the polygonal scales on the leg and underside of the foot. Tarsal scutes in birds are generally unsegmented longitudinally and span the whole tarsus as one continuous scute, bordered by reticulae with little grading. I’m under the impression those of Concavenator look like birds, but I don’t have the paper handy. If there are crocs or testudines with tarsal scutes similar to birds that would destroy the bracket. But if not, it is not at all parsimonious to presume croc/turtle-homologue tarsal scutes evolved a very bird-like morphology in Avetheropods, then were lost in favor of feathers, then re-evolved as feather-derived tarsal scutes with an identical morphology in euornithes.

  35. Brian Edwards
    December 20, 2013

    Is it possible that a plucked feathery integument could look like scales? I am thinking of ostrich leather accessories in asking this.

  36. Andrea Cau
    December 21, 2013

    @Jura: http://1.bp.blogspot.com/-MGjBVtHAY_o/UrVOJ1DxotI/AAAAAAAAFlk/KKtLzoMi_ps/s1600/Psittacosaurus.jpg

    Note that one quill (blue arrows) overlaps the apex of the neural spine, while the other (red arrows) is overlapped by the spine. This supports the interpretation of the quills as inserted along the dorsal surface of the body parasagittally to the vertebral column dorsal line.

  37. David Bump
    December 26, 2013

    What bothers me is the one-way psychology of the article, the quickness and strong assurance in assigning the portrayal of scaly tyrant lizards to little more than a matter of personal taste and stubborn conservatism, without word one about what is obviously a very strong desire on the part of many people to have feathers on anything that they can find any reason to do so.

    “But we shouldn’t be too quick to roll our eyes at depictions of fuzzy tyrannosaurids or even illustrations as heretical as sauropods with some kind of protofeather equivalent.” Ah yes? But what about the quickness to roll out an article whining about how dinosaurs, which MAY very well, for all we now know, have been entirely scaly, happen to be portrayed that way?

    “I don’t wish to diminish the joy some viewers will feel at seeing scaly, scary Gorgosaurus….” Perhaps not, but clearly you feel cheated out of the joy of seeing fuzzy, scary giant carnivores.

    I haven’t heard of anyone talk about the subject as if they felt any regret at the change from what they remember as a child, but every one of the original leading promoters of feathers and fuzziness who have spoken at any length on the subject has talked about the excitement of looking at birds and knowing that they are living dinosaurs; obviously every dinosaur that is portrayed as having feathers or feathery fluff contributes to the strength of this pleasant experience, which apparently those given to it feel an almost missionary-like desire to share. At least, that’s the impression I’m given by this urge to stomp out all portrayals of scales-only bipedal dinosaurs.

    Then, too, there are other considerations we could look at that don’t even enter into these discussions — while CG techniques have advanced a lot, it’s still probably easier (and cheaper) to have scaly dinos without fluff or tufts or anything like that. Plus by analogy we’re familiar with a number of large animals belonging to a fuzzy group (mammals) that don’t have any fuzz that you’d notice at a distance — modern elephants, rhinoceroses, and hippos. Until we have definite proof that large dinosaurs were visibly fluffy, the image might just be too jarring for a movie seeking to appeal to a general audience.

    If large dinos did have some fuzzy integument, it might not be noticeable. It might be that the scales were more prominent and you wouldn’t notice little dino-fuzz filaments between them. For that matter, if you were an alien and didn’t know about mammals and saw a picture of giraffes at a distance, could you be sure they were fuzzy? So if it makes you happy, you can watch the movie in the full assurance that there are little pinfeathers between those scales, but they’re just too small to show up. Yay!

  38. Jura
    December 28, 2013

    @Matt — You weren’t asking for bird-like tarsal scutes. You simply said tarsal scutes. Though even with that qualifier I’m not entirely sure much could be separated anyway. The scutes on the metatarsals and phalanges of alligators look awfully avian-like to me (http://upload.wikimedia.org/wikipedia/commons/1/17/Alligator_foot_detail.jpg). The biggest difference between croc scutes and bird scutes—anatomically—seems to be the amount of scutes on the metatarsus. However I suspect that this is largely due to the more compressed metatarsus of birds (essentially being one bone). Since theropods show a less pronounced compression in their metatarsus shape I wouldn’t be surprised if there was only single scute “shields” along the entire metatarsus, versus the individual scute “shields” we see on the more spread out metatarsi of crocs. As for the Ortega et al. article, they mention “polygonal scales” along the metatarsus, but don’t really define scutes on Concavenator.

  39. Jura
    December 28, 2013

    @Andrea — Thanks for the more detailed image. I agree that the structures appear to go behind the vertebra, but I don’t see a “quill” moving in front of it. That vertebral spine seems to be partially broken in that area (possibly a preparational accident). All the vertebrae in this region appear to be rising out of the rock whereas all the integument seems to be two-dimensional stains.

  40. Andrea Cau
    January 2, 2014

    @Jura: that few is what the photo shows. One quill overlaps a spine, other quills not. This is not a definitive evidence of a tegumentary origin, but at least is not even definitive that these features are not included in the body of the dinosaur. In short, be free to see what you want to see, as it seems to me that you already “know” what these features are.

    Pending a full description of the specimen (including its taphonomy, not just its anatomy), I’m open to every interpretation: the mere presence of a bizarre feature is meaningless if not integrated to an analysis of the geological conditions that produced that fossil. Thus, I don’t have a definitive idea on what these features are. Although they seem tegumentary structures, perhaps are not part of the body. Perhaps, the fossil is a fake. Until a careful look to the specimen, and not just to photos, I remain open to every conclusion.

    A comment to David Bump’s words.
    I’m interested to know what these fossils are and how they formed, not to defend a particular paleoartistic iconography due to some emotional feelings. For me, dinosaurs are not “cool” due to their “live appereance”, thus I’m not biased toward a particular tegument or another.
    Saying that Tyrannosaurus is “cooler” if feathered is as childish as saying that is “cooler” if scaly. Tyrannosaurus is not “cool”: it’s a paleontological hypothesis on a set of fossil data.
    This is why I usually remark the taphonomic aspect of all these discoveries, more than just the mention of a feature instead of another. Understanding why some fossil dinosaurs show particular tegumentary remains while others show different features, is for me much more interesting than just updating the “iconography” of the dinosaurs. I don’t care if a particular dinosaur was scaly or fuzzy or frilled or pink or spotted. I’m not interested to defend an old icon or a new trend. Paleontology is more than just updating the iconography of extinct animals. Most people perhaps have to stop thinking of dinosaurs as pictures, paintings, CGI images or illustrations. Perhaps it’s boring, but the only truth is: dinosaurs are pieces or rock.

    • David Bump
      January 2, 2014

      I hope you are the paragon of objective, disinterested research you describe yourself to be, Andrea, in which case you can apply the negative outcome of the old saying, “If the shoe fits, wear it.” There certainly are enough people who do fit my description, at least as many and as well as those described as being interested in the old iconography. Of course, those enamored of the new might object to your “dinosaurs are pieces of rock” instead of “dinosaurs are being chased away from my feeder by squirrels.”

  41. Marcos K. Pinheiro
    January 7, 2014

    All right everyone! Everyone has own opinions, reasons and imaginations. But still, there are some people and experts that depends more on evidence than imagination.

    http://www.nature.com/news/palaeontology-the-truth-about-t-rex-1.13988

    Like in this link, Thomas Carr is not convinced of fuzzy or fetheared T. rex. Well, I don’t know if he changed his mind afterwards. Still, we have to be patient and think what we think or maybe change our minds or not. And I, to be honest, I believe that T. rex were both scaly and fuzzy for now (well, more scaly than feathered). Because later discoveries have shown, like the MOR 1125’s soft tissue, that tyrannosaurs were more linked to birds, like chickens and ostriches, than reptiles, like crocodilians and lizards. But in th future, I’m aware that new discoveries will show that I was wrong. So we have to wait. And I love those Gorgosauruses that David Krentz have created for WWD 3D film, even without feathers. But since the discovery of Yutyrannus, now I believe that this species was scaly but fuzzier than T. rex because it lived much further North and was almost the same size as Yutyrannus. But…

    Who knows if Carr’s theory was right in the future? Who knows if some were feathered and some were not, like the Sumatran Rhino is hairier than the white and black rhinos? So I’ll pray and wish a lot that a “mummy” tyrannosaurid will be found and reveal its true skin to us all. Maybe Jack Horner or Phil Currie will find this amazing specimen.

    Oh! And I’m leaving for you all these links that I’ve found and maybe you’ve seen it or not, but just in case:

    http://blogs.discovermagazine.com/notrocketscience/2012/04/04/yutyrannus-a-giant-tyrannosaur-with-feathers/#.UswYibR8C2o

    http://z13.invisionfree.com/Hell_Creek/ar/t19.htm

    http://boards.straightdope.com/sdmb/showthread.php?t=647556

    • David Bump
      January 28, 2014

      @ Marcos:
      http://www.telegraph.co.uk/science/dinosaurs/9186922/Giant-feathered-dinosaur-Yutyrannus-discovered-in-China.html
      [Quote]

      “The feathers of Yutyrannus were simple filaments,” said Xu Xing, a legendary fossil hunter from Beijing’s Institute of Vertebrate Palaeontology and Palaeoanthropology.

      “They were more like the fuzzy down of a modern baby chick than the stiff plumes of an adult bird.”
      [End Quote]

      As we are unable to examine the pattern of growth and genetic basis of such filaments, how can we ever be really sure they’re not simply analogous structures?

  42. Neil
    January 14, 2014

    from a really curious layperson:
    1. If an animal’s ancestors are fully feathered, and through the course of evolution or merely adaptation, it lost its feathers – wouldn’t it just have smooth skin on the formerly feathered areas? Or can scutes/scales be redeveloped/redistributed throughout the body?
    2. Would the possibility of Yutyrannus falling outside the immediate tyrannosaur family tree be proof for (or against) feathers?

  43. Marcos K. Pinheiro
    January 28, 2014

    @ David Bump:
    Thanks for your comment David. Hum… A good question, but I don’t feel as the right person to answer that. And yet…

    http://www.telegraph.co.uk/science/dinosaurs/9186922/Giant-feathered-dinosaur-Yutyrannus-discovered-in-China.html

    And in this link, it has a quote saying:

    “Yutyrannus dramatically increases the size range of dinosaurs for which we have definite evidence of feathers,” Xu said.

    So it’s believed that those structures were indeed feathers or fuzz! I’ll keep believing for now that those filaments were indeed feathers.

    But patience, like the new babies of Chasmosaurus and Parasaurolophus reported in 2013 and the astonishing specimen of Edmontosaurus regalis with evidence of a comb on its head, we must root for a “mummy tyrannosaur (or T. rex at best)” to be found, studied and revealed to all the dino fans.

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