Wednesday, June 21, 2017

An Issue of Scale

Depending on how you deeply you read into the title of this post it can be not only a double but a triple entendre.

 "How many angels can dance on the head of a pin?"

Can be rephrased as "how many T. rex scales can fit on the head of a pin?"  That is the size of a millimeter and that is a little more than the average size of the T. rex "scale" documented in the recent Bell et al. (2017) paper that has got everyone flummoxed from here to kingdom come. Another visual is that more than 20 T. rex scales can be lined up across a penny. Take home point: these "scales" were small.



From Bell (2017) Note the scale bars in C & E are 5 mm while the scale bars in G & H are 10 mm.
These scales were minuscule!!


I think such dramatic issues of scale have been a bit washed over in the more hyperbolic proclamations  of the scale loyalists: "Yes, we have won!! Good riddance feather nazi elves!!" versus the recalcitrant permutations of the suddenly defensive feather crowd; "This tells us nothing new"; "Taphonomy washed away the feathers"; "Maybe T. rex had a feathered petty-coat?" Now I don't mean to mock such ideas and criticisms on the part of the pro-feather contingent but one can't deny there has been a palpable shift in sentiment from mainly feathered to mainly scaled in tyrant lizards (and by extension other largish theropods). Ironically many of the charges leveled at "awesomebros" or JP stylized scale loyalists are now being charged at the pro-feather faction; clinging to an ideal; putting an aesthetic before data; emotional attachment etc. etc.

Things are definitely a bit more unsettled and chaotic than many are comfortable with. Which is something I have been highlighting for some time in this blog; things are going to be getting more testy; a bit more non-consenus; a bit more uncomfortable for some time before things start to simmer down. Most of all things are going to be getting a bit weirder.

And those Wyrex scales are awfully weird. As I highlighted at the top of the post they are ridiculously small. Mark Witton called it the "Revenge of the Scaly Tyrannosaurus" in his blog post on the topic. If this is revenge via sub-millimetere "scales" it is perhaps the most underwhelming revenge story ever told. Sorry, I've had pimples bigger than those scales. I mean they are freaking small?! What is up with them? To put the size of these scales in perspective they are approximately equal to gila monster scales - komodo dragon scales would dwarf them. For all intents and purposes T. rex adorned in these minuscule scales would look pretty much nekkid. Especially so considering the absolute lack of any larger feature scales, larger keeled scales, osteoderms etc etc. Now, jokes about the puny size of T. rex scales aside, I do agree with Mark Witton on major points - and I'm glad he made this jump - that naked hided tyrannosaurids are not only a defensible option, but a likely one. He also raises the pertinent question - again something that I've been clamoring for here for a while - that many larger traditionally feathered dinosaurs may have lost significant amounts of fluff upon attaining larger size  (I do have some reservations on the osteological correlates for large facial scales that Mark seems to abide by but that is for another time). Another pertinent read is Andrea Cau's post on the subject. He makes some very valid and strong arguments, as he has for some time now, that taphonomy is key to a more detailed understanding of the nuances for feather, scale, "integument" preservation. Cau also raises issue with the strange shape and morphology of these scales - an observation I share and if you read the comments on his blog and know my history you can already probably guess where I am going in this piece … C-----A-----R-----U-----N------C…..

I don't know of any concrete studies linking scale size to body size but intuitively such a connection makes sense. I mean larger crocs have larger scales, larger monitor lizards have larger scales, larger boas have larger scales. That is just my off the cuff observations and I'm sure there are exceptions. But, generally speaking, scale size in a related group should get larger as the animals get larger both ontogenetically and in between related species. Did tyrant lizards break this pattern? Should smaller specimens have even smaller scales? Or are they all the same size regardless of size/species? The connection between scale size and body size both ontogenetically and between related species is probably a topic rife for potential studies.

*Turns out there are some studies linking scale size to body size. I went back and read the chapter of hadrosaur integument, authored by a certain guy named Bell, from the epic Hadrosaurs book from Indiana University Press and came across this gem which I will put here:

from A Review of Hadrosaurid Skin Impressions

"Scale morphology (especially scale counts) in modern squamates and crocodilians is typically conserved intraspecifically and is highly important in species identification (Spearman 1973; Brazitis, 1987; Hall, 1989; Cox et al., 1993; Charette, 1995; Branch, 1998). However, scale size (inferred by the inverse relation to number of scales) has been shown to vary positively with body size in some lizard species (e.g. Scleroporus, Ouferio et al., 2011). Similarly, body size (and hence, scale count) is variable both intra- and interspecifically among some squamates in relationship (both positive and negative) to Bergmann's Rule (i.e. body size decreases at lower latitudes or in warmer climates), which is correlated with minimum annual temperature and aridity (Sears and Angilleta, 2004; Oufiero et al., 2011). Despite these variations, scale morphology is one of the most reliable in the identification of extant squamates and crocodilians, especially in closely related species (Brazaitis, 1987; Charette, 1995). It is notable also that tarsal- and toe-scale patterns have been used successfully to identify individual species of extant avians, particularly raptors (Clark, 1972; Stauber, 1984, 1985; Palma, 1996)."

It is useful to note that the above paragraph is couched in a general discussion asking "can scales be used to identify individual hadrosaur species?". The promise for this sort of inquiry is great for hadrosaurs. For tyrannosaurids - as I will get into below - the promise for this sort of species identification based on scales is not looking as promising. But just for starters, who wants to venture a count on how many sub-millimeter sized scales covered a T. rex? What is the morphology of these scales? Any sort of repeating pattern? Architecture?

Are retro '90s Tyrannosaurs making a comeback? is a recent post by Paleo-King (Nima) on deviantart. While the general thrust of his piece is useful he makes a claim in the comments section that the various tyrannosaurid scale impressions are exactly the same as the well documented hadrosaur scales/mummifications. I do have to take issue with this comparison.

1) Extent of preservation. In hadrosaurids we have full on mummies that give us real life confident appraisals of where and how far scales occurred. So far in tryannosaurids we just have bits and pieces. Together these pieces suggest that "scaly" type integument is our most parsimonious appraisal for most of the body, if not all of it. But keep in mind that we as of yet don't have proof of "scaly" integument on the face and those persistent rumors of non-scaly neck displays in Tarbosaurus. Remember both crocs and birds have dispensed with scales on the face. Why? I'm not sure. It is interesting that both crocs and birds both have highly sensitive, tactile faces as well.

2) Size of scale and variety. While some hadrosaurs show scales on the millimeter range such as the Osborn "Trachodon Mummy" which are 1-5 mm and are described as "pavement scales" these patches of small scale are interspersed with regular patches of "feature scales" which are much larger at 5-10 mm.  What we see in terms of scale variety in tyrannosaurids so far is quite limited to very small "basement" type scales of a size smaller than in hadrosaurs. Hadrosaurs both at a distance and up close would have appeared much more textured than tyrannosaurids based on what we know so far. Unless you have some super X-men levels of visual acuity tyrant lizards would have looked basically nekkid.

3) Architecture. Nima points to an obvious architecture in the scales of tyrannosaurids. I have to admit that I can't see it. Carnotaurus shows architecture in the regularity of larger 4-5 cm tubercles arising every 10 cm or so from a more "basement" size scale of 5 mm tubercles. Sauropod and hadrosaur scales show a more obviously repeating scale architecture than tyrannosaurid tubercles. What I see in the tyranosaurid tubercles is something of a much more random, haphazard pattern. Apart from a size threshold of about 1 mm for the tubercles I can't discern any consistency in size; some appear more than twice as big as others and shape - apart from being generally polygonal there is a wide variety of shapes. Some of the tubercles appear rounder; others ovoid; some taper to a point; some wrap around others; and some almost to appear to bud off into other tubercles. This is a far cry from the more standardized scale pattern of hadrosaurs, which are often in repeated hexagonal patterns. Additionally given the 30 square cm patch of ilium scales we can be pretty confident that there was no larger patches of feature scales or repeating rows of larger keeled scales/osteoderms as in Carnotaurus, titanosaurs etc etc.

*Update. looks like a spoke too hastily, Nick Fonsesca says that Tarbosaurus has some feature scales form the supplementary info and then there is this from the paper:


Although I could not see the feature scales pictured in the supplementary there is indeed some evidence for a more orderly pattern of tubercles on some tyrannosaurid specimens, although not from the Wyrex material. It is of note that these feature scales are from the abdomen. Can they in fact reflect a more basal state retained? (i.e. never became completely feathered). Things are always aflux!!


So are 90's tyrannosaurs making a comeback? Sort of, I would say, but not exactly. The lack of discernible rows of feature scales or keeled scales is an obvious departure from GSP tyrannosaurids or any sort of organized row of larger scales so prominent in 90's style GSp tyrannosaurids.

And here I have to admit a weakness of not trusting my own gut and capitulating to the whole shaggy T. rex visage that has come into vogue in recent years. I blame Saurian. No, just kidding, I jest just a bit. Some have construed some of my posts as an attack on Saurian game design or that saurian should be changed or whatever. I can't disagree more. In fact I feel a bit sorry for the development team at Saurian, they must get pestered by young dino obsessives all the time. Just leave 'em alone at this point!! If Saurian is wrong fundamentally in some ways I think - at this point - these potential errors should be preserved for posterity. It's always interesting and iluminating to look back on paleoart to see how thought and ideas have changed. Saurian can be a great time capsule for what the general thought was of this period.

I do feel a bit of edification in getting back to my gut feeling for my latest tyrannosaurid art, in which I went with mainly nekkid skinned tyrant lizards with some manes and petty-coats of filaments. Proud to say this was completed before the new data came in. Boo - ya!! No need for revisions here, folks! Who says intuition, gut feelings, and following your muse have no place in science!! First published March 23, 2017 Gaslighting the Dinosaur: Just How Weird Can Dinosaurs Get?

Revelations by Duane Nash


Another argument that I would like to weigh in on is why Yutyrannus would go fully feathered while similarly sized northern tyrants like Albertosaurus went nekkid in a climate that was presumably not too different in temperature. Not to discount some of the other suggestions but merely augment, let's keep in mind that Yutyrannus was a normal slab chested theropod. Tyrannosaurids came wit da thikkness, they were barrel chested beefcakes, much more better heat retention in the torso. Big bois. Throw in some nice counter current heat exchange for the extremities, maybe a bit of a fat layer too, and you have a pretty good heat retaining system - much better than slimmer, earlier theropods at least. Perhaps a seasonal coat was a thing in northern variants, perhaps the young sported downy coat.

Back to the topic, again, my argument is not one of denying the overall message - that tyrannosaurids had a mainly "scaly" integument - but that the tyrannosaurid "scale" in both size, shape, architecture and pattern is quite distinct from those qualities of scales discerned in Carnotaurus, sauropods, and hadrosaurids. The differences in tyrannosaurid scales between these, presumably more basal integumentary patterns, very well might indicate secondarily derived "scale" patterns. In short that tyrannosaurids - like modern birds - had to reinvent the scale from a mainly feathered ancestral state.

This of course is not a novel concept, indeed the authors of the paper (Bell et al. 2017) seem to lean this way themselves. What I want to offer is that this T. rex "scale" - as suggested by the patterns discerned already - is best approximated by looking not at the exposed skin states of crocodilians with their regularly repeating, consistent, large, and architecturally sound scale designs. No the exposed skin state of tyrannosaurids is best approximated by comparison with the other archosaurs (i.e. birds) that have had to "reinvent" scales after losing them initially upon evolving a completely feathered countenance. When we look at both the small turberculate "scales" on the legs of birds and… wait for it... the minute "scaly" pattens discerned on some examples of carunculate skin of birds we can imagine a sort of novel tyrannosaurid integument that splits the difference between bird leg scales and carunculate skin. This novel skin morphology would be a lot more thicker and durable than carunculate skin but offer adequate blood flow for thermoregulatory and color flushes. Such a novel skin type combining elements of carunculate skin and bird leg tubercles would be consistent with the preposterously small tubercles of tyrannosaurids, their haphazard shapes, and offer immediate benefits for thermoregulatory and display functions.

Carunculate skin answers the question of why - when compared to other scaled dinosaurs - T. rex scales are diminuitive, non-architectural, no consistent shape, sort of globular, and devoid of rows, repeating patterns etc etc.

Oh yeah, and before you go "there goes Duane and his caruncles again" know that others have been pointing out this similarity between tyrannosaurid "scales" and carunculate skin as well…

credit Marco Muscioni
If you go back and review the T. rex skin impressions there are some very bumpy, textures reminiscent of carunculate skin. You will also notice the skin infoldings and the small size of the tubercles in carunculate skin is consistent with the unparalleled small size of T. rex "scales" and the skin creases shown in preservation.

Bell, 2017



You can take a wild guess how often the term caruncle comes up in the Bell paper (or the Carr paper for that matter). A big fat nada, zero, zilch, ninguno. I guess we don't have to talk about carunculate skin if we pretend it does not exist. Robert Bakker, I'm disappointed in you, especially since you have worked a lot with Luis Rey who gave us one of our first caruncle ridden theropods. Robert Bakker, you should read more antediluvian salad. Yes, the hate, disdain, disapproval, and ignorance for carunculate skin knows no bounds both from professionals and lay enthusiasts. And so perpetuates the false dichotomy of feather vs. scale, leaving out the retarded stepchild of carunculate skin… always the bridesmaid, never the bride.

Ye shall know it when ye sees it…

What was once scaled becomes feathered then becomes something new…

A quasi scaled, nekkid skinned, caruncled beast. Not completely serpent or fowl.

Ladies and gentlemen this is what modern theropods (i.e. birds) do when they get rid of their feathers. If we assume feathers and scales are more than a little competitive developmentally, when feathers diminish a nekkid skin is left. In order to toughen up this nekkid skin faux scales can be reinvented as they have been on the legs of modern birds. In other areas, especially of the head, nape, and neck a more motley growth pattern of various carunculate skin devices can commence. Carunculate skin can also have a superficially scaly facade. In large and gigantic theropods that mostly or completely lost feathers carunculate skin and tuberculate scales analogous to modern bird leg scales can potentially combine and envelope the torso as well, creating new motley and outlandish textures.

The dark little secret of carunculate skin is that it is found in not just one modern bird family, but many. We are left to consider two possibilities. Carunculate skin is basal to birds and quite possibly goes way back into theropods or: that it evolved independently in many different bird lineages. Both scenarios bode well for such epidermal growth to be quite common and expected in theropods that dispensed with feathers or possibly even some dinosaurs that never evolved feathers?!? (I'm looking at you Edmontosaurus)

Dang Tao Chicken "Do these caruncles make my feet look fat?"
And finally I leave you with a soft tissue preservation of another extinct giant theropod, a Moa. Do you detect some integumentary patterns that might in fact be construed as "scales"?



And finally, for the haters, social media harassers, stalkers, chastisers, discounters, "don't listen to Duane he is not teh true paleontologist", and all around perpetrators. You inspire me. Keep it coming. I stole the show with Spinosaurus and I'm doing it again right here. This C-walk is for you.
CARUNCLES BIATCH!! Up in Your Grill!!




Refs
  • Bell, P. R., Campione, N. E., Persons, W. S., Currie, P. J., Larson, P. L., Tanke, D. H., & Bakker, R. T. (2017). Tyrannosauroid integument reveals conflicting patterns of gigantism and feather evolution. Biology Letters, 13(6), 20170092.
  • Bell, P.R. A Review of Hadrosaur Skin Impressions. Hadrosaurs. Indiana University Press 2014
  • Carr, T. D., Varricchio, D. J., Sedlmayr, J. C., Roberts, E. M., & Moore, J. R. (2017). A new tyrannosaur with evidence for anagenesis and crocodile-like facial sensory system. Scientific Reports, 7.
  • Cau, Andrea. Those Scales Are Scales? Theropoda. June 7, 2017 webpage
  • Nima (Paleo-King) Are retro 90's Tyrannosaurs making a comeback? 2017 webpage
  • Witton, Mark. Revenge of the Scaly Tyrannosaurus. Mark-Witton.blogspot June 16, 2017. webpage


"A Long habit of not thinking a thing wrong, gives it a superficial appearance of being right, and raises at first a formidable outcry in defense of custom". Thomas Paine


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29 comments:

Nick Fonseca said...

Oh, there is mention of feature scales in Tarbosaurus. Though once again super tiny 6mm maybe. Check the supplemental material.

MrCrow said...

"maybe a bit of a fat layer too, and you have a pretty good heat retaining system" mammalian brown adipose tissue is good for warming up, but white adipose tissue, which is possessed by both mammals and sauropsids, isn't. Sauropsids don't have brown adipose tissue. So, would an extra layer of fat really help?

William Bailey said...

This could have been your most mature blog entry if not for some superfluous "social media" style rants in the middle and end. But you already know I have always been more critical of your style and how you present your arguments almost as a crusade than the actual ideas you're bringing in the table. Those are always interesting and sometimes do hit the mark. I do think that those "scales" in Tyrannosaurus rex are incredibly weird and a carunculate covering to make up for feather loss is a plausible one in my book. And I also agree that the way we picture dinosaur soft tissues and integuments will only complexify over the years. So yeah, my stance remains the same: I don't approve your style and rants but appreciate the discussion and possibilities you bring to the table.

Duane Nash said...

@Nick Fonseca Thanks for heads up. I edited for mention of some of the other specimens. The supp info is hard to get to and I can't find the bit about Tarbosaurus feature scales, just patches of basement scales. Are you referring to Albertosaurus? Regardless same difference as Albertosaurus has feature scales but are towards the bottom of the body. It is interesting that the more orderly patterns of tubercles all seem to arise from the abdomen thoracic area…

@MrCrow Havn't really given it much thought. The least fat could do is round out the body and give the animal a more heat retentive structural base.

@William Bailey Well you are beating a bit of a dead horse here now aren't you? But maybe you are under the impression I am seeking or sequestering your approval for some vaunted writing style you allude to? I write for primarily myself - this is a thoroughly selfish endeavor. I didn't see the type of blog out there that I would like to read so I made it myself. And perhaps if the shoe was on the other foot… if you had stalkers that - even after blocking them on one format they seek you out on others - maybe that would piss you off? Or people, that deliberately misquote or paraphrase you just to throw some shade? I have a right to how I feel and a right to express how I feel with or without yours or anyone's approval, especially on mine own blog. Yeah, it probably is better and more mature to not engage with them. And I do hold back a lot cuz there is some things out there said about me and mine ideas that I just have to walk away from.

What you are missing - what many gaff over quite a bit - is that I have never hidden the fact that I'm a person. That I have foibles, biases, shortcomings. In the sciences there is this thoroughly disheartening tone of researchers being non-emotional, that conflicts never breach over into the personal realm, that they are robotic analyzers. I beg to differ. And I guarantee that if you could hear what some researchers say behind closed doors and to confidantes… that what they say in privacy pales in comparison to my "social media" gaffes, which are more cute than ranty. I mean come on, I posted a video of the Crip-walk?!? I post professional wrestlers shit-talking?!?

MrCrow said...

Hello Mr. Nash. If the supplementary information is hard to get to
Here you go http://rsbl.royalsocietypublishing.org/content/roybiolett/suppl/2017/06/05/rsbl.2017.0092.DC1/rsbl20170092supp1.docx

MrCrow said...

Also keep in mind that bird reticulae aren't always completely uniform either.

William Bailey said...

Mr. Nash, I think there is a nice middle between ranters and "robotic analyzers" and I indeed see a lot of internalized indignation in your reply. However I will always respect and even admire the fact that you are writing for yourself. That is something I apply to my own writing forays. And I also understand how people misquote you can be utterly unnerving. I frankly didn't know you suffered such harassment and hate (I am still naive in some parts). Still, I do think your idiosyncracies may sometimes hinder the scientific message you are trying to convey. But as Jean Cocteau said "what the public pick you on about, cultivate it, it is you". So all the more power to you and let's indeed leave that horse carcass alone. It might not even be able to fossilize at this point. To go back on the matter, what do you think could have triggered dramatic feather loss in Tyrannosaurids ? Only the bulk modification or something else ?

Duane Nash said...

@MrCrow thanks, I glanced at it once when the paper came out. Forgot about it, now regrets. But i am not alone in these regards, seems like a lot of the blog postings/discussions on this topic are due for a more thorough review of the supplementary information. That being said, it is such a small supp they should have just put it in the main body of the paper. Regarding bird reticulae being less than uniform. Good point. I did iterate that my current thinking that a lot of these small, irregular tubercles might show a compromise between reticulae ( I think I just call them bird leg scales in the post) and carunclate like skin. I did leave that picture of that chicken to make (an unstated) point in that it blends carunculate growth with reticulae.

@William Bailey Looks up "internalized indignation". Yep, that's me. Look I can give examples of why I feel this way - I do have reasons for some of my outbursts and flame wars. And I do agree that some of the more casual, skim readers of my blog turn away from my ideas when I go on outbursts, rants etc etc. Personally, I don't want to lose a certain edge. When I feel slighted or looked over it just keeps inspiring more ideas. However I recognize that a lot of my critics - I have cultivated a few by now - would like to see me go completely over the rails because it could then allow them to dismiss me entirely.

So it is a fine line and I appreciate your concern that I could be losing interest due to rants/etc etc. At the same time I certainly feel like the Rodney Dangerfield of pale "I get not respect". At the end of the day I have to concentrate on the process, not the outcome. I currently have a backlog of ideas/hypotheses I need to get out in one way or the other. I know it hurts me because I am not among the peer reviewed professionals - the whole peer review process/publication process is due for a re-haul imo - I do have some very detailed and I believe useful ideas on that whole thing that I will document eventually. That being said I just feel the need to document and express my ideas because they - and I'm not bragging its just the truth - come to me faster than I can get 'em documented even in blog form, much less the drudgery, expensive, and painful experience of peer reviewed journals. If I did a fairly lengthy blog piece once a month I could keep going for at least two years with the stuff I have not even put down.


With regards to feather loss in tyrannosaurids it really is quite simple as they got bigger and they needed to shed heat. Even today you can look at the incipient trends of this in many large tropical birds/ratites etc etc. I think a mainly naked hided tyrannosaur is just the logical outcome of these trends.

Cheers, and I'm grateful for having an intelligent reader like you

Bk Jeong said...

If theropods went full caruncle all over the body and dispensed with feathers AND scales,

And do keep in mind that feathers can grow in the same part of the body as scales (cough Juravenator cough) and that it is also possible for scales to be shed and replaced with feathers (and back) in the same individual animal (ptarmigans)

khalil beiting said...

Completely agree Duane. Very insightful and it's great to receive so many implications from these scale impressions. I'm starting to love Tyrannosaurids all over again. So fascinating in regards to biology and ecology, with much to tell about the evolution of derived traits, especially in Dinosauria.

This is how I depict Tyrannosaurids on average, especially with the new data:
http://yutyrannus.deviantart.com/art/Sue-685284821
Of course I add far more caruncles and thick skin. Maybe a bushier tail for fun that could be used for communication and to break it's bodily outline.

And here's a pic to really make you think how small these scales are:
http://www.deviantart.com/art/Scales-687782838

By the way, seeing as how it's so beefy that it would emit too much heat to retain a coat of feathers, what are some other barrel chested/overly beefy Theropods that could also fit the bill of loosing a lot of feathers?

Nick Fonseca said...

@Duane Nash sorry about that. Yes you are correct, it is the Albertosaurus sarcophagus figure. I also found the website a bit hard to navigate. I have seen much better UI elsewhere. In any case I am sure you have it by now.

Don't worry about the haters man, haters got to hate. Please don't disappear on us. I couldn't take it after Jaime Headden rolled out. My blog roll has really shrank over the past few years.

Duane Nash said...

@Khalil Thanks. Oh how a complete mummified tyrannosaurs would be great like Leonardo or that recent nodosaur pulled from Canada. Complete head and everything. On beefy theropods, well tyrants seem to be more barrel chested than everyone else. Spinosaurus also had a good barrel chested torso too. There are of course other intervening factors and the sticky issue of when filaments first evolved on theropods so…. have fun with things in the meantime.

@Nick Fonseca Hey man thanks for letting me know I'm wanted. I guess I get kinda discouraged from some people who say stuff like "oh there goes Duane at it again, what kinda weird/unsupported/overly speculative stuff did he claim today?" said of course in a snotty, condescending tone. Yeah I wish Jaime was still around too. He doesn't get nearly enough credit for the soft tissue revolution with all the heavy lifting he did back in the day. I remember he got a lot of shit form people (i.e. 12 year old boys) suggesting cheeckless ornithischians. Some people in the online paleo-community can be insufferable. And boy could Jaime go off on some anatomical term laden verbose writings - he made me look up more than a few words LOL. He is definitely a loss, hope he is doing OK. But don't worry about me, I'm not checking out anytime soon. Too many people to irritate and I need more haters!! Great sculpting btw!!

MrCrow said...

Also, the environments of Yutyrannus, Albertosaurus, Gorgosaurus, and Tyrannosaurus weren't that different in temperature (in the supplemental data). So I still doubt they lost all the feathers. Certainly they lost some feathers as shown by the newly published impressions, but I still doubt they lost all of them. I still usually imagine them with some fuzz. The 2 Albertasaurines are about the same size as Yutyrannus too. (But of course they have scaly tails at least).

MrCrow said...

And scaly undersides too.

MrCrow said...

Well, either birdlike reticulate scales or bald elephantlike skin or in between like you suggest...wait, how does that work? In between carnuncles and reticulae? Just hard, bumpy skin?

Duane Nash said...

@MrCrow Regarding environment. Yes that has been a hang up for me and many others. Just keep in mind that derived tyrannosaurids may have had some additional thermoregulatory attributes apart from Yutyrannus. Countercurrent heat exchange - analogous to how the exposed bits of bird feet (including Emperor penguins & other frigid water birds) survive in such climates that one would assume turn to ice and frost bite.

"And scaly underside too" So far it looks like the inferior bits might be a bit more like "factory made" scales.

"bald elephant like skin… just hard, bumpy skin" Well probably no - at least not like nekkid avian skin which is wafer thin. The reason I suggested in between caruncles and reticulae is that it is quite possible there were skin adaptations and characteristics in tyrannosaurids - completely unique and outside of what we see in modern birds. The reason I would suggest this is that tyrannosaurids are ecologically and morphologically completely unique and outside of what we see in modern birds. It is a shame we don't have elephant birds, Moas, and especially phorusrhacids around because I suspect the exposed skin bits in these birds would offer much utility in comparison to the exposed skin bits of tyrannosaurids. Then again it is probably good to take an extra hard look at that preserved Moa bit.

Anonymous said...

So many questions... for starters, I'm confused about the concept of T. rex and Yutyrannus living in similar climates; there's lots of art out there that portray the latter in snowy landscapes whereas T. rex is shown in a sort of southern US bayou environment. Did I miss something? Did they find that Yutyrannus' environment was warmer, or that T. rex's was colder, or is the art simply misrepresenting? (In case it's not evident, I'm a total amateur and don´t read many papers on this sort of stuff, even though I eagerly follow news articles).

Also, wasn´t there some controversy about the correct classification of Yutyrannus and Dilong to begin with? I distinctly remember reading something about one of them being called a possible tetanuran (not to his face obviously), although I never heard anything about that afterwards.

Duane Nash said...

Hi anon (please leave a name btw next time) on environment. yes T. rex is often portrayed in a Florida looking environment. However it (and its relatives like Albertosaurus) got into some pretty northern climes that would have at least been cool. We are talking like Seattle or Portland type cold during the winter. So there is some overlap with Yixian and it is discussed in the paper too.

I never heard about the Dilong controversy although I do recall some murmurings about Yutyrannus being a tetanuran of some type but nothing seems to have come of it.

Kevin Franck said...

I have to admit, when it comes to Dinosaurs, while many definitely look repitilian, I've always pictured some as having a type of hide like that of Elephants or Rhinos

Alex said...

There's a name.

I wish I could remember about Dilong... all I recall is that there were many kinds of coelurosaur (Ornitholestes-types, and compsognathid-types) that looked very, very similar to the early tyrannosauroids, many traits in common, etc, making it difficult to actually separate them from one another. So it was difficult knowing if they had an actual member of the tyrannosaur linneage or simply something that looked like it. There was even talk of Monolophosaurus being the fully grown form of Guanlong or a larger species of the same genus, despite the fact that Monolophosaurus has not been traditionally considered a tyrannosauroid.

Re: colder environments, that is very interesting. I now wonder about Nanuqsaurus, probably the only tyrannosaurid to be represented as fluffy almost invariably since its discovery. Maybe some plucking is in order? Also, how do we know it wasn´t an early species of Tyrannosaurus? Wasn´t there recent suggestion that Tyrannosaurus arrived to North America from Asia, at about the same time as Nanuqsaurus lived?

Kevin Franck said...

I've found the ultimate in Dwayne Nash Swimming Pool design

Jurassic Waterhole

Duane Nash said...

Hey what's up Kevin, hope you are good. On elephant hides - yeah a lot of people do. From a distance many dinosaur hides would not look too different given the small size of the scales in many dinosaurs. As discussed here the puny size of rex scales would have given it a hide that basically looked scale - less.

@Alex Guanlong and Monolophosaurs nope, they are separated in time a bit. I've heard that about Nanuqasaurus. Sorry if I sound a bit rude but all these questions about taxonomy are a little off topic and you could just wikipedia them. I hope you don't take offense but taxonomy is not really my thing; I don't have unlimited time; and there are much better sources of info on these question than myself quite honestly.

Best

Alex said...

Haha I wasn´t expecting you to answer those. More like sharing my thoughts as ignited by your post. I tend to do that even IRL- people think I'm asking THEM, in reality I'm just thinking out loud.

Oh, and no offense taken; if there's something I've come to expect from the online paleo community, is rudeness. All things considered you're actually being quite polite. ;)

Duane Nash said...

@Alex No probs, I just am trying to damp down people asking me stuff that can be googled!! Most of the time I have to go look up those things anyone because I can't keep all of it in my head.

Anonymous said...

Yes the notable thing about those scales is their small size and irregularity.
They are even smaller than Mosasaur scale which are tiny compared to the size of the animal bearing them.
I think you are right that they are an evolutionary novelty that evolved to protect the skin when the ancestral feathers were lost.

Birds can tolerate having their scaly feet get quite cold but in really cold climates they often have feathers on their feet so perhaps Alaskan tyrannosaurs grew feathers or down in autumn and shed it again in the spring to avoid getting frostbite, especially on areas such as the tailtip.

LeeB.

Alessio said...

Man, it's quite weird that i read this post just as i returned home from a country fair where there was an exhibit of chickens, fowls and roosters... And many of them had those bigass, caruncled crests, whose texture immediately reminded me of Wyrex "scales"!

Heck, there was even a white-grey rooster who had a crest with two, long fleshy horns, sort of like the antlers you put on your theropod heads!

Duane Nash said...

I know they are great aren't they? The long fleshy horns are called split combs. I picked up a photo book called extraordinary chickens for inspiration and ideas. It was on sale for 9.98$. Score.

Alex Ruger said...

Hey Duane,

I think your general point, that carunculate skin plays a bigger role than generally thought, will stand the test of time. However, pursuing an alternate line of thought, one related to your SIGIL hypothesis: would a large number of smaller scales perhaps assist in thermoregulation better than larger ones? Just a thought.

Finally, the Wyrex scales look more like those of emu foot than anything else, as far as I can tell. They even have that same mid-line-in-rib pattern that the Bell paper mentions. If Dilong and Yutyrannus are borne out as tyrannosauroids (which at least seems somewhat likely) then perhaps tyrannosaurids were "scutellated" rather than scaled. Let me know what you think!

Emu foot pic link: https://incidentalnaturalist.files.wordpress.com/2015/07/dsc_0238.jpg

Thanks,
Al

Duane Nash said...

@Alex Hey thanks for comments and excellent points. On "scutellated" tyrannosaurids: in the paper they claim to have discounted these being scutes as the don't have a polarity. However this doesn't mean that the "scales" can not be reticula. I know a lot of minor but important distinctions. Reticula being the smallest of the scales discerned on a bird leg and what I presume you are referring to in the emu picture. So yes, you are probably right and a lot of people (including the authors of the paper) have been hypothesizing this.

Oh SIGIL, I didn't not even mention that with regards to this topic… although if one were to go out and look at ALL the skin impressions one might find some scale patterns suggesting of SIGIL: http://reptilis.net/wordpress/wp-content/uploads/2017/06/Tyrannosaur_skin_impressions-lite.jpg wink, wink I did not discuss for a reason… keeping for later.

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