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Tomozaurus — Tyrannosaurus variants 2015
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#integument #palaeontography #rex #theropoda #tyrannosaurus #tyrannosauridae #tyrannosauroidea
Published: 2015-02-18 05:42:48 +0000 UTC; Views: 13278; Favourites: 198; Downloads: 54
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Description
In recent months an internet friend of mine, SimKoning , has shown to be as familiar with the developmental biology of integument as I am, and someone with whom I can adequately discuss the evolution of integument in archosaurs. A topic of which I am extremely interested.Today he proposed the possibility that within our parameters, it is possible that feathered and unfeathered variants of the same species (perhaps more plausibly of the same genus) existed at the same time, even on the same continent, in different environments. The range of Tyrannosaurus for example, seems to stretch all the way from the hot, dry, Alamosaurus-flattened uplands of southern Laramidia all the way to the far north which was confined to total darkness for large portions of the year.
In regards to this, Sim challenged: "Thinking about this, what I would love to see is a speculative depiction of northern and southern T. rex subspecies, with the former being "wooly" and the latter being scaly.
The scaly sauropod hunter from the south and the grizzly northerner."
I decided to oblige. Call it repayment to Sim for giving me someone to discuss the evo-devo of archosaur integument with.
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Comments: 92
I can easily see how there could be variants within the same species. Maybe they just had different alleles.
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Very interesting idea. Truly a brain picker. At least this will chill out those who dislike feathered Rexes lol I might make a piece myself.
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Exactly what i think what was going on for some dinosaurs, at least in the skin department... Great to see i'm not the only one who envisioned different types of rexes, given the vastness of their range (also BrandonSpilcher had a similar idea)!
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Feathers insulate, working both to cool and to heat, making this sort of this a biological improbability of the highest order.
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What's a biological improbability is that a species that large having feathers at all, yutannosaurus had feathers because of a cool environment in asia. Tyrannosaurus lived a hotter climate and was absolutely massive, generating intense internal temperature. Yutannosaurus had feathers, t-rex did not, just because something is related does not mean they have identical features. No feather impressions have been found on t-rex, further cementing it's featherless nature even though feathers are found rather commonly in small theropods like microraptors and short dromeaosaurs like velociraptor, giving them an actual use like gliding or balancing on prey. Feathers are very complex structures that require lots of energy to regrow if lost in large amounts, something to ponder when t-rex constantly fights other large dinosaurs that could take huge masses off a hide. Besides a thermoregulative adaptation, feathers are a fanciful rarity on large theropods.
... if I sounded angry or rude, forgive me. I've been QUITE peeved at the excessive amounts of fluff people add to all dinosauria genera. To me, it's all an excuse to "cute up" all dinosaurs, even the sauropods! Sometimes I feel as if they try ignore the existence of reptiles because they are "abhorrent". A spinosaurus or carnotaurus with feathers and a bird like gait isn't natural, it's just plain visually appealing.
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Your absolutely right! Prior I was one to believe tyrannosaurs had feathers.. But after some research, you've brung up a lot of good points! I believe baby tyrannosaurs had downy fluff but lost them shortly... Maybe after a few weeks or at the most 2 years they shed them... I believe most large theropods had little if any feathers! Typically small predators had them, or some baby large theropods,
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thankgod some people know there shit
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Actually, I have since changed my opinion, and I believe Tyrannosaurs had feathes as adults, as it makes no sense for them to lose them.
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Thank you! a new back up would be elephants and ostriches. Their both the the biggest of elephantinea and the ratites respectively. Both also sport a distinctive lack of filament. Why? because the are both HUGE and dinosaurs were even BIGGER.
Anyways...
Why is Godzilla(2014) called fat? Have people forgotten about original Goji's thunder thighs?
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Ostriches actually do have feathers, which I thought was fairly obvious. And elephants are not scaly, they just have sparse hair and you can see hair on their tails. Also ground sloths had very dense fur, fur impressions from the freaking deserts in Nevada even shows they don't lose hair because of hot environments and large size.
Also as for your statement that T. rex didn't likely have feathers because we don't have impressions of that maybe you can say that to Australapithicus because we don't have skin impressions from them showing hair. Really as said before there isn't much of a reason to lose feathers as they can keep in heat or lose it, hair can also do the same. Also Yutyrannus was found with feathers so that's enough evidence to say rex is feathered, it's not like prehistoric birds or mammals have scales because we don't have skin impressions showing feathers/fur on many of them. Really the skin impressions showing scales on Tyrannosaurids are places that can logically have scales on a feathered animal.
Also Tyrannosaurus might as well be a mesotherm which is a greater reason why feathers might not be lost, *hintslothshint*.
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People have gotten into this habit of saying "birds therefore dinosaurs"... It is ridiculous. Birds are heavily derived forms and only a tiny subset. They also fill very different ecological niches and lived in very different climates and environments. There's value in taking inspiration from birds, but many fall into the trap of over-correcting: making dinosaurs as resemble birds as much as the early scientists (circa ~Richard Owen) made them resemble lizards. That's not a very rigorous approach or position.
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Lol. Says the guy who added feathers on their Dire Wolf's neck.
Dinosaurs were certainly not giant lizards. Dinosaurs are highly varied creatures but they certainly weren't mutated lizards. Lizards are squamates while dinosaurs are archosaurs, a group that also includes crocodiles and *gasps* turtles. Sure early scientists made dinosaurs resemble lizards but that is an outdated view which formed since they barely even had any fossils and science *gasps* changes.
Also as I said above Tyrannosaurus rex had relatives with feathers and most if not all basal coelurosaurids, the group of dinosaurs including Tyrannosauroids, which we have skin imprints from show feathers. Basal Tyrannosauroids also show feathers on them. Also birds do fill many different niches and are found in different places in the world but there are ZERO birds that lack feathers. Just because Yutyrannus lives in a really cold region doesn't mean Tyrannosaurus should lack feathers for living in a hotter region, if that was true Amur Tigers would have fur (which they do) but say lions should have no fur at all because they live in warm regions.
Also yes birds are heavily derived forms of dinosaurs and are only a fraction of the true diversity of dinosaurs but that doesn't mean every other dinosaur was scaly. Fossil evidence proves many dinosaurs did have feathers. Furthermore your reason suggests that say Notharctus (an early primate) would be lacking fur but a Gorilla can have tons of hair.
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why you getting personal now.lol.
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So you have no points against me.
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hmm those werent feathers.but it could be an option of corse i have nothing on you your not worth knowing
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So you basically made fur alphas exactly identical to some of your feather alphas. Lmao.
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I did not intend to say that they lack intungment mentioned and I find that regrettable. Forgive the misinterpretation. Now, let me make myself clear. Your sloth is one of the SMALLEST of ground sloths, tiny compared to megatherium. Most sloths lived in forests or swamps, he's the odd man out. The shagginess can be explained by the fact that deserts become freezing cold at night and the ice age was called that for a reason. Australopithecus? Really? Terror birds are considered feathered because? They are birds with beaks and all, provided by evolution. Dinosaurs may have fathered birds but they were not birds. Feathers serve a purpose. Penguin feathers are used for swimming and hawk feathers for flying. Feathers on something GIANT would serve NO purpose. Cooling? Those arms are too inflexible and they would be torn off by other t.rexes. Also, they sorely lack barbules. Gigantothermy is the reason why elephants, paraceratheriums and sauropods have barely any intungment: they don't need it. Yuttano huali and woolly mammoths were shaggy because of cold climates. Rexes lived in swampy, humid forests where heatstroke is a thing and the least amount of feather or hair is optimal. Case in point: the feathers you are looking for are not here.
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Lol. Even if deserts can be cold at night they can still be hot at day, pumas aren't extremely shaggy in deserts so why should sloths be if they are so cold that thick fur is definitely needed. Even if Australopithicus was a weak example why don't we just claim early primates had scales instead of fur since we don't have much skin impressions of fur on them. Also we have fossils of Tyrannosauroids, and coelurosaurs in general, with feathers. Obviously not all dinosaurs had feathers but all coelurosaurs, including Tyrannosaurs definitely did based on phylogenetic bracketing, we don't need birds for this considering we have stuff called fossils. Also if hawk feathers were just used to fly than what use is it for them to be all over the body of hawks. Penguin feathers are used to cool down and keep in heat not solely for swimming. Emu feathers, the feathers most similar to those Tyrannosauroids had, are used to keep cool down and keep in heat as well. Also barbules are not attached to bone so there's no reason for Tyrannosaurus to lack barbules. Besides that feathers are not limited to an animal's arms so definitely there was space to have feathers, also T. rex's arms were not immobile. Besides that elephants and rhinos had semi-aquatic ancestors while who knows if dinosaurs actually had feathered ancestors so that makes your example using sauropods null. You even ignored the fact that all sauropod skin impressions show scales, which shows they actually had integument, while many coelurosaur skin impressions show feathers.
Why would Yutyrannus suddenly evolve feathers because of a cold climate? Juravenator didn't live in a freezing climate but it had feathers and gigantothermy isn't a good enough reason to loose feathers if they can cool down and/or keep and animal warm. Tyrannosaurus rex did live in a place that included swampy areas and was humid but Hell Creek wasn't tropical considering that a good modern analogue (temperature wise), northern Florida, actually snows sometimes. Even in hot days feathers can cool an animal down.
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There are so many gaps in the logic you just presented, lol
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Yeah, and it's not like the hesei Godzilla watched his weight either, yet I love the original, hesei and 2014... He's a giant Permian sea reptile he's not gonna look so skinny, if you want a skinny Godzilla watch Zilla
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Nice idea! It's entirely possible as well! It'd actually be pretty funny if a scaly T. rex was walking around and met a feathered one! XD
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Wow! Nice idea that you came up with!
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As explained in the artist's comments, SimKoning came up with the idea. I just illustrated it and endorse it as a possibility.
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Considering Hell Creek wasn't all that immensely warm to begin with, seasonal variance of integument makes a lot of sense; though I doubt total feather moulting would be a part of that, myself.
I'd actually thought of a similar concept with dromaeosaurs in the past, and the layout would be similar. What I came up with was this;
- Spring coats were a middle ground between the winter and summer coats, with enough feathers to keep the animal from getting hypothermia from high concentrations of rain. Naked skin is a basic pink.
- Summer coats covered the heaviest on the areas that faced the sun most often and were less dense on areas that rarely, if ever, saw sun exposure. The naked skin becomes a quite light shade of pink to reduce heat absorption.
- Fall coats rapidly thickened and expanded as the temperatures dropped, with the exception of the legs. Naked skin darkens from a light pink to a dark pink.
- Winter coats were the thickest by far, covering almost the entire animal aside from the head in feathers to protect against cold conditions. Naked skin is a very dark pink, almost black, to absorb more heat.
Similar ideas may be able to work with tyrannosaurs, with some modifications. Regional differences would then simply be differences in pattern (ex: a Tyrannosaurus from Texas only has spring and summer coats, while one from Alberta has all four coats), not fully unique coats for different tyrannosaur "types". I'd expect more behavioural difference in regions than physical ones, honestly; but that's just me.
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I confess I am not partial to a fully "naked" coelurosaur, even if it is as big as Tyrannosaurus rex. The body ratio of dinosaurs, because of their volumetric distribution, is different from those of mammals of the same size. Hence, the body ratio of Tyrannosaurus is equal to mammals that are quite smaller than elephants, like bears. So, to me, even in dry and warm climates, T. rex would still be feathered. Also, feathers are better at thermoregulation than hair and help the animal cool down when the temperature is high.
Still, you bring a very interesting aspect of Tyrannosaurus's relationship with its environnment. It is totally possible there was variation between populations depending on wich part of the continent they lived. The species is so wide-spread, it's not unreasonable to think they would look different from one place to another.
But maybe Tyrannosaurus rex developed a very generic look that could fit in most environnments. I don't know, I'm asking myself those questions too. ^^
Anyway, very good art as usual and I particularly love the wrinkles and loose skin you give to your dinosaurs. They look all the more real.
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The point I frequently stress is that we aren’t limited to making rough guesses based on surface area/volume. We have several large dinosaur taxa, such as hardosaurs and Carnotaurus, which were covered entirely, or nearly entirely, with scales. If we assume that protofeathers were ancestral to Dinosauria, if not Ornithodria, it follows that these giant scaly taxa had “fuzzy” ancestors. This begs the question as to *why* feathers were independently reduced or lost in favor of scales in these lineages. Note that this may have occurred five times in different lineages, all of which produced rhino+ sized taxa. One could argue that air sacs and large tails increased surface area, but air sacs and gular fluttering cool via evaporative water loss, which is physiologically costly. Thus adaptations that increase surface area and heat transfer without water loss would likely be primary with evaporative cooling being a sort of “backup” when the primary solutions fails. Regarding elephant vs. Tyrannnosaur surface area, are the trunk, very large ears, and four long legs being taken into account? Are the thermoregulatory advantages and water-conserving properties of scuta and scutella over feathers and apteric skin being considered? Do our assumptions regarding surface area and thermoregulation fit with what’s observed in the fossil record?
If this hypothesis is correct, then it follows that giant tyrannosaurs in hot climates would have been under similar selective pressures as other giant dinosaurs; therefore, feather reduction, at least in adult animals, seems plausible. Otherwise, one may have to resort to extraneous assumptions to explain why tyrannosaurs were “special” relative to other giant dinosaur taxa of which we have excellent scale impressions for. Of course, there is the issue of Yutyrannus, but it should be remembered that the Yixian ecosystem was devoid of crocodilians and appears to have had a temperate climate. Hell Creek on the other had palm trees and crocodilians, suggesting a warm temperate climate at the coldest, and possibly subtropical. However, Scotty (from Saskatchewan) has been reported as coming from a deciduous forest ecosystem, which suggests relatively cool winters, which is partly what got me thinking about this possibility.
I think the best approach is to find explanations that best explain the patterns we observe in the fossil record. That way, we can form a hypothesis or explanatory model that may be more predictive when inferring the integument on taxa in which data is otherwise lacking. Moreover, this model could be tested via future discoveries.
Lastly, at the very least, this idea was meant to illustrate a false dichotomy, an error in logic that assumes only two possibilities when there may in fact me more.
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Point taken and you articulated your take on the subject quite well.
Carnotaurus' skin impressions have yet to be officialy described but
the need to destroy fals dichotomies is welcome and engaging. ^^
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People have gotten into this habit of saying "birds therefore dinosaurs"... It is ridiculous. Birds are heavily derived forms and only a tiny subset. They also fill very different ecological niches and lived in very different climates and environments. There's value in taking inspiration from birds, but many fall into the trap of over-correcting: making dinosaurs as resemble birds as much as the early scientists (circa ~Richard Owen) made them resemble lizards. That's not a very rigorous approach or position.
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Not keen on total filament loss, but in any case, gradients in tegument are commonplace nowadays. Great show!
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Maybe not scaly, but certain glabrous
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This is great. Not only this but you could have long and short coats depending on seasons.
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Birds in temperate regions have less insulation during the summer, so yes, it's probably more likely than not.
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Yes, that is definitely a possibility.
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This was quick.
I also really liked discussion with him,
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I adore this idea, and the Polar Tyrannosaur in my scraps can attest to that, but what sort of evolutionary impetus is there for the loss of feathers? I know it could happen, but why would it?
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This my the Facebook post that was part of this discussion
The short answer is great body mass combined with a hot climate. The long answer is given below
"Here is what I think is going on with dinosaur skin. This is a hypothesis, not a statement of fact, obviously.
Reticula are simple epidermal tuberculate scales that start out with an outer layer of beta keratin which is lost during development. These represent a inhibition grade below that of apteria (naked skin). The beta keratin is lost, resulting in a soft, pliable surface on the plantar surface of birds and likely non-avian taxa. Scuta and scutella are large to intermediate respectively and are in a less inhibited state. The scuta of many animals extend into the dermis and are vascular. The beta keratin armor along with vascular tissue would allow for heat exchange without evaporative water loss. The next grade from scuta/scutella may have been a scute equipped with a bristle or quill and attached to dermal muscles; this, along with a display function, may have increased surface area controllably and further assisted in thermoregulation. In smaller, derived, endothermic ornithodiran ancestors, the bristles may have replaced the scuta entirely on large regions of the body.
Thus, with history given above considered, it is possible that what we see today with avian scales (and by plausible extension non-avian dinosaurs) is a classic case of ontogeny recapitulating phylogeny. The default state of bird integument is now feathers, but inhibition of feather development results in various grades of primitive morphology. Therefore, in a sense, dinosaur scales are scales, but they form through something akin to atavism or paedomorphisis.
The "reticula" on the bodies of many non-avian dinosaurs may have been intermediate between avian reticula and scutella, i.e. small tuberculate scales that retained the beta keratin layer. Visually the may have resembled avian reticula expect with an beta keratin outer layer and a alpha keratin inner layer like tuberculate lizard scales. This makes more sense from a functional standpoint as the absence of beta keratin would seem a needless disadvantage.
In Gorgosaurus, we see patches of "sparse scales". I suspect that what we are seeing is a developmental transitional state from feathered to scaled, or at least an intermediate state in an adult. Dr Holtz once posited that a juvenile could be born fully feathered, and as it grew, rather than new feather follicles growing in, scales may have grown, gradually increasing the ratio of scales to feathers. In the birds I've looked at, the denser the feathers, the fewer the scales. I'm not aware of densely feathered feet with a full compliment of scales underneath; so scaly dinosaur skins may have been sparsely feathered at most.
Applying this speculation to hadrosaurs, it's conceivable that juveniles may have been feathered like Tianyulong, or Kulindadromeus, but transitioned to a mostly or entirely scaly adult form (except, perhaps, in temperate regions where the adults may also have been fuzzy). The problem with the scenario is that sauropod juveniles appear to have been entirely scaly. I suspect this may have been due to the fact that sauropods may have been poikilothermic to a degree, which is something supported by recent research on dinosaur metabolism. Psittacosaurus had a metabolism below that of most birds and mammals and mass burial of juveniles may indicate hibernation. Considering Yixian lacked crocodile taxa, this might explain the lack of insulation in a temperate region. A juvenile, highly cursorial tyrannosaur, on the other hand, would have benefited greatly from insulation, since without it, a large amount of calories would be lost maintaining a high body temperature.
On very large dinosaurs, the problem would not have been the need to *reduce* heat transfer (thermoinsulation), it would be the need to increase it. This could be achieved by increasing surface area (quills, plates, frills, sails etc.) or by transferring heat through vascular scutes (like crocodiles). Thus scutes/osteoderms and long quills running from scutes may have had a thermoregulatory function while also doubling as armor. Elephants achieve a analogous function with their large, vascular ears and sparse hair. Feathers act as insulators as I've said, however avian feet can increase heat transfer by increasing blood flow, and storks and vultures even defecate on their feet to cause evaporative heat loss. Moreover, the bill of some birds can shed heat. Scutes, horns, plates and quills projecting from the body all would have increase surface area and/or increased heat transfer rates in giant taxa. Decreased bloods flow in scutes would reduced heat loss/gain while the bulk of the animal would have provided the insulation otherwise provided by a feathery coat in small taxa.
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Very interesting and informative post. I hadn't ever considered the idea that scales could grow in between the feathered areas as the dinosaur itself grew. I found the idea of a feathered juvenile turning into a fully scaled adult impossible: at most I think, however, that the scales would have grown in place of the feathers during growth, and then perhaps those feathers could have been lost. I hope we find some good impressions to solve this. I wish that the Gorgosaurus impressions were published, then we'd be able to know if they were more likely feather follicles or true scales...
As for the scutes: Has anyone examined the scutes of Ceratosaurus in detail? I'd be interested in knowing if they could have served a thermoregulatory function.
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Ceratosaurus doesn't have scutes, it has osteoderms, these are not the same thing.
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I know, I'm sorry. Scutes are repressed flight feathers, osteoderms are bony structures. I misspoke, I apologize.
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