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February 4, 2012
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This is the long awaited post for my point of view on this question. I finally finished it inspired by the recent post of the deviantartist karkajou1993.

EDIT: Now there is an updated and corrected blog post of this entry! Check it out: ktboundary-smnt2000.blogspot.i…

EDIT 2: the blog version has been updated with some new infos after an interesting post by Matt Martyniuk (link: dinogoss.blogspot.it/2013/09/y…). Go to read it!

1 - The ancestor of Dinosauria is feathered. Now we have proof that feathers were present both in theropods (Sinosauropteryx, Epidexipteryx, Velociraptor, Beipiaosaurus, Dilong, Anchiornis, etc..) other than ornithischians (Tianyulong, Psittacosaurus). Even if we cant 'rule out that the two groups of animals have developed these structures independently, it is extremely likely that the common ancestor of both possessed 'em. As it is unlikely that ungulates and felines have developed fur each independently from a hairless common ancestor, at the same time we can say that if Rahonavis and Heterodontosaurus were feathered is because even their "ancestor" was. Further evidence in support of this are pterosaurs's pycnofibres. Pycnofibre is nothing else but a bizarre word for structures most likely homologous to the proto-feathers of the dinosaurs. As the ancestor of Dinosauria is the same one of Pterosauria and since both orders are feathered, this archaic animal and all his descendants MUST be feathered.
2 - The polar dinosaurs MUST be feathered dinosaurs, then the categories of animals to which belong MUST be also feathered. Numerous data tell us that all dinosaurs were warm blooded, from gigantic sauropods to tiny Scansoriopterygids. Since every endothermic tetrapod (excluding cetaceans) is covered by thermoregulatory structures in temperate or cold climates, this reasoning can be applied to dinosaurs as well. Then the members of Neovenatoridae, Troodontidae, Dromaeosauridae, Tyrannosauridae (aka Deinodontidae), Ceratopsidae, ornithischian dinosaurs considered as Hypsilophodontidae, Rhabdodontidae, Spinosauridae, etc. are feathered, at least in temperate climates. This leads us to conclude that the ancestor of each group must also be feathered, and also its ancestor and so on. This brings us back to point 1.
3 - At different temperatures, different thickness (but NEVER TOTAL EXCLUSION) of plumage. Derivation of point 2. We said that Hadrosauridae and Ceratopsidae have feathers. But we have the fossil fragments of skin belongin' to both groups (Edmontosaurus, Triceratops) that indicate the presence of scales. So is step 2 wrong? Not necessarily. Just think of today's elephants that live in hot climates (and they still have some hair) and their relatives, the mammoths provided by a thick woolly coat. Or you can even mention rhinoceros and woolly rhinos, warthogs and boars, etc.. From this we can infer that dinosaurs possessed coverings more or less dense depending on climate and latitude. Moreover, the presence of scales does not exclude definitively the presence of proto-feathers small and sparse like the hairs of the current pachyderms. Further confirmation of this point is the skin of the afore-mentioned Triceratops: it's scaly but it presents quill knobs similar to those of his distant relative Psittacosaurus.
4 - Different weights, Different plumages. Derivation of points 2 and 3. Another factor to consider is the weight. In today's warm-blooded animals, in  the EQUATORIAL AREA, species generally weighing more than a ton or a ton and a half have a sparse covering of feathers / fur. Similarly, the dinosaurs of EQUATORIAL CLIMATES that weigh over that threshold should not be heavily coated by integumentary structures. Proof: the small dog-sized Tianyulong has a thick plumage, while Corythosaurus, heavy as a rhino, is "hairless".
5 - If you are a carnivore like T. Rex, you are feathered. Derivation of point 4. So far we have only mentioned large herbivores  big as elephants, but what about theropods of comparable size? Are they also to be considered scaly? Here comes the issue of metabolism. Citing Tyrannosaurus just to make an example (but if you want, you can do the following comparison with any other giant carnivorous dinosaur), this saurischian, despite weights as an African elephant, consumes an amount of energy equal to that of a 1-ton bear. This is because, although there may be a several tons herbivore with a metabolism more or less comparable to those of elephants, a giant carnivore of the weight of T. Rex (or heavier) can exist only in marine environments. Since Tyrannosauridae (and other large theropods of similar tonnage) do not live in oceans, since it seems that no land predator covered in fur actually lose his fur around 1588-1749 kg (like the bear Arctotherium) and since a carnivorous dinosaur that weighs 6 tons generates an amount of heat similar to that of a 1-ton mammal predator, there is no reason that big theropods must loose plumage. EDIT (April 2012): we've got the final proof of giant feathered theropods! Yutyrannus hauli (Xu et. al., 2012) is a giant, maybe Baryonyx sized tyrannosauroid from the Lower Cretaceous of China and it shows the unequivocal proof that big tetanurans had protofeathers. It's not very surprising if you agreed with the many points of mine, but it sure is a pleasant surprise.
6 - Not the whole body is feathered in the same way. When it comes to feathered or furry animals, we generally thought to the tegumentary thickness of the Star Wars's Chewbacca. We must however remember that the length and distribution of these coatings vary not only from species to species, but also from different areas of the animal's body as well. The hairs of the muzzle of some bovids are very short, while in other parts like the chest or shoulders may be long and thick (like in the bison). To also cite birds, vultures have thin feathers on the neck against sunburn, while having a more dense plumage on the body. Among suids and some other related species, some have fur (wild boars, peccaries) while others can be considered almost hairless (pigs, babirusa). Such disparities are also present in many other animals: rodents, insectivores, primates, etc.. so, albeit the previous points are not incorrect (in fact, I think they are not), the feather / fur factor cannot be entirely understood and there may always be some exceptions. In the world of dinosaurs, an example of this exception are Ceratosaurus and Carnotaurus. But you must also remind that exceptions are not the rule.

This post has been written not to impress or manipulate the minds of others or, even worse, indoctrinate forcibly what I think about it, but it is a plain statement that justifies the presence of feathers on my reconstructions of dinosaurs. When I'll put drawings of feathered prosauropods and carcharodontosaurids or whatever in my gallery, you now know that I have an outlandish explanation of why I have portraited 'em in that manner. I'm not absolutely saying that I'm an expert, I'm a genius while you're jerks, I'm smarter or other nonsense stufflike that. I just need to be understood. Or, if you prefer, pitied.
So avoid stupid, negative and quarrelsome comments. I do not need 'em, but most important of all, I do not want them. You want to insult, mock or make me change my mind for having expressed my idea? No thanks. As I do not want to do that to you, I ask you not to do it to me. I know, it's selfish and stupid, but this is my request. Then, critics must abstain.

I'm done with this. Good day to you all.

PS: Sorry for the bad english

  • Listening to: Sherlock Soundtrack
  • Reading: My entry
  • Watching: My sister's dog
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:iconlordofstamps:
LordOfstamps Featured By Owner Aug 15, 2014
Actually pterosaur pycnofibers are structurally different from protofeathers.  The current available impressions of pterosaur integuments are not like the "quills" found on many of the dinosaur specimens in the fossil record.They probably aren't homologous.
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:iconsmnt2000:
Smnt2000 Featured By Owner Aug 15, 2014  Hobbyist Traditional Artist
You're right noticing that and probably I should re-write that sentence. 
However, from Witton's book on pterosaurs (pg.51) : "New dinosaur discoveries reveal that feather-like or hairlike integuments may be more common to the group (Ornithodira) than previously recognized, so perhaps the idea of a completely fuzzy Ornithodira should not be ruled out just yet".
The main point I wanted to make is that 'fuzziness' might be a common trait  to all ornithodirans - some groups developed feathers (theropods and ornithischians) while others pycnofibres (pterosaurs).
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:iconlordofstamps:
LordOfstamps Featured By Owner Aug 15, 2014
Though I personally think the possibility that Ornithischians developed these structures independently can't be ruled out. I mean the structures on Psittacosaurus and Tianyulong are rigid quills, not soft protofeathers. They were probably used in display or possibly even defense (a possible forerunner to the armor of stegosaurs and ankylosaurs?) 
As for Kulindadromeus, the structures on it are unique, especially the ribbon-like stuff on it's legs.  As one guy on   Archosaur Musings pointed out

If the filamentous integument is comprised of extensions from scales, wouldn’t that suggest that these structures might not be homologous with feathers?

Maybe fuzzy integument emerged three times among ornithodirans.



Oh and there isn't really any proof of therapod feathers outside of Coelurosauria (Scirumimus was later revealed to be a Coelurosaur and the "quill knobs" on Concavenator's arms might just be  tendon attachment points because they are irregular;y spaced. Quill knobs are spaced evenly.)

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:iconsmnt2000:
Smnt2000 Featured By Owner Aug 16, 2014  Hobbyist Traditional Artist
I don't understand why they say that Psittacosaurus quills are rigid. They really aren't.
By looking at this picture for example (oficina.cienciaviva.pt/~pw011/…, we can se that they aren't even stiff, but curved, and I think that the real life appearance wouldn't be so different from a antelope's mane rather than the porcupine's quills. Beipiaosaurus, a fully feathered coelurosaur, had some real quill-like structures called EBFFs (2.bp.blogspot.com/_OVH5UC-R50w… which are the most simple feathers found, maybe even more basal than ornithischian 'quills'.
I seriously doubt that they are the tyreophorans' osteoderms forerunners since the two species you've cited aren't close relatives of that group.

Feathers may actually originate from dinosaur 'scales'. From DinoGoss.blogspot (link: dinogoss.blogspot.pt/2013/09/y…: "Reticula, often referred to as "tuberculate scales", are the bumpy structures on the plantar side of the foot. These are also, famously, the type of "scales" found in just about all non-feathered stem-bird skin impressions. And here's the kicker--these have very little to do with the "scales" of squamates or even crocodiles.
In modern birds, the reticula, unlike feathers or scutes, do not form from placodes. Unlike lizard scales, scuta, and feathers, they're made not of beta-keratin, but alpha-keratin (the same as mammalian hair and amphibian 'warts'). The reticulae do start with an overlying beta-keratin layer that is shed during development. While they don't form from placodes, they appear to be similar to the pre-placode stage of feather formation. Reticula apparently never morph into scales in nature (I suppose ptarmigans start with naked skin on their feet?), this can be induced in the lab. Dhouailly suggests that, given the weight of the developmental evidence, reticula appear to be feathers which are arrested in a very early stage of development.
You read that right--tuberculate "scales" are probably modified feathers! So, those fossilized hadrosaurid mummies covered in "scales"? It's possible or even likely that they had feathered ancestors, and evolved in such a way to stop the development of feathers early on, instead yielding a fine, pebbly skin covering derived from old feather genes."

You can find the original study here: www.ncbi.nlm.nih.gov/pmc/artic…

Kulindadromeus has feathers of the morphotype 1, 2 and 3, just like theropods. The really unique structures are the ribbon-like feathers on its legs, which are still a unique kind of feathers.
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:iconlordofstamps:
LordOfstamps Featured By Owner Aug 16, 2014
It is worth pointing out that the ones in Beipaiosaurus, the quills were flattened. The ones in Psittacosaurus and Tianyulong were round.


Actually it had a type 1 like structure, a type 3 like structure and the ribbon-like structure on it's legs (according to Wikipedia). A type 2 structure wasn't mentioned.
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:iconsmnt2000:
Smnt2000 Featured By Owner Aug 16, 2014  Hobbyist Traditional Artist
"It is worth pointing out that the ones in Beipaiosaurus, the quills were flattened. The ones in Psittacosaurus and Tianyulong were round"
What do you mean with flattened and round, precisely?

"Actually it had a type 1 like structure, a type 3 like structure and the ribbon-like structure on it's legs (according to Wikipedia). A type 2 structure wasn't mentioned"
Ops, my bad. I was sure that there was another morphotype of feathers. I should re-read the paper.
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:iconlordofstamps:
LordOfstamps Featured By Owner Aug 16, 2014
Look at the Wikipedia article on Tianyulong. It mentions that.
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:iconsmnt2000:
Smnt2000 Featured By Owner Aug 17, 2014  Hobbyist Traditional Artist
I've read it but I still don't understand. I'll read the full paper if it's available somewhere.

Citing Wikipedia once again: " Both the filaments of Tianyulong and the filaments of Beipiaosaurus were long, singular, and unbranched. In Beipiaosaurus, however, the filaments were flattened. InTianyulong, the filaments were round in cross section, and therefore closer in structure to the earliest forms of feathers predicted by developmental models".

Interesting fact, this from the supplementary information: "After the accepting of this manuscript, a new type of feather, the elongated broad
filamentous feathers (EBFFs), is reported in the therizinosaur theropod Beipiaosaurus. Both the filamentous integumentary structures in Tianyulong and the EBFFs in Beipiaosaurus are relatively long, singular and unbranched; however, the former has a circular cross-section, while the later is planar. EBFFs are more closer to the predicted most basal feather morphotype (stage I) than the composite feather structures in other nonavian theropods. Therefore, the similarities between the filamentous integumentary structures in Tianyulong and the EBFFs in Beipiaosaurus favor a homologous explanation for the filamentous integumentary structures in Tianyulong and feathers"
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(1 Reply)
:iconhellraptor:
Hellraptor Featured By Owner Apr 15, 2014  Hobbyist Digital Artist
would you say all dinosaurs exept sauropods,stegosaurs and ankylosaurs could have been featherd ? I thinks it highly possible.  i think hadrosaurs could have had feathers aswell since soem lived in colder regions like Edmontosurus so a insulation would been obvious. And also since many dinosaurs migrated from cold to warm areas, a warm insulated body would have helped them on the journey.
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:iconsmnt2000:
Smnt2000 Featured By Owner Apr 15, 2014  Hobbyist Traditional Artist
I think that feathers were the ancestral condition for all the members of Avemetatarsalia. Some species lost feathers while other kept them.
I'll have to re-write this post in a more serious way, but the main points will be the same.
The main difference is that I'll talk about dino skin with all Martyniuk and Dhouailly's considerations.
You can read more about it here: dinogoss.blogspot.pt/2013/09/y…
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