GlaciusTS wrote:So it has been proven that T-Rex was an opportunist and behaved as both a scavenger, and a predator (when the prey was somewhat small and not too difficult to obtain). We have learned quite a few things in the past about dinosaurs, that's for sure. But what many people don't consider is when they changed. Now, I know a few basic things about dinosaurs, but I'm not entirely familiar with every aspect of their history.
Pangea wrote:Basically, the entire coelurosaur (Tyrannosaurs, Raptors, Oviraptorids, Compsognathids, Troodonts, Therizinosaurs, and Ornithomimosaurs) group had feathers. The only ones that had modern feathers were raptors, ovis, troos, and possibly ornis. The rest had protofeathers.
GlaciusTS wrote:Pangea wrote:Basically, the entire coelurosaur (Tyrannosaurs, Raptors, Oviraptorids, Compsognathids, Troodonts, Therizinosaurs, and Ornithomimosaurs) group had feathers. The only ones that had modern feathers were raptors, ovis, troos, and possibly ornis. The rest had protofeathers.
Is there any evidence as to when Coelurosaurs acquired feathers? A common ancestor perhaps? Is it possible that some members of a species shed their feathers for periods or lost them?
Atouk wrote:As for Tyrannosaurus Rex, what carnivore doesn't like a conveniently provided, pre-killed meal? IMHO it is ludicrous to say that he/she was either predator or scavenger; almost certainly he must have been both.
GlaciusTS wrote:Is there any evidence as to when Coelurosaurs acquired feathers? A common ancestor perhaps? Is it possible that some members of a species shed their feathers for periods or lost them? I find it pretty intriguing. I know birds of today all have feathers, I'm pretty sure there are no exceptions, but I know they moult, and some species have less noticable feathers. I'm unfamiliar to the anatomical specifics and purposes of protofeathers. I don't mean to pry with questions, you may not have answers for them all. I'm just thinking of the possibility that some Coelurosaur may have been exceptions to the rule, similar to how many current species have evolved with minor exceptions. Some members of a species can appear bald (maybe having whiskers or very short unnoticable fuzz) such as hairless coyote and members of the cat family while very close relatives or alternative breeds of an animal can be very furry. Or perhaps during early stages, a species who had previous began to grow feathers may have migrated and evntually lost the need for them? To shorten the question, Is there any evidence, either proving or disproving, that some members of Coelosaur may have either been bald or at least appeared bald?
On the Primal Carnage Forums, I wrote:We've known for quite a long time that Coelurosauria had feathers. Birds, Deinonychosaurs, Tyrannosauroidea, the like. But for a while, we had no evidence to prove that feathers - or even more basal feather-like structures - existed anywhere on the Dinosaur family tree outside of Coelurosauria.
Imagine our surprise when Otto the Sciurumimus came to light. This small Theropod was beautifully preserved with what is clearly a coat of fuzz. Thanks to the wealth of discoveries made in the Yixian Formation, a small Theropod Dinosaur found with a coat of 'protofeather' fuzz is nothing new at all. The funny thing, however, is that Sciurumimus is only relatively distantly related to the Coelurosaurs. Sciurumimus is actually a Megalosauroid, a member of the group which includes Megalosaurus and Spinosaurus. Using Phylogenetic Bracketing, we can now push back the origin of feather-like structures much farther into the history of the Theropods; We can now assume that the most recent common ancestor of the Coeulurosaurs and the Megalosauroids, and all of that ancestor's descendants (a group known technically as the Tetanurae) likely had at least some kind of feather-like structure somewhere on their bodies.
Now, Dilophosaurus is not a member of Tetanurae, so why would that be quilly as well, you may ask? Tianyulong and Psittacosaurus hold the answer. These two animals are Ornithischians, which are as distantly related to birds as a Dinosaur can be. In spite of this, both Psittacosaurus and Tianyulong, two Dinosaurs from different branches of the Ornithischian family tree, have quill-like structures on at least part of their bodies.
This potentially pushes the origin of quilly structures in Dinosaurs even further. It now appears that the most recent common ancestor of Ornithischia and Saurischia (the first Dinosaur) had fuzzy wuill-like structures on at least part of its body, and likely passed that trait down to its descendants.
How can we make this jump? That's where Occam's Razor comes in. You may be thinking it could be possible that quilly structures in all these different Dinosaur lineages are actually not homologous, and evolved totally independently of each other. However, Occam's Razor tells us that the simplest answer to a question is the one most likely to be correct. Maximum Parsimony as it applies to Phylogenetics explains that the Phylogenetic Tree which involves the least evolutionary change is the most likely to be correct. Using these lines of logic, It is now believed, based on the above evidence, that the very first Dinosaur had quill like structures on at least part of its body, and passed that trait on to its descendants.
Also worthy of mention are Pterosaur pycnofibers, because they too are quill like structures. Current thinking suggests that Pterosauria and Dinosauria are close relatives. This could possibly mean that the most recent common ancestor of both the Pterosaurs and Dinosaurs (Avemetarsalia) may have had some sort of quill structure too. Perhaps even more interesting is the presence of feather-building genes in Alligators, because this could potentially mean that the most recent common ancestor of Crurotarsi (Crocodilians and their extinct relatives) and Avemetarsalia also had quills, meaning that fuzziness was the ancestral condition of all Archosauria, which would be a huge deal if it could be proven to conclusively be the case. For starters, it would mean that any Archosaur that is scaly would be secondarily without fuzz, which has interesting implications for the topic of feather evolution.
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