It has been a year since I've made my
, and I think it's time for it to be remade. Some new discoveries have naturally made it obsolete, such as ornithomimid wings and Sciurumimus
(although frankly I'm still skeptical about it being a megalosaur). But before that, I'd like to share some musings of mine.
Firstly, I'm still fond of the idea that primitive feathers are basal to Ornithodira in some way or another, perhaps evolving from dermal spines or something along those lines. But I'm starting to believe that, as wondrous as I find the idea of fuzzy ornitischians to be, extensive coats of feathers were really limited to coelurosaurs.
That's because, up until now, the only confirmed examples of something other than scales in ornitischians come from Psittacosaurus
. I'm sure these are homologous with each other and that primitive ornitichians had bristles as a basal condition, but I'm not so sure if these and coelurosaur feathers were really the same thing. What makes me doubt it is that, while most evidence so far seems to favor the idea that no big coelurosaur totally lost their feathers - the idea of feathered adult Tyrannosaurus
being more accepted now than ever - the confirmed presence of extensive scaly hide in hadrosaurs, stegosaurs, ceratopsians and ankylosaurs just makes it more likely that the bristles of primitive ornitischians weren't the same thing. If they were, why would these derived forms loose it? I'm sure a cover or fuzz would be more advantageous to endothermic megafauna.
The thing is, I don't think the quills on Tianyulong and Psittacosaurus served a thermoregulative function. They could well be another experiment in integument, no doubt arising from the same genetic base as the feathers that later appeared in theropods and earlier in pterosaurs, but they were structurally different and probably used just for show and were much more prone to be lost. I just don't see why every form of derived ornitischian of which we have skin preserved would loose their fuzz if they were the same as theropod feathers - that would contradict everything that has being said about tyrannosaurs and therizinosaurs and moas retaining theirs.
In short, I love the idea of fluffy heterodontosaurids with fur-like feathers all over their bodies, but evolutionarily it doesn't make sense to be, because otherwise hadrosaurs should be as hairy as buffalos. What do you guys think?