Quote from: Omegamorph on Jul 18, 2015, 08:18:44 AM
Quote from: Vertigo on Jul 17, 2015, 06:11:46 PM
It used to bug me, because fuzzy tyrannosaurids are still a bit speculative, but having gotten used to the look, I really like them now.
I do support that 'secondarily featherless' theory for the larger, more distal species (Tarbosaurus et al). Who did propose it first?
I don't know who came up with it, but it's made plausible by a few things - first and foremost, scaly skin samples on several tyrannosaurid genera, as you mentioned. Unfortunately there's not the same drive to describe scaly skin, so none of them are particularly solid evidence - some of them are only second-hand references in other studies, others have been informally mentioned but not formally described, and I've seen cases in which hadrosaur skin is passed off as tyrannosaurid.
Anyway, secondly, there have been studies recently which suggest that avian scales are actually feathers, repressed and flattened at the first stage of development. It seems likely that most or all bird scales are secondarily developed, which matches the fossil record as some avialans and dromaeosaurids had feathers/fuzz right down to their feet.
And of course tyrannosaurids had very good reason to lose their fuzz - multi-tonne animals retain body heat with their sheer mass, so they don't need insulatory integument. Almost every tyrannosaurid genus was elephantine in mass, so the group clearly had adaptations specialising in gigantism.
Quote from: MrSpaceJockey on Jul 27, 2015, 07:54:55 PM
Well that's why they lost the legs by modern times. One could say that the legs on Tetrapodophis were pretty much becoming vestigial.
Apparently Tetrapodophis provides evidence that snakes evolved from burrowing lizards, so maybe they lost their limbs when they stopped needing to dig. I wonder if this guy still needed them to clear debris, or for whatever mating behaviour they had at that point. Or, as you say, maybe Tetrapodophis was just part-way to booting limbs out the door.