Herrerasaurus Skin?

[Loon]

Hello, does anyone have any information of what kind of skin covering(s) Herrerasaurus would have featured? I'm guessing scales, but of what kind, I'm unsure; also, maybe some earlier feathery structures? I'm really unsure.

[ZoPteryx]

It really depends on your gut feeling with regard to the origin of filamentous coverings ("proto-feathers").  As it stands, there are two main possibilities:

1) Filamentous integument arose separately in ornithischians and advanced theropods as a response to increased metabolic rates (or some other aspect of being small and bipedal).  In this scenario, Herrerasaurus would most likely be covered almost entirely in small pebbly scales with maybe some cornified skin around the face.

2) Filamentous integument is ancestral to all dinosaurs, and maybe back to their last common ancestor with pterosaurs.  In this scenario, Herrerasaurus would be covered in a mixture of filaments and scales, probably in a pattern similar to Kulindadromeus* where the tail and lower limbs are scaly and the body, neck, and upper limbs are fuzzy.  Cornified skin would probably still be found around the face.

*And maybe also Juravenator.  If these two taxa from opposite sides of the dino family tree have similar integument patterns (do any pterosaurs fit the theme I wonder?) it could represent the ancestral state for dinosaurs.

I personally would go with the latter, but in the end it's about a 50-50 bet right now.  Mark Witton's recent article on the integument of Plateosaurus may be of interest:
http://markwitton-com.blogspot.com/2016/11/the-blog-post-where-i-ask-myself-should.html

[stargatedalek]

I think the most likely scenario is that soft integument dates back to the early archosaurs. This explains why all three "major" groups display evidence of it among their members. It also explains why so many different kinds of scales are found throughout these groups, the scales were a secondary trait.

Because of this shared common ancestor, archosaurs shared a genetic predisposition towards developing soft integument (as we see evidence of in modern crocodiles). Feathers, pycnofibers, and "Kulindadromeus stuff", are all very different in structure and most likely evolved independently, but at the same time the scales of crocodilians, sauropods, Ceratosauria, and ceratopsians also most likely evolved independently.

Something like Herrerasaurus? Who knows.

[Neosodon]

Herrerasaurus most likely had scales. The oldest therapods to be found with primitive feathers were compsognathids from the Jurassic. But there may be Triassic therapods with feathers waiting to be discovered.

[Papi-Anon]

I'd like to piggyback off this subject of skin and scales.

What of the early reptiles? I find it odd that the transition of moist, thin amphibious skin going to saurian scales instead of a non-sebaceous skin that still locked moisture in the body. Or maybe I'm missing something on the evolution of skin in the earliest amniotes?

[stargatedalek]

I'd like to piggyback off this subject of skin and scales.

What of the early reptiles? I find it odd that the transition of moist, thin amphibious skin going to saurian scales instead of a non-sebaceous skin that still locked moisture in the body. Or maybe I'm missing something on the evolution of skin in the earliest amniotes?

I'd never considered it before. It seems likely that scales didn't evolve until at least after the mammalian ancestors split, but could have appeared even later.

Is it possible at all that dermal covering in fish gave way directly to dermal covering in now extinct amphibian lineages and later reptiles? And the thin skin of modern amphibians was also itself a secondary trait?

[Papi-Anon]

Yeah, makes me wonder if the first 'reptiles' were more like salamanders with moisture-retaining skin and that scales evolved in just the saurapsids with synapsids just carrying the basal skin over to the eventual sebaceous design. Scales becoming feathers, okay, easy to see that transition. But scales to glandular skin, then to hairy skin? I'm having a hard time seeing that evolutionary path.

Then again I'm sure there's been some theories that I haven't heard of yet.

[Halichoeres]

Modern amphibians are secondarily smooth, which is why they're called Lissamphibia ("smooth amphibians"). Early tetrapods were mostly pretty scaly, even some of the temnospondyls, from which lissamphibians were probably derived. BUT the scales of sauropsids are not clearly homologous with those of, for example, lungfishes, fish-apods, or coelacanths.

Scales to glandular skin to hairy skin might be hard to wrap one's head around, but it's almost certainly what happened. If it helps, at some point even sauropsids had to trade in one kind of integument for another, because lizard scales are wildly different histologically from lungfish scales.

As to the original question, I always imagine Herrerasaurus scaly, but I think Witton is right to point out that it's hard to be confident in any particular assumption about its pajamas.