Feathered carnosaurs?

[Cross]

Jan 27, 2016 14:20:24 GMT 5 theropod said:

Jan 27, 2016 11:23:34 GMT 5 Cross said:

Are you suggesting that the said specimens of Concavenator and Allosaurus protofeathers which were decomposed upon preservation? 
Because the scales present on both specimens does not resemble the same integument that has room for feathers to grow on other ornithodirans. I.E There don't seem to be any bases for filaments to grow on. The scales appear really compact and resemble those of other dinosaur clades that are known to be scaly, such as hadrosaurids and sauropods (Chiappe et al. 1998; Bell 2013). 



I also found a publication relevant to your statement about taphonomic factors and conditions on feathered and scaly ornithodirans, but this paper only touches the sediments and possible mode of decomposition : www.researchgate.net/profile/Elena_Cuesta/publication/273127149_Taphonomic_study_of_Concavenator_Corcovatus_(Theropoda_Carcharodontosauria)_from_Las_Hoyas_fossil_site_(Lower_Cretaceous_Serrana_de_Cuenca_Spain)/links/54f82d2c0cf2ccffe9dd172a.pdf 

Before preservation, yes. Obviously speed of decomposition is related to surface/volume ratios.

I don't think there are any photographs of the Allosaurus specimen in question. As for Concavenator, we've got evidence of both feathers and scales, yet only the scales were preserved, which I think sort of proves my point.

How do you know hadrosaurs and sauropods didn't have feathers too? Its basically the same situation as with theropods.

Because didn't Chiappe et al. (1998) find an entire nesting site in Auca Mahuevo filled with nests and eggs with sauropod embryos preserved safely inside the eggs, showing that sauropods had tuberculous and visible scales all over their body? 

See : Chiappe, L.M, Coria, R.A (1998) : Embryonic Skin From Late Cretaceous Sauropods (Dinosauria) of Auca Mahuevo, Patgonia, Argentina. Journal of Paleontologyv81(6):1528-1532



I don't think Concavenator preserving both scales and feathers should necessarily be interpreted as evidence that there were feathers along the now-scaly areas of the body that disappeared during decomposition. It just means that the animal was both scaly and had structures homologous to feathers. Kulindadromeus is known from a well-preserved specimen showing that feathers and scales were both present and coexisting on the animal, I don't see why the same cannot be said for Concavenator. 

For the hadrosaurids, see : Bell PR (2012) Standardized Terminology and Potential Taxonomic Utility for Hadrosaurid Skin Impressions: A Case Study for Saurolophus from Canada and Mongolia. PLoS ONE 7(2): e31295. doi:10.1371/journal.pone.0031295

[theropod]

Because didn't Chiappe et al. (1998) find an entire nesting site in Auca Mahuevo filled with nests and eggs with sauropod embryos preserved safely inside the eggs, showing that sauropods had tuberculous and visible scales all over their body?

And is that evidence regarding the presence or absence of feathers in sauropods, especially adults?

For the hadrosaurids, see : Bell PR (2012) Standardized Terminology and Potential Taxonomic Utility for Hadrosaurid Skin Impressions: A Case Study for Saurolophus from Canada and Mongolia. PLoS ONE 7(2): e31295. doi:10.1371/journal.pone.0031295

Similar case here. Proving the presence of scales (which you don’t have to prove, at least not for me) is not the same as disproving the presence of feathers.

I don't think Concavenator preserving both scales and feathers should necessarily be interpreted as evidence that there were feathers along the now-scaly areas of the body that disappeared during decomposition.

It’s currently neither evidence for nor against it. Hence why it would be good to perform an experiment. It appears reasonable to assume that scales have a lower chance of decomposition and thus a higher chance of fossilisation than feathers, the question is how much.

Kulindadromeus is known from a well-preserved specimen showing that feathers and scales were both present and coexisting on the animal, I don't see why the same cannot be said for Concavenator.

The same can be said for Concavenator, in fact it was definitely the case, and is moreover likely to be the case in other cases too. The question is whether scaly areas on Concavenator, or dinosaurs in general, were necessarily devoid of feathers, or were merely scale-dominated with less conspicuous filaments that didn’t get preserved, that’s an entirely different thing.

[Cross]

Jan 28, 2016 16:11:29 GMT 5 theropod said:

Because didn't Chiappe et al. (1998) find an entire nesting site in Auca Mahuevo filled with nests and eggs with sauropod embryos preserved safely inside the eggs, showing that sauropods had tuberculous and visible scales all over their body?

And is that evidence regarding the presence or absence of feathers in sauropods, especially adults?

For the hadrosaurids, see : Bell PR (2012) Standardized Terminology and Potential Taxonomic Utility for Hadrosaurid Skin Impressions: A Case Study for Saurolophus from Canada and Mongolia. PLoS ONE 7(2): e31295. doi:10.1371/journal.pone.0031295

Similar case here. Proving the presence of scales (which you don’t have to prove, at least not for me) is not the same as disproving the presence of feathers.

I don't think Concavenator preserving both scales and feathers should necessarily be interpreted as evidence that there were feathers along the now-scaly areas of the body that disappeared during decomposition.

It’s currently neither evidence for nor against it. Hence why it would be good to perform an experiment. It appears reasonable to assume that scales have a lower chance of decomposition and thus a higher chance of fossilisation than feathers, the question is how much.

Kulindadromeus is known from a well-preserved specimen showing that feathers and scales were both present and coexisting on the animal, I don't see why the same cannot be said for Concavenator.

The same can be said for Concavenator, in fact it was definitely the case, and is moreover likely to be the case in other cases too. The question is whether scaly areas on Concavenator, or dinosaurs in general, were necessarily devoid of feathers, or were merely scale-dominated with less conspicuous filaments that didn’t get preserved, that’s an entirely different thing.

Because feathers cannot grow on areas that are already tightly packed with keratinous texture and scales?
It would take too much energy to have your keratinous skin develop pores and/bases for more keratinous structures to grow. Birds that are born without feathers and develop them throughout ontogeny usually have smooth scaleless skin because feathers require attachment points to grow, and there's no room for that on skin with beta-keratinous scales tightly packed together. I personally think the fact that hatchling sauropods are scaly proves that the adults were also scaly.

The holotype Concavenator[i/] was preserved on one slab of rock. If the supposed ulnar papillae on the posterolateral surface of the ulna really turn out to be feathers, why were those areas the only ones preserving feathers when the other scaly areas were probably preserved and decomposed at the same rate?

[theropod]

Because feathers cannot grow on areas that are already tightly packed with keratinous texture and scales?

Sais who?

Those are clearly feathers growing in between scales (or scuta and scutellae).

It would take too much energy to have your keratinous skin develop pores and/bases for more keratinous structures to grow.

That’s an assumption about feather development that I’m not making, I’m not talking about feathers developing in between scales in these taxa, more likely the opposite, since feathers are likely to have been ancestrally present in one form or another. Ontogenetically they’d probably develop FROM scales. And scales persisting into adulthood, in turn, might be secondarily developed from feathers–that depends on whether scales were lost and then redeveloped at some point as they were in birds.

Birds that are born without feathers and develop them throughout ontogeny usually have smooth scaleless skin because feathers require attachment points to grow, and there's no room for that on skin with beta-keratinous scales tightly packed together.

Those birds have scaleless skin because they haven’t yet developed either structure, not because it’s impossible for feathers to grow on otherwise scaly skin. Integument can very well change during ontogeny, reptiles (such as the sauropods in question) that have osteoderms as adults but not as embryos are equally good demonstration of that as birds that hatch without feathers.

I personally think the fact that hatchling sauropods are scaly proves that the adults were also scaly.

I’m certainly not implying that adult sauropods didn’t have scales too, but what if embryonic scales are a simple ontogenetic recapitulation of a more basal trait, while adults of the taxon bore feathers? Human embryos have gill slits and a tail, that doesn’t prove that adults have them too.

The holotype Concavenator[i/] was preserved on one slab of rock. If the supposed ulnar papillae on the posterolateral surface of the ulna really turn out to be feathers, why were those areas the only ones preserving feathers when the other scaly areas were probably preserved and decomposed at the same rate?

Whose quote? Anyway, I think the explanation is obvious; they were not decomposed equally quickly at all. Given we accept the identification as quill knobs, following the only researchers’ opinion that is backed up by first hand examination of the fossil, that’s even indicative in that regard.
Not proving anything of course, its always possible that some part of the carcass was simply subject to taphonomic conditions favouring integumentary preservation, but still a potential case of what I mean.
Hence my call to test for that further. I’m just sadly a little short on intact samples of reptile skin (and places where I can let them rot in peace) to do it.

[Cross]

Jan 28, 2016 20:12:27 GMT 5 theropod said:

Because feathers cannot grow on areas that are already tightly packed with keratinous texture and scales?

Sais who?

Those are clearly feathers growing in between scales (or scuta and scutellae).

It would take too much energy to have your keratinous skin develop pores and/bases for more keratinous structures to grow.

That’s an assumption about feather development that I’m not making, I’m not talking about feathers developing in between scales in these taxa, more likely the opposite, since feathers are likely to have been ancestrally present in one form or another. Ontogenetically they’d probably develop FROM scales. And scales persisting into adulthood, in turn, might be secondarily developed from feathers–that depends on whether scales were lost and then redeveloped at some point as they were in birds.

Birds that are born without feathers and develop them throughout ontogeny usually have smooth scaleless skin because feathers require attachment points to grow, and there's no room for that on skin with beta-keratinous scales tightly packed together.

Those birds have scaleless skin because they haven’t yet developed either structure, not because it’s impossible for feathers to grow on otherwise scaly skin. Integument can very well change during ontogeny, reptiles (such as the sauropods in question) that have osteoderms as adults but not as embryos are equally good demonstration of that as birds that hatch without feathers.

I personally think the fact that hatchling sauropods are scaly proves that the adults were also scaly.

I’m certainly not implying that adult sauropods didn’t have scales too, but what if embryonic scales are a simple ontogenetic recapitulation of a more basal trait, while adults of the taxon bore feathers? Human embryos have gill slits and a tail, that doesn’t prove that adults have them too.

The holotype Concavenator[i/] was preserved on one slab of rock. If the supposed ulnar papillae on the posterolateral surface of the ulna really turn out to be feathers, why were those areas the only ones preserving feathers when the other scaly areas were probably preserved and decomposed at the same rate?

Whose quote? Anyway, I think the explanation is obvious; they were not decomposed equally quickly at all. Given we accept the identification as quill knobs, following the only researchers’ opinion that is backed up by first hand examination of the fossil, that’s even indicative in that regard.
Not proving anything of course, its always possible that some part of the carcass was simply subject to taphonomic conditions favouring integumentary preservation, but still a potential case of what I mean.
Hence my call to test for that further. I’m just sadly a little short on intact samples of reptile skin (and places where I can let them rot in peace) to do it.

Alright, point well taken. 
Though for the experiment you have in mind, how would we replicate or simulate millions of years of decomposition under controlled conditions? 

[theropod]

Not at all? Soft tissue doesn't take millions of years to decompose. Decomposition isn't the same as diagenesis.

[Cross]

Well, with hadrosauroids, we have a vast number of exceptionally well-preserved specimens of Saurolophus, Edmontosaurus, Brachyolophosaurus, and lots of other taxa known from mummified specimens that seem to indicate that tuberculous and carbonaceous scales appear to have covered pretty much the entire body.

With the Auca Mahuevo sauropod embryos, I think I remember a source finding that feathers cannot grow on scales, but only in-between them. The scales on the Auca Mahuevo sauropod embryos are really tightly spaced along the skin, which doesn't seem to indicate that feathers could have developed around or on top of them.

Why don't you trust the abstract by Pinegar et al. ? I know there are no photographs of the Allosaurus skin patch, but there are no photographs of the large Mapusaurus pubis either, yet the two of us continue to cite its existence when discussing Mapusaurus.
I hope this doesn't sound like an Ad Hominiem-ish argument, all I'm saying is that the observations stated in a scientific paper aren't automatically dubious/not credible just because there are no photographs.

I do strongly think that feathers are ancestral to Ornithodira and maybe Archosauria as a whole, but there is still evidence that some dinosaur groups were dominantly scaly.

[Cross]

Wait, so what do you think is the most parsimonious/reasonable amount of feathery integument on allosauroids? 

Would they have resembled something like this? : 

[creature386]

Kinda depends on where Sciurumimus can be classified. Persons and Currie (2015) still believe it is a megalosauroid, but without presenting a phylogenetic analysis or otherwise replying to Pascal et al. (2013) which classify Sciurumimus as a coelurosaur and can be maybe seen as the most recent study on that issue. In case it was one, these feathers are probably a bit exaggerated, unless the complexity evolved convergently.

[theropod]

Where have I said that I didn’t trust the abstract? It’s not that I don’t, it just doesn’t provide the evidence to claim that filaments in carnosaurs were limited to "minor areas" or that a carnosaur covered in protofeathers was "out of the question".

The core findings: A juvenile Allosaurus with a 30cm² patch of scaly skin being preserved.

Those are relevant details.
If you assume that patch to be circular, that would make it around 6.2cm in diameter–it’s not as if they had found an impression of the entire animal showing that it was completely scaly to begin with, let alone refuted the possibility that there were feathers along with those scales. It is implied, but not explained in much detail, where the patch came from (the "side of the body"). And who knows in what way the juveniles’ integument may have differed from that of adults? So what does this prove? No more and no less than that juvenile allosaurs had scales.

This does little to refute the presence of feathers/filaments, because it is evidence for the presence of one type of integument, but not for the absence of another.

I’ve got no precise opinion on the distribution and prevalence of feathers that we should restore carnosaurs with. The lack of fossil reservation means any statement would be a guess. Anything from a thick filament coating of the dorsum with a visibly scaly ventral side, to a patchy distribution of small filaments in between scales is realistic. I highly doubt carnosaurs lacked filaments alltogether (as I see you agree that feathers are an ancestral trait, so you should get my reasons), and I highly doubt they had structures comparable in complexity to maniraptoran compound feathers (because they didn’t have bird-like skin either), but apart from that, every conceivable combination is consistent with the evidence.

That model doesn’t look so convincing to me though, those spines on its back would be absurdly huge. This is a 6m animal, so we’re talking about spikes several centimetres thick and tremendously strong that somehow didn’t have any discernible skeletal attachments (except for those on the arms), nor, in fact, left any trace on a fossil that preserved keratinous scales on the belly. I wouldn’t call those "filaments" anyway.

[theropod]

Further evidence that the papillae on Concavenator’s ulna aren’t myological in origin, and hence are probably quill knobs:
repositorio.uam.es/handle/10486/678416

[Deleted]

I suppose it’s theoretically possible.