The dinosaur thread

I'd put money on the fact that various forms of feathers were found in a lot more species than is currently estimated.

x6 More that Aves is a lineage of maniraptors.

x3 Yep, those people are a fringe group who don't have a leg to stand on. Their "research" regarding bird origins is essentially pseudoscience.

And yes, it does look likely that feather-like structures were fairly widespread and possibly ancestral among dinosaurs.

Albert: Ooh, right. :o

And neat! :3

ᐅᖃᐅᓯᖅ ᐊᑕᐅᓯᖅ ᓈᒻᒪᔪᐃᑦᑐᖅ

Pff, when I was a kid, dinosaurs were reptiles and Pluto was a planet.

"I don't know how I do it. I'm like the Mr. Bean of sex." -Drunkscriblerian

Pfft, newcomer. When I was a kid, there were only five elements.

ᐅᖃᐅᓯᖅ ᐊᑕᐅᓯᖅ ᓈᒻᒪᔪᐃᑦᑐᖅ

No dinosaur-naming experts around here, huh?

Wait, you mean the paeleontologist community has changed its mind about "dinosaurs are reptiles"? Since when, and what is the new classification?

edited 9th Jun '12 8:33:12 PM by MarqFJA

Fiat iustitia, et pereat mundus.

Both are ornithischian (bird-hipped) dinosaurs. Despite what the name would have you think, birds did not evolve from ornithischians, but rather saurosichians (lizard-hipped). Also, IIRC, skin impressions have been discovered of Triceratops that showed it had rough, scaly skin. However, Triceratops did have an ancestor called Psittacosaurus which did have featherlike filaments on its tail.

Dinosaurs are still reptiles. It's just that they are viewed as being very unique for reptiles, being warm-blooded and leading active lifestyles and the like. This has, in fact, been accepted fact since The '60s. It just hasn't permeated into pop culture until Jurassic Park.

edited 9th Jun '12 9:01:47 PM by RLNice

A fistful of me.

Huh. :o That's interesting. And the apatosaurus? :o

And yeah, I thought dinsaurs were still reptiles. Says right here at least.

ᐅᖃᐅᓯᖅ ᐊᑕᐅᓯᖅ ᓈᒻᒪᔪᐃᑦᑐᖅ

When it comes to the larger dinosaurs, it could be a case of losing the feathers as they go from juvenile to adult. A bit like baby elephants are actually quite fuzzy little things. But, that doesn't last, due to having to radiate heat. Mammoths kept the fuzz, and emphasised it. For obvious reasons.

Rhinos do this, too.

Some medium and larger dinosaurs outside the theropods might actually have had the odd feather-like deal going on in colder climes and not just the smaller ones. For all we know, some actually could have moulted depending on the season.

edited 9th Jun '12 9:31:16 PM by Euodiachloris

I read an article that posited that's what happened with baby tyrannosaurs. Basically, as babies they were these ridiculously cute little things you'd want to cuddle. And then they grew large enough to eat you in one bite.

Okay, here's what's weird. Dinosaurs are said to be reptiles, and birds are said to be dinosaurs, but birds are not said to be reptiles. Why?

I vowed, and so did you: Beyond this wall- we would make it through.

Because people haven't kept up?

Because evolution causes some things to not be in the same genus or whatever as their distant ancestors. Our first ancestors were probably rodents.

Most likely just a case of Science Marches On. Birds have actually been classified as Archosaurs since the 19th century, but for some reason we're now seriously considering them reptiles.

IIRC, most Dinosaurs didn't have feather-like structures or insulation. Pretty much all cases of feathers were found in coelurosaurs and other bird-like theropods, like those Tyrannosaurids in China that were recently discovered. A lot of them were still scaly.

BTW, since not only are Crocodilians archosaurs, we have plenty of fossil evidence that there were once highly active, terrestrial and perhaps warm-blooded creatures in their order as well. Y'think there might have been some crocs with fur-like insulation?

Fuzzy crocs have always been a thing of mine. Brightly coloured fuzzy crocs... heeeeee... Although, I still wouldn't want to meet one in brightest day, let alone a dark night. Particularly not the faster, bigger, meaner versions, thanks.

Like a Nile croc has a good temper at the best of times... not.

The definition of "reptile" is a bit of a mess, if I remember correctly. A term that applies equally to alligators and to turtles but not to birds is bound to cause confusion.

But they seem to know where they are going, the ones who walk away from Omelas.

This, essentially. I don't think most dinosaur paleontologists would have qualms about calling birds reptiles, but it can certainly be confusing to the general public. Some paleontologists advocate using the term sauropsid for the clade including both traditional "reptiles" and birds, keeping "reptile" as an old outdated assemblage of species that don't all form a natural grouping.

x3 Yep, most definitively feathered dinosaurs are coelurosaurs. Extensive scaly skin is known for more basal theropods (e.g.: Carnotaurus), derived sauropods (even embryos), hadrosaurs, ceratopsians, and I think thyreophorans. There are caveats though. If these dinosaurs had only very fine feathers (or similar structures) and/or only on limited parts of the body, most sediments might not preserve them or they might easily have sloughed off prior to being fossilized/forming impressions. (Fur and feathers come off pretty easily from dead animals that have been washed around in the water it appears.) After all, the tail bristles of Psittacosaurus were only restricted to a fairly small region on the top of the tail (as far as we can tell) and the rest of the body was scaly. And even among coelurosaurs there are signs that the more basal species didn't yet have the extensive feathering of maniraptors, for instance. (Scales are known from the tail of some compsognathids and tyrannosauroids, for example, even though there are also compsognathid and tyrannosauroid specimens that have feathers on other parts of the body. Juravenator, which might be a basal coelurosaur or some other type of theropod entirely, is definitively known to have had both scales and feathers on its tail.)

Don't really buy the notion that some theropods completely lost their feathers as the grew, incidentally. Not even elephants lose all their hair as adults, for one thing, and Yutyrannus shows that fairly large theropods could still have had rather thick and extensive plumage. The possibility of young being fluffier than adults is certainly plausible though.

My current guess is that most dinosaurs may not have had an extensive coat of feathers as coelurosaurs do, but some sort of feather-like structure was indeed present in the common ancestor of all dinosaurs, which was independently modified into an insulating coat by some lineages (e.g.: coelurosaurs and heterodontosaurids) and lost by others (e.g.: sauropods). Speculative, of course, but it's the best idea I've heard of that fits what we currently know. We really need some fossilized integument from really basal dinosaurs in the Triassic; those would help a great deal.

Re possibility of feathers in Triceratops and Apatosaurus: There's a yet-to-be-published Triceratops specimen which shows large, bumpy scales. Some reckon these bumps might be attachment points for Psittacosaurus-like bristles. Problem is that Psittacosaurus bristles don't appear to anchor to scales like that, so that doesn't sound too convincing. Best to wait for the paper though.

Apatosaurus is a sauropod, and as noted earlier even very young sauropods appear to have had scaly skin all over. The sauropods that preserve such a condition are very derived titanosaurs though, and there's still the possibility that there were "feathered" sauropods somewhere down the line. But even then, given that most sauropods were gigantic, said "feathering", if present at all, was probably very sparse.

As for croc-line archosaurs potentially having feathers, there's currently no evidence of such but it wouldn't be a huge surprise for me if it turned out to be true. There was a recent online National Geographic article which mentioned in passing that alligators have a gene that's involved making feathers in birds, which is intriguing to say the least.

x4 Uh, not quite. A clade by definition will always include the descendants of a given common ancestor. And although rodents are fairly close to primates as far as modern mammals go (only tree shrews and colugos are closer), our ancestors were never rodents (and so we aren't rodents either).

Hmm, I never knew that the common ancestor of dinosaurs already had feather-like structures for insulation. I always assumed that it just evolved in one of the lineages when they became more metabolically active. Thanks for the info!

I should probably clarify that it's a possibility, not fully confirmed. But it does appear to have a pretty good chance of being true, considering that Tianyulong, an ornithischian (which is about as far from birds as you can get while still remaining a dinosaur), is known to have had a coat of fuzz.

That's interesting. I wonder: how far back do filaments actually go? I mean, if this archosaur, Tianyulong has them, and a fair few (if not, maybe, all) of the pterosaurs... then... uh...

They're not exactly just restricted to one group, are they? Maybe there's a greater history of fuzz that needs exploring? Although, I dare a Palaeontologist to name a book that: The Greater Prehistory of Fuzz doesn't sound so grand, does it?

edited 10th Jun '12 8:10:16 PM by Euodiachloris

That's what we don't know at the moment. The possibility of pterosaur pycnofibers and dinosaur fuzz having a common origin has certainly been considered. Someone should probably do an in-depth comparison between all these different types of filaments and seriously investigate this.

I'm not ever going to rule convergent evolution out... but, for them to have a common base from which to evolve similar structures beyond just labelling it "interesting scales" and moving on seems... a smart thing to seriously look for.

I would be very tempted to put money down on a common ancestor developing just the right (or in this case, the not-exactly-wrong-but-not-exactly-doing-anything) kind of base for the scale that could branch out so much with just minor (or even major) mutations in the switches governing the structures of the endothermic layers in successive generations. The potential might have sat there for donkey's yonks until *boom* the right switches started being shifted.

From an admittedly very cursory look at it, that might be sometime in the early Jurassic. That would make a degree of sense: if anything weird's going to be tripped (or just highlighted), after an extinction event would be the time to expect it. And that particular event has all sorts of weird written all over it.

Not all descendants would have kept that mutation, though, of course. If something just sits there doing nothing for ages, odds are, another mutation with an actual use that supersedes it will occur. But, if the underlying change is still there and dormant, however hidden it might be, it would explain cycles of re-emergence over a diverse number of species over time.

edited 10th Jun '12 10:54:24 PM by Euodiachloris

If fuzz (or potential for it) appeared in the common ancestor of all dinosaurs (or beyond!), it probably evolved in the Triassic, as that's when said common ancestor would have been around.

I might add that actual feathers at least appear to be entirely novel structures, not derived from scales.

Fuzzy Dinosaurs?

Yarp: mammalian claims of epic cuteness due to the funny fuzzy furriness are shot down in flames after years of lording it over everybody. Ain't it grand?

Although... a full-grown carnosaur would have to go some to convince me of innate cuteness. Having said that... big cats: often cute, usually dangerous. Er... maybe I have to rethink that stance? Hmmm: Terror Birds... maybe more of a blast from the past than we give them credit for? <looks at them long and hard to assess for cute> Well, maybe the dino chicks were cute, at least...

@Albertonykus: Thanks. Well, feather-like structures, at least, started kicking off in the Jurassic, then, thanks to that Triassic... whatever it was. Something must have prodded the change from random bits of isolated fluff, an amount of bristle-cover, nothing fantastic to speak of, or full-on fluffy (depending on the 'saur in question) to the later feather dusters. If it ain't the extinction event, I'm going to start marinating my floppy hat.

edited 11th Jun '12 1:25:02 AM by Euodiachloris