NationStates Jolt Archive

The Question: Did Birds evolve from Dinosaurs(Most common hypothesus being Therapods), did they follow a strikingly similar evolutionary path? State you position, or is there some other reason? State you position and give evidence as to why.

Also, I do not want this to turn into "Evolution vs. Creationism". You are welcome to bring any thought on this issue forward, but don't turn this into an evo vs. crea thread.

The Question: Did Birds evolve from Dinosaurs(Most common hypothesus being Therapods), did they follow a strikingly similar evolutionary path? State you position, or is there some other reason? State you position and give evidence as to why.

Also, I do not want this to turn into "Evolution vs. Creationism". You are welcome to bring any thought on this issue forward, but don't turn this into an evo vs. crea thread.
It would seem so. Years ago, it was suspected that a few species of dinosaurs may have had feathers, and that pterodachtyls (sp?) were ancestors to modern-day birds, but if I recall, it was recently proven that several (if not possibly all?) dinosaurs were feathered. I'm not sure about any of this, though. I'm just saying what I think I may have heard.

It would seem so. Years ago, it was suspected that a few species of dinosaurs may have had feathers, and that pterodachtyls (sp?) were ancestors to modern-day birds, but if I recall, it was recently proven that several (if not possibly all?) dinosaurs were feathered. I'm not sure about any of this, though. I'm just saying what I think I may have heard.

It is unlikely that Pterodactyls are ancestors to birds. Although both fly, and appear similar on the exterior, their interior structure are vastly different, and how they fly is completely different. Birds fly using a flapping motion similar to swimming, and use feathers to gain lift. Pterodactyls instead probably glided on the air, had wings made of leathery stretched skin, and used straight up and down motions to gain lift.

The most accepted idea is that birds evolved from small Therapods(Tyrannosaurus Rex, the various Dromaeosaurs-Velociraptor and such- are types of Therapods), as birds and therapods share many distinct characteristics, such as hollowed bones and the "S" shaped neck. Also, as you pointed out, the recent discovery of feathered Dinosaurs(Many of which therapods) does provide evidence of such an evolutionary path.

It is unlikely that Pterodactyls are ancestors to birds. Although both fly, and appear similar on the exterior, their interior structure are vastly different, and how they fly is completely different. Birds fly using a flapping motion similar to swimming, and use feathers to gain lift. Pterodactyls instead probably glided on the air, using straight up and down motions to gain lift. Think bats.

The most accepted idea is that birds evolved from small Therapods(Tyrannosaurus Rex, the various Dromaeosaurs-Velociraptor and such- are types of Therapods), as birds and therapods share many distinct characteristics, such as hollowed bones and the "S" shaped neck. Also, as you pointed out, the recent discovery of feathered Dinosaurs(Many of which therapods) does provide evidence of such an evolutionary path.
Hey, I admitted I didn't know what I was talking about!

Hey, I admitted I didn't know what I was talking about!

Lol, didn't mean to sound condescending or anything like that. Just giving some general information.

Between known "link" fossils like the feathered and probably slightly flighted Archaeopteryx and the similarity of bone structure (see, for example, the construction of the hip joints in various species), it seems more than likely that birds are descended from the therapods. Kind of nifty, really, to think that the cute little hummingbird sipping from my feeder might be a great-to-the-nth-power grandchild of T. rex! :)

Between known "link" fossils like the feathered and probably slightly flighted Archaeopteryx and the similarity of bone structure (see, for example, the construction of the hip joints in various species), it seems more than likely that birds are descended from the therapods. Kind of nifty, really, to think that the cute little hummingbird sipping from my feeder might be a great-to-the-nth-power grandchild of T. rex! :)

Or at the very least have the T-rex as a great-to-the-nth-power uncle. Really, some dinosaurs may not have died out. They may still be living in your back yard. Which would be cool to think, would it not?

There's no dispute that bird evolved from dinosaurs- the archaeopteryx being the common ancestor.

http://www.damisela.com/zoo/photo/cq4/archaeopteryx.jpg

Please note that pteradactyls were not birds but flying reptiles. However it did not contribute to the evolution of birds, unlike the more terrestrial reptiles.

It is believed that the archaeopteryx lived amongst the trees and glided, rather than flew. It's bones weren't hollow like today's birds. It managed to retain front claws, scaly skin (feathers yet to be perfected) and teeth. The kiwi from New Zealand proves the bird-reptile like as it retains a tiny vestigial claw at it's wingtip (it's inability of flight probably played a part).

The kiwi from New Zealand proves the bird-reptile like as it retains a tiny vestigial claw at it's wingtip (it's inability of flight probably played a part).
Little know fact, with that claw the kiwi can bring down alligators! It can pierce the strongest steel and combined with the mighty power of its wings the kiwi is a force to be reckoned! And i didnt even mention how its terrible beak fells trees with a single blow!
Fear the mighty kiwi! Run and hide, for if it gets you slaughter will ensue! :D

Little know fact, with that claw the kiwi can bring down alligators! It can pierce the strongest steel and combined with the mighty power of its wings the kiwi is a force to be reckoned! And i didnt even mention how its terrible beak fells trees with a single blow!
Fear the mighty kiwi! Run and hide, for if it gets you slaughter will ensue! :D

Shut your goddamn piehole, kid! You do not insult my national icon!

The only ratite with a mighty kick is a cassowary (a native of Papua). And yes, one kick can kill a human (if a major vein is severed). Zoo keepers need umbrellas to shield themselves if they dare venturing into it's cage and one kick can easily puncture the umbrella fabric.

Well, evidence as of now is really in favour of the dinosaur-bird hypothesis (specifically, since there's a multiplicity of morphological features they share).

Regarding feathered Dinosaurs, there's a number of groups which are now known to have been feathered:

- Dromaeosaurs (Deinonychus, Velociraptor etc. - morphologically closest to Archaeopteryx)
- Oviraptoroids (note that they were not really 'egg thieves' - instead they were brooding their eggs!)
- Therizinosaurs (A previously enigmatic group which is now thought to be closely related to Oviraptoroids)
- Tyrannosaurs (yes, as funny as the idea sounds!)
- Alvarezsaurs (a tiny engimatic group which might be either flightless birds or odd dinosaurs)

There's two other groups (the Ornithomimids and the Troodontids), which (by our current understanding of cladistics) are closely related with the above groups and hence might have feathers as well, but evidence is not known as of now. If you take any other groups of Dinosaurs (either the other theropod-kin like Allosaurs or Ceratosaurs - or any non-theropods), they most certainly NOT had feathers.

I should add though that while this is the best supported hypothesis on the origin of birds, it's not the only one. Also, as of now there is a catching point in this, namely that Archaeopteryx comes from the late Jurassic while any of the feathered Dinosaurs are all early Cretaceous or younger. So, according to that we should find more fossils of feathered Dinosaurs from the middle to late Jurassic some time.

Regarding other hypotheses, support is much scarcer, but i'm going to mention them here anyways for completeness:

The first one is the crocodile-bird hypothesis, which is based on both some morphological as well as genetic similarities. However, any of these similarities should be expected in the dinosaur/bird hypothesis as well, since crocodiles and dinosaurs are not very distantly related.

Next would be the Protoavis hypothesis is based on a single and rather incomplete find from the late Triassic of Texas. The material was highly disarticulated and it's not even certain it was from the same animal. If Protoavis is really as birdlike as it seems, then birds may have branched of from Dinosaurs much earlier than thought.

The last, and least likely hypothesis is the mammal/bird hypothesis, which is based on similarities of certain proteine structures - however these are probably mere convergences that evolved independently due to the fact that both birds and mammals are warm-blooded. It is also morphologically impossible that birds are descended from mammals - differences are simply too great.

So, after all it's most likely birds indeed evolved from (specific) dinosaurs.

Well, Democrats have turned into dinosaurs, and Bush has turned into a bird... (hey, you said I could bring anything up as long as it didn't turn into an evo vs. creation thread).

If you take any other groups of Dinosaurs (either the other theropod-kin like Allosaurs or Ceratosaurs - or any non-theropods), they most certainly NOT had feathers.

So what's your opinion on the integument found on a specimen of Psittacosaurus in the Yixian formation?

Most dinosaurs weren't very big.
Of course we're always impressed by the mega-fauna (either super-dinosaurs or later, giant mammals).
New fossils were discovered recently, that point to an evolution of the bones towards a "ultra light skeleton" even before the animals had feathers. It would make sense for small dinosaurs living on thin trees and vines.

The Question: Did Birds evolve from Dinosaurs(Most common hypothesus being Therapods), did they follow a strikingly similar evolutionary path? State you position, or is there some other reason? State you position and give evidence as to why.

Also, I do not want this to turn into "Evolution vs. Creationism". You are welcome to bring any thought on this issue forward, but don't turn this into an evo vs. crea thread.
in the one of the systems of taxonomy i study, birds are a subgroup of dinosaurs. so it's not that they evolved from them, it's that they are them, in my opinion.

It is unlikely that Pterodactyls are ancestors to birds. Although both fly, and appear similar on the exterior, their interior structure are vastly different, and how they fly is completely different. Birds fly using a flapping motion similar to swimming, and use feathers to gain lift. Pterodactyls instead probably glided on the air, had wings made of leathery stretched skin, and used straight up and down motions to gain lift.

The most accepted idea is that birds evolved from small Therapods(Tyrannosaurus Rex, the various Dromaeosaurs-Velociraptor and such- are types of Therapods), as birds and therapods share many distinct characteristics, such as hollowed bones and the "S" shaped neck. Also, as you pointed out, the recent discovery of feathered Dinosaurs(Many of which therapods) does provide evidence of such an evolutionary path.

Don't forget Archaeopteryx...

Also while it is certain the Therapods were the source of the line to create birds, the Maniraptora group of Therapods is the clear source, to be more specific, like the Dromaesaurs, Troodontids, and Therizinosaurs; as opposed to Coelurosauria like the T-Rex...

So what's your opinion on the integument found on a specimen of Psittacosaurus in the Yixian formation?

Psittacosaurus? A ceratopsian with integument?!? Link, please... :eek:

Btw, my interpretation is that the most parsimonious interpretation would be that this is something the Psittacosaurs developed independently, considering how many other dinosaur groups certainly not had integument of any kind.

I went to the feathered dinosaurs exhibit at the ROM just a couple of weeks ago. It's very interesting and the new fossils seem a pretty good indication that at least one branch of dinosaurs evolved into birds.

Psittacosaurus? A ceratopsian with integument?!? Link, please... :eek:

It's briefly mentioned on page 6 of this link (http://www-hsc.usc.edu/~cmchuong/2003JEZAdapt.pdf). The original paper that it was described in was Mayr et al., 2002.

The integument itself consisted of quill-like structures found on the tail.

Btw, regarding the "Dinosaurs evolved from birds" choice, actually it's not impossible in the case of certain dinosaurs. There exists one hypothesis that suggests that Dromaeosaurs, Oviraptoroids and Therizinosaurs are actually (very primitive) secondarily flightless birds. Evidence is too scarce as of now to say wether this really was the case or not... :confused:

Btw, regarding the "Dinosaurs evolved from birds" choice, actually it's not impossible in the case of certain dinosaurs. There exists one hypothesis that suggests that Dromaeosaurs, Oviraptoroids and Therizinosaurs are actually (very primitive) secondarily flightless birds. Evidence is too scarce as of now to say wether this really was the case or not... :confused:
To be more accurate, this idea, originally proposed by Paul, postulates that the Maniraptora branch is secondarily flightless, not that they are descended from birds. Paul's view is that Archaeopteryx is not a bird, but rather a volant maniraptoran. (This isn't as outlandish as one might think. Omnivoropteryx sinousaorum, Cryptovolans pauli, and Microraptor gui are all known to be flying animals.)

It's briefly mentioned on page 6 of this link (http://www-hsc.usc.edu/~cmchuong/2003JEZAdapt.pdf). The original paper that it was described in was Mayr et al., 2002.

The integument itself consisted of quill-like structures found on the tail.

Thanks.

Well, my impression is that - considering how distantly Psittacosaurus is related with the Theropods, it's more likely that this integument evolved independently. Also, from what i can say they don't have much in common with feathers. Nontheless, this may indeed be one of the first steps in how feather (or integument in general) starts.

Totally unrelated, some of the Pterosaurs had integument as well.

To be more accurate, this idea, originally proposed by Paul, postulates that the Maniraptora branch is secondarily flightless, not that they are descended from birds. Paul's view is that Archaeopteryx is not a bird, but rather a volant maniraptoran. (This isn't as outlandish as one might think. Omnivoropteryx sinousaorum, Cryptovolans pauli, and Microraptor gui are all known to be flying animals.)

Yeah, point there. However, this doesn't change the fact that the bulk of the dinosaurs had little to do with birds in respect for relationship (considering Ornithischia and Sauropodomorphs branched of already in the Triassic).

Guys, you've lost me (and most readers) along the way...

But it's pretty cool. A few Google searches will help me learn that new stuff. :p

in the one of the systems of taxonomy i study, birds are a subgroup of dinosaurs. so it's not that they evolved from them, it's that they are them, in my opinion.

Both reptiles and birds lay eggs, so that's also a link.

Both reptiles and birds lay eggs, so that's also a link.

Well, that's not specific enough to base off of.... (There are mammals which lay eggs...)

Well, that's not specific enough to base off of.... (There are mammals which lay eggs...)

Placentals evolved from the monotremes, which themsleves are a relic of the reptile past.

Well, that's not specific enough to base off of.... (There are mammals which lay eggs...)

and mammals evolved from things known (oddly enough) as mammal-like reptiles.

Placentals evolved from the monotremes, which themsleves are a relic of the reptile past.

Yes, but "laying eggs" is not specific enough to derive descent....

Arthropods lay eggs, and so do many vertibrates; but while sharing "common ancestry"; the vertibrates are not descended from Arthropods, but from Molluscs.... Just saying that general an attribute is not enough to base descent from....

*bump* (cool thread)

Yes, but "laying eggs" is not specific enough to derive descent....

Arthropods lay eggs, and so do many vertibrates; but while sharing "common ancestry"; the vertibrates are not descended from Arthropods, but from Molluscs.... Just saying that general an attribute is not enough to base descent from....

Actually, vertebrates are not descended from Molluscs, they are descended from Hemichordates, whith Echinoderms as an outgroup (Deuterostomes, anyone?).

Yes, but "laying eggs" is not specific enough to derive descent....

Laying calcified eggs is. Only dinosaurs and birds do that.