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Dinosaur Confusion

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Dinosaur Confusion

Postby David George » Wed Mar 01, 2006 10:58 am

Most of us know archaeopteryx.We might be confused if we see a microraptor,avimimus,Caudipteryx and other dinosaurs because these dinos have feathers we might assume that archaeoptreyx evolved from one of these organisms.But we must know that all the above mentioned dinos existed after archaeoptreyx and so they might not related.But these dinos might have become extinct as these could not evolved into birds as there can be only one common ancestor for the birds.
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Postby alextemplet » Thu Mar 02, 2006 12:03 am

I think it's possible that some other dinos might have evolved into birds alongside Archaeopteryx. It's very hard to tell exactly what turned into what 150 million years ago when there's so many possible ancestors. But that's just my opinion.
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Postby flint » Thu Mar 02, 2006 2:11 am

Archaeopteryx is not thought to be an ancestor of modern birds. Supposedly there were two distinct orders of birds when they first came to be - the Enantiornith (sp?) line (Archaeopteryx goes here) and the Modern Bird line (Liaoningornis is the earliest known bird from this line I believe). All enantiorniths went extinct during the mass extinctions 65MYA, but the modern bird line survived (shorebirds most likely survived the extinctions and gave raise to the modern birds we see today). Almost all non-passerine birds exploded into existence shortly after the mass extinctions, with the passerines first showing up about 20MYA (crows, jays, and their family may have come about earlier in Australia).

There is no convincing evidence that any animals other than birds have ever had feathers.
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Postby alextemplet » Thu Mar 02, 2006 2:13 am

Dinosaur fossils have been found with imprints of feathers in the rock surrounding the bones. These imprints are almost identical to those found in bird fossils. That's pretty convincing evidence if you ask me. There are some scientists who think dinosaurs and birds should be classified together. I think that's a little extreme; I believe dinosaurs should be in a class of their own, distinct from both reptiles and birds.
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Postby flint » Thu Mar 02, 2006 2:21 am

Dino fuzz is often mistaken for feathers, and due to the similarity between ceolurosaurs and early birds (imagine an Archaeopteryx without feathers... anyone would call that a ceolurosaur) what is often mistaken as a feathered dinosaur is often a secondarily flightless bird. Im not saying that theres no way that anything but a bird has ever had feathers, but there is no convincing evidence as of now that dinosaurs ever had feathers.
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Postby alextemplet » Thu Mar 02, 2006 2:38 am

Here's a pic published by Berkeley University. What do you suppose this is if not feathers? We know dinosaurs and birds are very closely linked, so it's very probable that some dinosaurs had feathers. Dinosaurs are only distantly linked with mammals so it's very improbable that this is hair. Also, how do you tell the difference between a dinosaur and a primitive bird? Many dinosaurs had a lot of bird-like features, including arm bones almost identical to those in bird wings, feathers, hollow bones, etc. It's very hard to tell one from the other. Anyway, if you want to see more a brief google search should turn up plenty. That's how I found this pic.
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Postby flint » Thu Mar 02, 2006 4:54 am

What do you suppose this is if not feathers?


It can be a lot of things. This isn't the first time someone has billed the fossil of a dinosaur as having "feathers" without the proof to back it up. When the Chinese stumbled across their finds of "feathered" dinosaurs a team of experts was sent to determine if thats actually what was discovered, headed by John Ostrom. Turns out the fossils did not have true feathers, but long fibers that lack the branching patterns of feathers - which is what I would wager the case is in the picture you have shown. It could also be a dendrite, which is a mineral crystal that appears to be a feather in the fossil records.

Also, how do you tell the difference between a dinosaur and a primitive bird? Many dinosaurs had a lot of bird-like features, including arm bones almost identical to those in bird wings, feathers, hollow bones, etc. It's very hard to tell one from the other.


Thats a big problem with this argument for both sides. There really is no good place to draw the line between dinosaurs and birds. Birds probably should be classified as dinosaurs, and Im confident in saying that before I die they will be. However, true feathers are diagnostic for birds. If a vertebrate has feathers it is a bird, and thats where I draw the line.
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Postby David George » Thu Mar 02, 2006 7:30 am

As far as I am considered The biggest mystery is the evolution of beak.I know that changes in
this gene called BMP can change the size and shape of beaks.It is uncertain how they evolved beaks
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Postby David George » Thu Mar 02, 2006 7:33 am

The dromaeosaur group,tyrannosauroid group and also species related to ornithomimus are suspected to be ancestors of modern birds.
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Postby Beetle » Thu Mar 02, 2006 11:10 am

flint wrote:Birds probably should be classified as dinosaurs, and Im confident in saying that before I die they will be.


It is rather bold and scientificaly unsupported to say something like that since you could die, well, right about NOW. :twisted:
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Postby alextemplet » Thu Mar 02, 2006 11:37 am

quote = flint

It can be a lot of things. . . . Turns out the fossils did not have true feathers, but long fibers that lack the branching patterns of feathers - which is what I would wager the case is in the picture you have shown.


Okay, I understand now. Just one question: Do you think it's possible that these might be a more primitive form of feather that doesn't have the branching pattern we're used to? I ask this because we know that dinosaurs evolved into birds, and scales obviously can't turn into feathers overnight, so it makes sense to me for there to be a transitional "semi-feather." Do you think this might be an example?

There really is no good place to draw the line between dinosaurs and birds. Birds probably should be classified as dinosaurs . . . However, true feathers are diagnostic for birds. If a vertebrate has feathers it is a bird, and thats where I draw the line.


I agree with you that there's no good place to draw the line, but I'm not so sure that feathers should be the sole determinant. Not that I can think of anything better, it's just there's some dinosaurs that may have had feathers that I don't think were true birds. But as I've said before I think dinosaurs don't fit well with either reptiles or birds so I think they should be in a class of their own.
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Postby flint » Thu Mar 02, 2006 10:05 pm

It is rather bold and scientificaly unsupported to say something like that since you could die, well, right about NOW.


If it wasnt for the smiley I might take that as a threat!

Okay, I understand now. Just one question: Do you think it's possible that these might be a more primitive form of feather that doesn't have the branching pattern we're used to? I ask this because we know that dinosaurs evolved into birds, and scales obviously can't turn into feathers overnight, so it makes sense to me for there to be a transitional "semi-feather." Do you think this might be an example?


I definitely think its possible. Like you said, the feathers didn't just appear out of nowhere.
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