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Silversoul
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Are birds dinosaurs?
#4731528 - 09/29/05 12:16 PM (18 years, 5 months ago) |
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I've been looking it up, and I seem to get conflicting answers. Some say that they branched off from dinosaurs, while others claim that there doesn't seem to be any clear line between them, and thus they actually are living dinosaurs. Which is it?
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lowdominion
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Re: Are birds dinosaurs? [Re: Silversoul]
#4732573 - 09/29/05 04:11 PM (18 years, 5 months ago) |
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I would say the dinosaurs are direct ancestors of birds from what i have read of fossil evidence
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Silversoul
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Re: Are birds dinosaurs? [Re: lowdominion]
#4732895 - 09/29/05 05:41 PM (18 years, 5 months ago) |
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But several dinosaurs appear to have had feathers. What is the cutoff point where avians ceased to be dinosaurs?
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Catalysis
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Re: Are birds dinosaurs? [Re: Silversoul]
#4733379 - 09/29/05 07:36 PM (18 years, 5 months ago) |
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Quote:
Paradigm said: But several dinosaurs appear to have had feathers. What is the cutoff point where avians ceased to be dinosaurs?
I would assume about the same time that the environment became uninhabitable for the megaflora and megafauna. At one time, the state of the world was such that a human would feel dwarfed compared to the size of the plants and animals. After the extinction, much smaller animals ruled the planet.
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Silversoul
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Re: Are birds dinosaurs? [Re: Catalysis]
#4733661 - 09/29/05 08:43 PM (18 years, 5 months ago) |
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Quote:
Catalysis said:
Quote:
Paradigm said: But several dinosaurs appear to have had feathers. What is the cutoff point where avians ceased to be dinosaurs?
I would assume about the same time that the environment became uninhabitable for the megaflora and megafauna. At one time, the state of the world was such that a human would feel dwarfed compared to the size of the plants and animals. After the extinction, much smaller animals ruled the planet.
Surely you don't define dinosaurs by their size?
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pshawny
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Re: Are birds dinosaurs? [Re: Catalysis]
#4733832 - 09/29/05 09:21 PM (18 years, 5 months ago) |
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di?no?saur ( P ) Pronunciation Key (dn-s?r) n.
1. Any of various extinct, often gigantic, carnivorous or herbivorous reptiles of the orders Saurischia and Ornithischia that were chiefly terrestrial and existed during the Mesozoic Era.
2. A relic of the past: ?living dinosaurs of the world of vegetation? (John Olmsted).
3. One that is hopelessly outmoded or unwieldy: ?The old, big-city teaching hospital is a dinosaur? (Peggy Breault).
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newuser1492
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Re: Are birds dinosaurs? [Re: pshawny]
#4733859 - 09/29/05 09:26 PM (18 years, 5 months ago) |
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Semantics to the rescue.
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Silversoul
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Re: Are birds dinosaurs? [Re: newuser1492]
#4733871 - 09/29/05 09:30 PM (18 years, 5 months ago) |
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http://en.wikipedia.org/wiki/Dinosaur
Quote:
There is an almost universal consensus among paleontologists that birds are the descendants of theropod dinosaurs. Using the cladistic definition (all descendants of a single common ancestor), modern birds are dinosaurs, and dinosaurs are therefore not extinct:
"Ask your average paleontologist who is familiar with the phylogeny of vertebrates and they will probably tell you that yes, birds (avians) are dinosaurs. Using proper terminology, birds are avian dinosaurs; other dinosaurs are non-avian dinosaurs, and (strange as it may sound) birds are technically considered reptiles." ?DinoBuzz, hosted by University of California Museum of Paleontology
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Catalysis
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Re: Are birds dinosaurs? [Re: Silversoul]
#4738552 - 09/30/05 07:57 PM (18 years, 5 months ago) |
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Quote:
Surely you don't define dinosaurs by their size?
No, i just assume that it was probably the same conditions that selected for small bird-like dinosaurs which eventually speciated into current avians.
I think its interesting that many avians today are fliers while there are not many instances of wing-like appendages and feathers in dinosaurs (not very close to todays birds anyways). Thats why the discovery of archaeopteryx was such a big deal. This leads me to believe that, while many dinosaurs shared characteristics of contemporary avians, common birds have only descended from a very limited number of species of dinosaurs.
I think this shows that the Great Extinction was specifically selective for winged, feathered dinosaurs which were probably not unlike birds today.
That is my professional, uninformed arm-chair paleontologist position.
Edited by Catalysis (09/30/05 08:08 PM)
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Silversoul
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Re: Are birds dinosaurs? [Re: Catalysis]
#4738600 - 09/30/05 08:16 PM (18 years, 5 months ago) |
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Quote:
Thats why the discovery of archaeopteryx was such a big deal. This leads me to believe that, while many dinosaurs shared characteristics of contemporary avians, common birds have only descended from a very limited number of species of dinosaurs.
I do not dispute that the vast majority of dinosaurs died out. Most archaeologists agree that modern birds are descended from a small group of theropod dinosaurs. That does not discount the idea that birds are modern theropods, which are a group of dinosaur.
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Catalysis
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Re: Are birds dinosaurs? [Re: Silversoul]
#4738678 - 09/30/05 08:43 PM (18 years, 5 months ago) |
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Quote:
That does not discount the idea that birds are modern theropods, which are a group of dinosaur.
No, it supports that idea. However, from what I have seen, that conclusion is based mostly on skeletal morphology. I think that is a good hypothesis but I would like to see more fossils of transitional species if that were the case. Archaeopteryx is said to have a coelurosaur-like structure (think velociraptor) but coelurosaurs distinctly lack important bird-like features. I just think its difficult to directly link T-rex (theropod) to a hummingbird.
I don't think one can discount parallel evolution to some degree. Many species, some totally unrelated, have bird-like morphological structures (look at squid beaks and bird beaks) yet they evolved totally seperate from each other. I think that birds evolved from a VERY limited number of species (specie?) and that is why we have trouble finding transitional fossils.
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YidakiMan
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Re: Are birds dinosaurs? [Re: Catalysis]
#4744819 - 10/02/05 10:04 AM (18 years, 5 months ago) |
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My geo prof said some dinos hatched with down feathers.
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GulGen
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Re: Are birds dinosaurs? [Re: YidakiMan]
#4746682 - 10/02/05 08:11 PM (18 years, 5 months ago) |
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Why must a line be drawn?
Biological classifications are entirely artificial, creating by humans for our own convenience. You seem to be suggesting that there's some meaningful difference between "they were dinosaurs that evolved into something else" and "they were dinosaurs and have evolved, yet remain dinosaurs".
I'm genetically different from my parents. Should I be considered my own unique species? I'm even more different from my grandparents. And 1000 generations up. And a million. I'm really different from my single-celled ancestors. You can't just draw a line and say that my lineage became humans 1274 generations ago.
And if you want to have more fun, am I an ape? I am certainly descended from apes, but I am also descended from amphibians, and I don't think it fair to call me an amphibian. I think that's really what it comes down to. The term amphibian is no longer applicable to me, even if I am descended from them. I suspect you'd get a lot of debate on whether humans should be considered apes, and it's pretty similar to whether birds are dinosaurs or not. If it can be accepted that the ancestry is there, the question just becomes whether "dinosaur" is still a meaningful term.
Personally, I say call them birds.
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Colonel Kurtz Ph.D
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Re: Are birds dinosaurs? [Re: GulGen]
#4755044 - 10/04/05 03:42 PM (18 years, 5 months ago) |
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Very interesting topic indeed. I mostly concur with Catalysis' opinions. However I'd say that avians should be now considered a different branch of species on the tree of life, since after the cretacic extinction only a few species (if not only one!) survived and developed into what I'd dare call proto-avians, thus creating a lot of species from just a few in a bottleneck fashion, in which their descendents inherited their innate qualities (feathers, smaller size and distinct bone structure) while the qualities that moslty defined dinosaurs faded away to a certain degree. IMO this should be the point where the line should be drawn, but of course, Gulgen is absolutely right when he says that biological classifications are artificial
Just my .02
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Colonel Kurtz Ph.D
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I was just browsing some archeopterix sites and I feel this article may shed some new light into this (old, I know) discussion.
"Archaeopteryx + modern birds, just variation within kind?" http://www.talkorigins.org/faqs/archaeopteryx/info.html#Variation
I hope you guys find it interesting.
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Phluck
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Re: Are birds dinosaurs? [Re: Catalysis]
#4827475 - 10/19/05 10:34 PM (18 years, 5 months ago) |
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Quote:
No, it supports that idea. However, from what I have seen, that conclusion is based mostly on skeletal morphology. I think that is a good hypothesis but I would like to see more fossils of transitional species if that were the case. Archaeopteryx is said to have a coelurosaur-like structure (think velociraptor) but coelurosaurs distinctly lack important bird-like features. I just think its difficult to directly link T-rex (theropod) to a hummingbird.
That's not all the evidence, check this out: http://www.timeforkids.com/TFK/class/wr/article/0,17585,107994,00.html
Quote:
The remains of the young dromaeosaur, revealed last week by the team of Chinese and American paleontologists who studied them, are the clearest link ever between birds and dinosaurs. The specimen boasts the best-preserved body covering of several birdlike dinosaur fossils found in recent years. It shows at least three different kinds of feathers, from head to tail.
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