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Post by sbell on Jan 11, 2009 14:07:07 GMT
^ Very helpful sbell. I've been curious about that for some time, and its going to come in handy one day. Avian and non-avian dinosaurs are so different in so many ways its hard to believe we classify them all as dinosaurs. Then think about what the word 'reptile' means. Ichthyosaurs, plesiosaurs, turtles, dinosaurs, birds, aetosaurs, rauisuchans, paraiesaurs, crocodiles, placodonts, etc. Or tetrapod--all of those, plus 'amphibians' and synapsids (which include mammals + gorgonopsians + pelycosaurs, etc). The fact is, if you go up and down the classifications, they can be very inclusive. For real fun, read Richard Dawkins' The Ancestors' Tale.
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Post by arioch on Jan 11, 2009 17:48:16 GMT
Very good point. Be guided by the physical form or another vague features to classificate organisms is just wrong, since exists something called convergent evolution. In Mesozoic, sauropods filled the niche that elephants fill in the present. Just a matter of adaptation...
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Post by stoneage on Jan 12, 2009 1:12:22 GMT
^ Very helpful sbell. I've been curious about that for some time, and its going to come in handy one day. Avian and non-avian dinosaurs are so different in so many ways its hard to believe we classify them all as dinosaurs. Then think about what the word 'reptile' means. Ichthyosaurs, plesiosaurs, turtles, dinosaurs, birds, aetosaurs, rauisuchans, paraiesaurs, crocodiles, placodonts, etc. Or tetrapod--all of those, plus 'amphibians' and synapsids (which include mammals + gorgonopsians + pelycosaurs, etc). The fact is, if you go up and down the classifications, they can be very inclusive. For real fun, read Richard Dawkins' The Ancestors' Tale. Bell aren't mammals like birds derived from reptiles? We just broke off a little sooner possibly starting with synapsids?
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Post by Tyrannax on Jan 12, 2009 1:20:50 GMT
Birds are sometimes classified under mammals stoneage, but they are their own class.
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Post by stoneage on Jan 12, 2009 2:43:27 GMT
Birds are sometimes classified under mammals stoneage, but they are their own class. ;D What do you mean birds are sometimes classified under mammals? ;D
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Post by sbell on Jan 12, 2009 5:15:44 GMT
Birds are sometimes classified under mammals stoneage, but they are their own class. What on earth are you talking about?
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Post by sbell on Jan 12, 2009 5:21:31 GMT
Then think about what the word 'reptile' means. Ichthyosaurs, plesiosaurs, turtles, dinosaurs, birds, aetosaurs, rauisuchans, paraiesaurs, crocodiles, placodonts, etc. Or tetrapod--all of those, plus 'amphibians' and synapsids (which include mammals + gorgonopsians + pelycosaurs, etc). The fact is, if you go up and down the classifications, they can be very inclusive. For real fun, read Richard Dawkins' The Ancestors' Tale. Bell aren't mammals like birds derived from reptiles? We just broke off a little sooner possibly starting with synapsids? Synapsids are a sister group to the reptiles--share a common ancestor with reptiles at the point of the basal amniotes. The problem lies in the term 'mammal-like reptile' when they are in fact not reptiles at all. It is kind of complicated to write out, but at Wikipedia is a phylogeny that is illustrated based on the Tree of Life project: en.wikipedia.org/wiki/Reptile#PhylogenyThat kind of sums it up better.
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Post by Tyrannax on Jan 12, 2009 6:25:24 GMT
I told you I was bad at explaining things!
Stoneage's original quote:
"Bell aren't mammals like birds derived from reptiles? We just broke off a little sooner possibly starting with synapsids?"
I meant that sometimes when we pick up a book that involves all animals in general, we notice that birds are sometimes classified as mammals. This is not true. Birds are a separate class. You stated birds were mammals stoneage. They are Aves. To be exact they are Kingdom Animalia Phylum Chordata Subphylum Vertebrata Class Aves.
Better?
Unless... you meant to state that birds were derived from reptiles? and not that birds were mammals? You can see how your quote can go both ways.
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Post by sbell on Jan 12, 2009 13:26:11 GMT
I told you I was bad at explaining things! Stoneage's original quote: "Bell aren't mammals like birds derived from reptiles? We just broke off a little sooner possibly starting with synapsids?" I meant that sometimes when we pick up a book that involves all animals in general, we notice that birds are sometimes classified as mammals. This is not true. Birds are a separate class. You stated birds were mammals stoneage. They are Aves. To be exact they are Kingdom Animalia Phylum Chordata Subphylum Vertebrata Class Aves. Better? Unless... you meant to state that birds were derived from reptiles? and not that birds were mammals? You can see how your quote can go both ways. I'm pretty sure he wasn't implying that birds are within Mammalia. THere may be a variety of theories about bird origins, but I don't think that was ever one of them. And I can't think of an instance, ever, where birds were classed with mammals.
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Post by Tyrannax on Jan 12, 2009 18:40:25 GMT
^ I can. Man, I had a book where it actually stated birds were mammals. I knew they weren't, which is why I haven't looked at that book for reference in years.
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Post by stoneage on Jan 12, 2009 22:29:36 GMT
;D What I'm trying to say is that both birds and mammals had reptiles for ancestors. I believe that mammals split from reptiles before the birds. I think Dinosaurs are a transitional phase that at some point lead to birds. The question for me is when did birds branch off from dinosaurs.
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Post by sbell on Jan 12, 2009 22:53:51 GMT
;D What I'm trying to say is that both birds and mammals had reptiles for ancestors. I believe that mammals split from reptiles before the birds. I think Dinosaurs are a transitional phase that at some point lead to birds. The question for me is when did birds branch off from dinosaurs. As the link I posted previously, mammals are within a sister group to 'reptiles'--they share a common ancestor within the basal amniotes; at some point, one of the amniotes developed a temporal fenestra and started the lineage of synapsids; while the other continued without any fenestrae for a while (anapsids) and then some developed two (diapsids) which are the two big groups within the reptiles proper. As for the bird branching--I believe it was somewhere in the Jurassic, but I don't know off hand.
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Post by Tyrannax on Jan 13, 2009 0:08:52 GMT
You are correct sbell, the popular belief is that birds broke of from dinosaurs during the mid Jurassic period.
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Post by [][][]cordylus[][][] on Jan 13, 2009 0:14:35 GMT
Cordylus, Your on the right track, but saying birds are as much dinosaur as we are mammals are two different things. In all honesty, we're as much as mammals as dogs are mammals. And Dinosaurs, being reptiles is not true for birds. Birds are birds. Cardinals are as much birds as humans are mammals. Birds/Dinosaur/Reptile/Fish/Mammals/Etc are all different. Birds stemmed off of Dinosaurs, yes,but Dinosaurs stemmed off of Reptiles. Mammals also stemmed from reptiles. And being human, we are completely mammals, no longer reptiles. Birds are no longer Dinosaurs, but are more stemmed from them into a new class of warm blooded winged animals. I meant to say great apes. ;D
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Post by Tyrannax on Jan 13, 2009 1:00:12 GMT
^ I forgive you, but only because you look so dashing in that hat. ;D
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