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Re: Are Birds Saurischian?
I'm not a paleontologist, and I don't play one on TV. What follows is my
own, uneducated opinion. So, consider what you paid to get it.
>Looking at the sample cladogram on page 34 of
>the magazine, it looks to me like Archaeopteryx is a saurischian
>dinosaur. If so, is it correct to say that all birds are saurischian
As I understand cladistics, yes. Anything connected to a certain node
carries that name. This includes nodes that come later in the tree, but can
be traced back to that certain node.
1 2 3
\ \ /
\ \ /
\ * Theropoda
where 1=Sauropoda, 2=Dromaeosaurs, 3=Aves (birds)
Everything above Dinosauria is in the Dinosauria, everything above
Saurischia is in the Saurischia, everything above Theropoda is in the
Theropoda. Therefore number 3, Aves, is a member of Theropoda AND
Saurischia AND Dinosauria. However, number 1, Sauropoda, is only in the
Saurischia and Dinosauria since it branches off before the Theropoda.
Note: this is an example of a cladogram, and not intended to be mistaken
for the actual Dinosaurian cladogram.
>(I suppose what I'm asking is: If birds are dinosaurs, are
>they a third basic group, or are there still only saurischians and
>ornithischians, and birds belong completely in the former?)
Birds are considered saurischians, specifically Theropods, under cladistics.
>And if birds
>ARE saurischians, then only ornithischian dinosaurs became extinct, right?
Now, if somebody adhere's to Linnean groupings, the answer to whether
birds are dinosaurs might be different. However, from what I understand,
many paleontologists would consider birds dinosaurs even under Linnean
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