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Re: crocodylomorphs?/ birds
>From: "Considine, Blaise" <BPC.APA@email.apa.org>
> 1) what is a crocodylomorph?
It is a member of a subgroup of the archosaurs that are more
or less closely related to the crocodylians.
Crocodylomorphs include crocodyles, and some Triassic and
Early Jurassic terrestrial forms, such as Hesperosuchus.
> 2) so the current theories re birds are 1) they and the dromaeosaurs
> came from the same stock, and branched apart during the early jurassic
Yes, or perhaps branching in the Middle Jurassic.
> 2) dinosaurs are an offshoot from reptiles to birds
I am not sure what this is intended to mean.
Dinosaurs in the traditional sense are believed to be more
or less intermediate between birds and stem reptiles.
> 4) are archaeopteryx and protoavis properly considered birds
Yes and no.
Archaeopteryx is held to be a bird by most workers.
Only two or three people believe Protoavis to have been a
bird, and at least one of those is known to be unreliable
on phylogenetic issues from other suggestions he has made.
>, or are they their own group?
At one level, Archaeopteryx is in its own group - its own
particular subgroup of birds. But it is still more or less
a bird. (Actually it is so close to being exactly intermediate
that placement is difficult).
The proper position for Protoavis in undetermined, at least as
far as I know. I have heard it suggested it is a very early
coelurosaur (modern sense), a crocodylomorph, or a ceratosaur.
I cannot see how to decide which right now, based on Chatterjee's
The peace of God be with you.