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Theropod polyphyly vs BCF



George wrote:

I think what he is arguing is that the theropod bauplan evolved several times
independently in nondinosaurian archosaurs, and that we're lumping all these
lineages into Theropoda because of their homoplasies. This isn't BCF, since
BCF assumes dinosaurian and theropod monophyly.


My response was somewhat tongue-in-cheek. Yep, what he is saying that the bird-like theropods are more closely related to _Longisquama_ than to other theropods, and most of the similarities are due to convergent evolution between two independent lineages. The former lineage was favored to survive into the Cretaceous as a result of some end-of -Jurassic "minor holocaust" (an oxymoron?). The "dogma", of course, is that the Theropoda is monophyletic.

The similarity to BCF is that an arboreal _Longisquama_-like ancestor gave rise to ground-dwelling bird-like theropods.

Personally, I'm ready to believe that many Cretaceous maniraptorans may have evolved from a volant pre-archaepterygid theropod (which would explain the feathers in _Caudipteryx_ -it's secondarily flightless). But the fossils we currently have available don't support that hypothesis.


Tim

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