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Re: Theropod phylogenies




"Richard Forrest" <richard@plesiosaur.com> wrote:


If phylogenies based on the morphological analysis of the skeletons of
modern birds are so unreliable, surely the same must be true of cladistic analyses of theropod dinosaurs,

A quick answer...

I would disagree. The biggest obstacle to resolving the interrelationships of modern birds is their fossil record: It's utterly dreadful. This is especially the case when it comes to the basal representatives of modern avian orders.

especially if they are so closely related to
modern birds that some contributors to this site make no distinction?

Many folks (myself included) are convinced that birds are a subset of theropod dinosaurs. Nevertheless, we still make a distinction between birds and non-avian theropods. Similarly, the contention that bats are flying mammals still allows us to delineate between bats and non-chiropteran mammals.


And if this is the case, don't we need to treat these cladograms as rather tentative hypotheses rather than solid phylogenies?

Unless the Almighty tells us how individual lineages evolved, we are never going to KNOW what happened. Whatever your method of choice is for resolving relationships - fossil data, molecular data, pure intuition, or combination of these - you can never be certain of how evolution occurred. All we can do is see how each hypothesis stacks up against the available evidence. In this respect, I think the birds-are-dinosaurs hypothesis is looking pretty darned good.




Tim

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