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Re: Pterodactyloids may not have been monophyletic



>
>Group one, consisting of sharp-snouted "rhamphorhynchoids" (_Rhamphorhynchus,
>Campylognathoides_) and sharp-snouted "pterodactyloids"  (_Nyctosaurus,
>Pteranodon, Germanodactylus, Tapejara, Anhanguera, Tupuxara, Dsungaripterus_)
>also have proportionately longer wings, a longer tail, a shorter neck, and
>were apparently fish-eaters who caught their prey by stabbing it while
>flying.
>
>Group two, consisting of round-snouted "rhamphorhyncoids" (_Dorygnathus,
>Angustinaripterus_) and round-snouted "pterodactyloids" (_Pterodactylus,
>Ctenochasma, Gallodactylus, Gnathosaurus, Pterodaustro, and Huanhepterus_)
>also have proportionately shorter wings, a shorter tail and many were filter
>feeders.  The "rhamphorhynchoids" in this group seem to have basket caught
>fish while wading, perhaps a way-station toward filter-feeding.
> _Huanhepterus_ with its super-long neck and long beak could be ancestral to
>azdarchids, so _Zhejiangopterus and Quetzalcoatlus_  also belong to group
>two.  In these forms, apparently the filter teeth disappeared and an
>edentulous beak, convergent with group one, appears.  Either that or they are
>direct descendents of _Pterodactylus antiquus_, which seems more likely.
>

Obviously the only way to determine if your Group one and Group two
assemblages are each monophyletic (to the extent that you can do it at all)
is by further and more detailed examination of the specimens.  But your
description sounds very much like the description, not of phylogenetic
assemblages, but of adaptive suites, and therefore likely to represent
convergences.  This is akin to the view that all foot-propelled diving birds
(eg loons, grebes, hesperornithids) are related because of structures that
are clearly adaptations to that particular mode of life.

A priori I would be more impressed by common characters shared by forms that
clearly had very different adaptive suites, as these would in my view have a
better chance of representing true synapomorphies than characters whose
state might be driven by similar modes of life.
--
Ronald I. Orenstein                           Phone: (905) 820-7886 (home)
International Wildlife Coalition              Fax/Modem: (905) 569-0116 (home)
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