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RE: New gliding reptile: Mecistotrachelos

Paula Goodman wrote:

*how do the wings of this new fossil relate to the maybe-feathers/maybe-scales wings of the Longisquama?

In their description of _Mecistotrachelos_ Fraser &c leave open the question of where exactly _Mecistotrachelos_ might lie in diapsid phylogeny, though they tentatively suggest it is an archosauromorph (i.e., closer to birds and crocodiles than to lizards and snakes). It might even be closely related to _Sharovipteryx_

The kuehneosaurs, another group of extinct gliding diapids, are usually regarded as lepidosauromorphs (i.e., closer to lizards and snakes than to birds or crocodiles).

_Longisquama_ isn't mentioned in the description, but an analysis of _Longisquama_ a few years back (Senter, 2004) recovered _Longisquama_ in a group he called the Avicephala, which also includes drepanosaurids and coelurosauravids. This group lies somewhere near the base of the Diapsida, outside both the archosauromorphs and lepidosauromorphs.

So to answer your question, at the moment there does not appear to be any unique connection between _Mecistotrachelos_ and _Longisquama_. Gliding abilities appear to have evolved several times independently among small diapids. Having said that, the precise function and arrangement of the dorsal structures of _Longisquama_ is not known; it could be a single file, or a paired structure like _Coelurosauravus_ or _Mecistotrachelos_ or keuhneosaurs.

Nor does there appear to be any connection at all between _Longisquama_ and birds; the dorsal structures present in _Longisquama_ (which *might* have been used for gliding) do not appear to be homologous to bird/theropod feathers. _Longisquama_ is only distantly related to birds; if Senter's analysis is correct, _Longisquama_ is no more closely related to birds than to lizards or snakes.



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