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Re: Archosaur Origins...was:MESENOSAURUS ERRATA.



On Sat, 25 Aug 2001 Dinogeorge@aol.com wrote:

> With regard to integument, I was referring to that of possible >arboreal
> prolacertiforms<. If pterosaurs are prolacertiform descendants, then it is
> quite possible that some prolacertiforms already had the kind of hairlike
> "pelage" that is well known in pterosaurs.

IIRC, there are possible hairlike structures in _Cosesaurus_.

> This may, in turn, have also appeared other prolaceriforms, such as
> those from which those animals widely known as archosaurs evolved,

Are you using Prolacertiformes as a doubly paraphyletic group of
non-pterosaurian, non-archosauriform archosauromorphs?

Has it ever been defined as a clade? Clade(_Prolacerta_ <-- _Passer_,
_Crocodylus_) might work well, although then it could be synonymous with
_Pterosauromorpha_.

> and it may have been preserved in the arboreal
> lineages that led to birds and dinosaurs. Secondary loss of hairlike
> "pelage," or conversion to smooth scutes, might be expected in aquatic
> reptiles such as proterosuchians, so absence of hairlike "pelage" in these
> groups does not preclude its existence in ancestral prolacertiforms.

Interesting, although that doesn't explain the lack of hairlike pelage in
terrestrial forms such as ceratopsids, hadrosaurids, titanosaurs, and
carnotaurines.

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