RE: aviformes

["Tim Williams" <twilliams_alpha@hotmail.com>]

Tom Holtz wrote:

> We need the context for this.  "Aviform" means "bird shape".  Might you be
> referring to Alan Feduccia's "avimorph thecodonts": his para-/polyphyletic
> assemblage of diapsids including drepanosaurids like Megalancosaurus and
> other taxa like Longisquama which he postulates were the arboreal ancestors
> of birds?


And don't forget _Scleromochlus_, the third member of Feduccia's trinity of 
"avimorph thecodonts".  You see, _Scleromochlus_ has long arms like a 
bird...

The reason why the term "avimorph thecodonts" is so nebulous and 
taxonomically meaningless is eloquently mentioned by Kevin Padian:

http://www.sigmaxi.org/amsci/bookshelf/Leads97/Feduccia97-03.html

(Though I think _Megalancosaurus_ is best interpreted as arboreal rather 
than aquatic.  Either way, its skeleton is manifestly unsuitable for it to 
be considered a likely proavian.)


Reference:

Feduccia, A and Wild, R. (1993).  Birdlike characters in the Triassic
archosaur _Megalancosaurus_.  Naturwissenschaften 80 (12): 564-566.


Tim


---------------------------------------------------------------------

Timothy J. Williams

USDA-ARS Researcher
Agronomy Hall
Iowa State University
Ames IA 50014

Phone: 515 294 9233
Fax:   515 294 3163



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