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Re: A full spectrum of opinions



>Tom Holtz adds his color commentary (incidentally, Tom, I don't horn
>in on questions about Therizinosauroids... return the favor ;-):

Sorry :-(

>> ...there are several researchers (whose names have all slipped my
>> mind right now) who have shown that sauropsids (birds & reptiles)
>> have four or five different photosensitive pigments.
>
>For a review, see:
>
>Goldsmith, T.H. (1990). "Optimization, Constraint and History in the
>     Evolution of Eyes", _Quart. Rev. of Bio._, 65:281-322.
>
>Perhaps I'm confused, but I thought sauropsid doesn't include anapsid.
>At least some (possibly all... I don't remember) of the turtles
>studied have four visual pigments.  Turtles and birds also share many
>characteristics not found in mammalian retinas, so I suspect that the
>dinosaurs had those features as well.

Sauropsida has basically always been birds plus "reptiles" (including
Anapsida).  Gauthier's current usage of the terms is "Reptilia and all
amniotes sharing a more recent common ancestor with Reptilia than with
Mammalia" - a nonsense group if mammals are closer to diapsids than either
are to anapsids, but a reasonable group if there is an Anapsida+Diapsida
clade exclusive of the synapsids.

                                
Thomas R. Holtz, Jr.                                   
tholtz@geochange.er.usgs.gov
Vertebrate Paleontologist in Exile                  Phone:      703-648-5280
U.S. Geological Survey                                FAX:      703-648-5420
Branch of Paleontology & Stratigraphy
MS 970 National Center
Reston, VA  22092
U.S.A.