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Re: MR's comment on dino vision



From: "Thomas R. Holtz, Jr." <th81@umail.umd.edu>

 > Extant Phylogenetic Bracket method: ...

Yep.  Hence: dinosaurs had color vision, and probably had a four-
chambered heart, and posessed colorful display structures, and ...

 >  Since living reptiles (including birds) have more
 > sophisticated color vision than mammals, it is more parsimonious to accept
 > that dinosaurs did as well.

The basic evidence is that mammals lost full color vision when they
became nocturnal somewhere around the Late Triassic or Early Jurassic.
Modern mammals with color vision, including humans, have *re-evolved*
it from the remaining pigment variants.

This is based on the molecular phylogeny of the pigment bearing proteins.

This evidence also supports good color vision in dinosaurs, as birds have
retained the reptilian set of pigments, rather than a reconsitituted
set of new pigments like mammals. (In fact I think this virtually proves
good color vision in at least the theropods, and I think the crests
and frills tend to suggest color vision in ornithischians as well).


swf@elsegundoca.ncr.com         sarima@ix.netcom.com

The peace of God be with you.