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Re: Archosaur Origins...was:MESENOSAURUS ERRATA.
<< 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. >>
Amen and halleluiah, George. Though you and I sometimes disagree about the
definition of BCF (birds-came-first, brooding-came-first) I am solidly behind
you on this one. It is too easy to insist that the most ancient creatures
were primitive and must have had certain expected physical traits. But the
fossil record should not be over-interprted -- in either direction -- being
that it is so full of holes. Who ordains SCF (scales-came-first)? No one,
I am very lonesome in a viewpoint I hold: integumentary appendicular
structures are extrememly ancient, and ALL are derived from a common ancestor
(parsimoniously speaking). There IS evidence for this view, in that the WNT
gene locus seems common to all such structures, from feathers to teeth.
Consider the shark. It has a pelage of sorts all over its body -- one that
erupts from follicles and sticks out -- teeth (or dermal denticles). Now
then, when did sharks evolve?
If anybody on the planet wants to join me on this one, we might be able to
agree that a molecular fossil exists in the genome: WNT. Thus, pelage could
easily have existed in the Devonian, depending on what limits we place on
what we call pelage. I'm satisfied that there is evidence of an extrememly
ancient structure, call it what you will, that erupted from follicles on the
skin. Scales are just one form of this, nothing special though notable for
So you see, we ought to think TCF (teeth-came-first) probably among some
annelids in the Precambrian, and all other surface coverings of pointy long
things evolved from there. Timing? Which came second? Which came third? Hmmm.
Now, if I'll allow that the theropod Oviraptor might -- just might -- have
had a birdy ancestor, will you allow that maybe -- just maybe -- Microraptor
covered its babies with those long feathers on its ulnae?
Thomas P. Hopp
Author of DINOSAUR WARS, a science fiction novel published by iUniverse
Now Humans are the Endangered Species! http://members.aol.com/dinosaurwars