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



Dinogeorge@aol.com wrote:

<< 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, 
hopefully.
   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 
their flatness.
  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