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Re: feather tracts (and protoscutes)




Mike, YES!!! In the Triassic there were probably many different structures that were intermediate between feathers and scutes. Longisquama is "hard evidence" of such structures in my opinion. Such structures probably evolved many different times among archosauromorphs, so calling those of Longisquama by the term "feathers" could be very misleading. But on the other saying that they have nothing to do with feathers at all is also somewhat misleading. The truth is probably somewhere in between. In any case, the protofeathers (which I proposed started on the tail and went up the back) could perhaps equally well be termed "protoscutes". That is why I am trying to get Jaime and others to speculate more and resist the urge to extrapolate too heavily from Cretaceous forms back to their Triassic ancestors. This seems to be why the whole BCF movement is increasingly catching on. ----- Cheers, Ken P.S. So now maybe you can better understand when some of us look suspiciously up the assumption that Thyreophora is holophyletic. ******************************************************

From: "T. Mike Keesey" <tmk@dinosauricon.com>
Reply-To: tmk@dinosauricon.com
To: -Dinosaur Mailing List- <dinosaur@usc.edu>
Subject: Re: feather tracts
Date: Mon, 16 Jul 2001 13:05:17 -0400 (EDT)

While working on a new 3D abelisaur, It occurred to me that the large
semiconical scutes of _Carnotaurus_ (which I used as a basis) pretty much
occur in "tracts". Large crocodylian scutes also occur in definite rows;
in fact when they project along the edge of the forelimb they can be
rather reminiscent of bird wings. Could there be a homologous relationship
between the patterns of large scutes in non-avian archosaurs and the
feather tracts of avians?

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