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Gauthier, Kluge, and Rowe in "The early
evolution of the amniota within The Phylogeny and Classification of the
Tetrapods, Vol. 1: ampbhians, reptiles, birds, diagnos Reptilia as amoung other
things, having a small supratemporal, a horizontal ventral margin of the
postorbital region in the skull, and fusion between the pluerocenturm of the
atlas and the intercenturm of the axis. Within Amniota, this excludes
Synapsida, and a group they informally refer to as parareptiles, which there
includes, amoung other things, mesosauridae, and procolophonia. Obviously,
this has very little to do with the popoular definition of reptiles, but if one
includes some of these parareptiles, plus the reptilia defined in that paper, in
ones consideration of reptilia, then your reptilia becomes paraphyletic.
Obnes own definition of reptilia could become polyphyletic if they include of of
the parareptiles and the Reptilia in this paper, but not their ancestor.
However its very important to note that the authors of thepaper felt that
parareptiles would turn out to not be a monphyletic group, i beleive this
is based on teh consistancy index of the group being 0.33. So they define
Reptilia as being the last commyn ancestor of anapsida and diapsida, plus all
its descendants, a nodally defined group. parareptiles coul be very close
to reptiles, or they could be very close to synapsids, but it doesn't matter,
because as long as they are between the two they are not part of this node
defined Reptilia.
In the end i suppose, Reptilia has had various
definitions, whereas reptiles are a popular, or "vulgar" term. In my
opinion, this vulgar reptile is something that is recognized upon seeing, not as
someting that fits into a predefined concept. For instance, no one will
consider rats to be reptiles, but if one were to define this vulgar reptile as
being someting posessing scales, then rats with their scaly feet and tail should
be incouded. The echinda would be included if one made it egg laying
animals. I also think most people can understand that birds came from
reptiels, but they wouldn't necessarily consider birds to be reptiles, any more
than they would consider humans to be amphibians because we had an ancestor that
would have been considered an amphibian.
~R.
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