Re: feathers, hair and Compsognathus

[Thomas_R_HOLTZ@umail.umd.edu (th81)]

>> It is ABSOLUTELY NOT useful to stick to the Linnean taxonomic rank of
>> "Reptile."  It is Doubly paraphyletic.  It is an awful example of Linnean
>> taxonomy.  Also, birds are defined cladistically as "All the descendants of
>> the most recent common ancestor of both Archaeopteryx and Corvis", and since
>> Sinosauropteryx does not fall within that clade, it is not a bird.
>
>     Not being up on my basal reptile phylogeny, could someone explain
>to me exactly why reptiles are now considered to be a paraphyletic
>group?  I assume this means that thier earliest common ancestor was NOT
>something that shared the traits that has caused scientists to group
>"reptiles" together.  What was this common ancestor, and how was it
>different?

Reptilia is paraphyletic if birds are excluded, since the ancestors of birds
were reptiles.

However, Reptilia is regarded by most systemicists today as a monophyletic
group: all descendants of the most recent common ancestor of turtles,
lepidosaurs, and archosaurs (including birds).

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661

"There are some who call me...  Tim."
-- Tim the Enchanter, "Monty Python and the Holy Grail"
---------- subtitle --[Monty Python ik den Holy Grailen]

"Tim?!?  They called me TIM?!?!"
-- Tom the Paleontologist, on seeing "The Ultimate Guide to T. rex" :-)