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Mesozoic birds (was Re: Different twist of BCF)



At 05:25 PM 12/2/96 -0500, Caitlin Kiernan wrote:

>Ronald Orenstein wrote:
>
>> Unless I am much mistaken, birds like Sinornis or even Hesperornis
>> are not considered to be enantiornithine.
>
>-Hesperornis- and -Ichthyornis- are traditionally grouped together in the
>superorder Odontognathae (within the orders Hesperornithiformes and
>Ichthyornithiformes, respectively),

Actually, Odontornithes is the traditional form.  However, this is probably
an unnatural grouping, as all recent studies have shown.
Ichthyornithiformes, Hesperornithiformes, and Neornithes are all very
closely related to each other, but the exact topology is still being worked
out.  Some place Hesperornis and its relatives closer to neornithines,
others place Ichthyornis and kin closer to neornithines.

>and I'm under the impression that the Enantiornithiformes has
>ordinal rank, though its relationship to the odontognathids is
>unclear. Has this changed?

Well, the rank is pretty much unimportant in most studies.  However,
Enantiornithiformes is a very diverse group, containing such forms as
Sinornis, Cathayornis, several of the Las Hoyas birds, etc.  They are less
closely related to neornithines than are Patagopteryx, Hesperornis,
Ichthyornis, etc.

Feduccia, Martin, and others "Saururae" (not to be confused with the old
version, the subclass of birds containing only Archaeotperyx), a group they
suggest containing Enantiornithiformes, Confuciusornis, Archaeopteryx, etc.,
is almost certainly paraphyletic, is based on some very questionable
character polarities (to put it kindly...), and requires massive
convergances between enantiornithines and ornithurines (neornithines,
hesperornithiforms, ichthyornithiforms, etc.)

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

"To trace that life in its manifold changes through past ages to the present
is a ... difficult task, but one from which modern science does not shrink.
In this wide field, every earnest effort will meet with some degree of
success; every year will add new and important facts; and every generation
will bring to light some law, in accordance with which ancient life has been
changed into life as we see it around us to-day."
        --O.C. Marsh, Vice Presidential Address, AAAS, August 30, 1877