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Re: Ichthyornis paper



I wrote-

> So, we have our first phylogenetic definitions for a Mesozoic dinosaur
genus
> and species.  What does everyone think?

Oops.  Sereno (1998) defined Stegoceras (Stegoceras validus <-
Pachycephalosaurus) and Archaeopteryx (Archaeopteryx lithographica <-
Neornithes).  But Clarke still has the first species definitions and the
first _good_ genus definition.  I'm actually fond of her method of defining
Ichthyornis, despite my usual hatred for apomorphy-based definitions.  By
citing several apomorphies that must be present, the original concept is
retained, and Ichthyornis works just as well as a member of a speciose side
clade as it would if the only ichthyornithine were I. dispar.  Contrast with
Sereno's definition of Archaeopteryx, which could include all dromaeosaurs
in some phylogenies, and effectively stops any further archaeopterygids from
being named.  Her Guildavis, Iaceornis, Apatornis and Austinornis
definitions, unfortunately, face a less extreme but analogous problem to
Sereno's.

Also interesting from Clarke's paper is her dismissal of Dyke et al.'s
(2002) bird from the Maastrichtian Netherlands as Avialae incertae sedis,
and for good reasons.  Seems it doesn't resemble Ichthyornis much after all.

Mickey Mortimer
Undergraduate, Earth and Space Sciences
University of Washington
The Theropod Database - http://students.washington.edu/eoraptor/Home.html