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Re: Arctometatarsalia



Ken Kinman (kinman@hotmail.com) wrote:

<I just read Brian's (philidor's) post, and I think people should simply
stop using the taxon name Arctometatarsalia, along with a few other names
(like Carnosauria).  Almost all groups with arctometatarsalian feet
(arctomets, subarctomets, hyperarctomets) are not members of
Arctometatarsalia, and that seems rather senseless.  It would be like
keeping "Vermes" around for just the earthworms (if someone had anchored
Vermes on an earthworm genus).>

  Typically, an arctometatarsalian pes has an exact quality of definition
that does not include the quality of the subarctomet pes (as in
dromaeosaurs and oviraptorids). The hyperarctomet pes still meets all the
criteria of the arctomet definition of Holtz, 1994, and thus can be as
such made a sub-type. But the "true" arctomet condition is, btw, shared
only by a few taxa as is based on a functional feature. This does not
devalue the taxon based to include it as it's content was originally
defined by inclusion of *Ornithomimus*, but not birds. This makes
Arctometatarsalia the stem opposing Maniraptora.

  Now recently, a lot of people have tried to say that a name that
includes an apomorphy in it's etymology should, reasonably, include that
apomorphy as part of its definition, or _as_ it's definition. Hence,
Gauthier and de Quieroz (2001) revise a decade of use of Carinatae
{*Ichthyornis* + Neornithes} to turn it into a clade that is, effectively,
a senior synonym of Ornithodira by defining the taxon on a carinate keeled
sternum, and define that in such a manner that one can make pterosaurs fit
it without stretching the imagination. Thus, they destroy a taxon's
usefulness and application as a bird group to include all of Archosauria,
among other things. Thus only reinforces the problematic usage of
apomorphy-based taxa and reasoning (a name that sounds like a feature
should be defined on this feature). I would refuse to use Gauthier and de
Queiroz' definition on the sole grounds of _their_ application of priority
of definition (1992) being tied to Carinatae {*Ichthyornis* + Neornithes};
hence, by application, Arctometatarsalia {*Ornithomimus* > Neornithes},
not Arctometatarsalia {arctometatarsus in *Ornithomimus* where an
arctometatarsus is thus...}.

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

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