Arctometatarsalia and Alvarezsauria

["Jaime A. Headden" <qilongia@yahoo.com>]

Okay, Class, for those not listening

  one ...

  more ...

  time ...

  Arctometatarsalia does not refer to a mono- or holophyletic groups of
_anything_. It is a group _defined_ on the condition of relatedness
compared to *Ornithomimus* and birds. If it's closer to the former than to
the latter, then it is an arctometatarsalian, a member of the taxon
Arctometatarsalia. It lacks rank, it is rankless inclusive taxon that, as
of the Xu et al study (you know, the *Sinovenator* one) that finds
Tyrannosaurids on one side (more basal) and troodontids next to birds,
includes _only_ Ornithomimosauria (defined on the inclusion of
*Pelecanimimus* and *Ornithomimus*, the one taxon from which they had a
common descent, and any descendant of that taxon, which just happens to
include *Pelecanimimus* and *Ornithomimus*). When Barsbold, in 1976, first
described this group, and in his subsequent publications (inluding the
1977, 1981, 1983, and 1988 papers) he used the rank Infraorder to define
this. Barsbold Rinchen no longer ranks his taxa.

  As for Alvarezsauria, this name was coined in Bonaparte's inimitable
excessive monotypic style, and it was originally described to include
_only_ Alvarezsauridae, and in that, _only_ *Alvarezsaurus*, which
included _only_ *Alvarezsaurus calvoi*.... No one named it to include
anything other than that taxon. I have no idea where that misinformation
started. Perle, Clark, and Norell, in 1993, described the taxon
*Mononykus* _after_ Bonaparte described *Alvarezsaurus* (1993 compared to
1991), incidentally creating the monotypic Mononykidae in the process, and
it wasn't until 1996 with the analysis of Novas and that of Chiappe,
Norell, and Clark (both 1996 in the _Memoirs of the Queensland Museum_
dino volume (also describing *Patagonykus* for the first time, prior to
Novas' JVP paper on the taxon in 1997)) that *Alvarezsaurus* and
*Mononykus* (along with *Patagonykus*) were first allied. Karhu and
Rautian (an ornithologist and paleontologist) described the diminutive
*Parvicursor* in roughly the same time, and _also_ created a monotypic
taxon to enclose it, Parvicursoridae. They provided affinities to
Mononykidae, but did not synonymize the two. ... [big breath] ... This led
to 1998 with Clark, Norell, and Chiappe describing the most recent taxon,
*Shuvuuia*, which was immediately referred to the Mononykidae, along with
*Parvicursor*, dismissing the Parvicursoridae and subjectively synonymous
with Alvarezsauridae, along with Mononykidae, and provided that all five
genera were alvarezsaurids. At this point, Alvarezsauria is still
monotypically inclusive of one "family" and two junior synonyms.
Non-*Alvarezsaurus* and *Patagonykus* alvarezsaurids are now called
Mononykinae, though I beleive this name has not actually been coined in
the literature.

  *Parvicursor* lacks any features to suggest it is intermediate between
*Patagonykus* and *Mononykus* or *Shuvuuia* (Chiappe et al., 1998;
Chiappe, 1997) and it is therefore most reasonable to state that they form
a monophyletic trinity with *Patagonykus* outside of it. Therefore, a
separate Parvicursoridae is ridiculous and excessive and does not qualify
differentiation.

  With one or two other mononykes hanging around, this group is filling
out, and Novas suggested that a partial vertebrae may represent a coeval
species of alvarezsaur in his description of *Patagonykus* (in both 1996
and 1997 papers). And this is where the systematics stand presently.

  Alvarezsauria Bonaparte, 1991
    Alvarezsauridae Bonaparte, 1991
      Alvarezsaurus Bonaparte, 1991
      Patagonykus Novas, 1996
      Mononykinae (modified from Perle et al., 1993)
        Shuvuuia Chiappe et al., 1998
        Mononykus Perle et al., 1993
        Parvicursor Karhu and Rautian, 1996
        NA mononyke (Hutchinson and Chiappe, 1999)

  [once again, let's not mention the _other_ ones, you know what I'm
talking about.... :) ]

=====
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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