RE: Microraptor and Birds

["Tim Williams" <twilliams_alpha@hotmail.com>]

T. Michael Keesey wrote:

> You seriously wouldn't mind sparrows, eagles, ostriches, penguins, etc. 
> being
> archaeopterygiforms?

Not at all.  In the context of the entire Theropoda, sparrows, eagles, 
ostriches, penguins etc (and dromies and troodontids too) are the most 
"_Archaeopteryx_-like" after all.

> Personally, I think Archaeopterygiformes would be better for 
> Clade(_Archaeopteryx lithographica_ <- [insert favorite neornithean species 
> here]), especially since your suggested Archaeopterygiformes is a
> heterodefinitional synonym of _Paraves_.

True, Archaeopterygiformes under my definition (all maniraptorans closer to 
_Archaeopteryx_ than to _Oviraptor_)  would be effectively equivalent to 
Sereno's (1998) definition of Paraves (all maniraptorans closer to 
Neornithes than to _Oviraptor_).  This is because most recent analyses 
generate a _Archaeopteryx_+Neornithes clade that excludes oviraptorids.  My 
Archaeopterygiformes is a junior synonym of Paraves as long as maniraptoran 
phylogeny remains stable in this respect.

However, what happens if in future analyses oviraptorids come out closer to 
Neornithes than _Archaeopteryx_ is?  In other words, what if oviraptorids 
and Neornithes form a clade to the exclusion of _Archaeopteryx_, as some 
folks already advocate.  Hey, it could happen.  Thus, Archaeopterygiformes 
would include _Archaeopteryx_ (by definition) and its nearest relatives 
(probably deinonychosaurs); Caenagnathiformes would include oviraptorosaurs 
and modern birds.

> (Caenagnathiformes, though -- that could work....)

Under current phylogenies, this would be the 
Oviraptorosauria+Therizinosauroidea clade which, as Darren pointed out, is 
in desperate need of a name.  It is guaranteed to include _Caenagnathus_ 
(=_Chirostenotes_), especially if _Caenagnathus_ is substituted for 
_Oviraptor_ in the above definition.

> If they lack it because it's secondarily lost, I don't think this is a big 
> deal
> (unless perhaps, the majority of members have lost it).

I don't think this is a problem; after all, none of the over 10,000 species 
of modern birds have a raptorial manus.  I do agree with you that secondary 
loss of an apomorphy is no big deal, and should not invalidate a name.  On 
that point, I would mention that _Ornitholestes_ is considered the most 
basal maniraptoran in recent phylogenies, and its manus is unknown.  Ditto 
for _Deltadromeus_ and _Proceratosaurus_, two taxa that are sometimes 
considered closest to _Ornitholestes_.

> And of course, there are some problems with apomorphy-based taxa -- such as 
> questions
> like, "At what point is a pes truly 'arctometatarsalian'?")

Exactly right.  And on the same theme, at what point does a feathered wing 
become a flight-generating wing?

> "Enigmoraptora", "Enigmodracones" (sp?), "Aenigmosauria", etc. don't refer 
> to a dubious genus (or any genus), and don't refer to any character -- they 
> are suitable for any node- or stem-based definition.

One solution is to name new clades after their respective anchor taxa.  For 
example, Tyrannoraptora would include all descendents of the most recent 
common ancestor of _Tyrannosaurus_ and _Velociraptor_.  This wasn't the way 
Sereno defined Tyrannoraptora, but it retains the same membership.  
Similarly, coining Ceratocarna (or Ceratotaura) for the 
_Ceratosaurus_+_Carnotaurus_ clade would avoid clumsy terms like 
Neoceratosauria or Ceratosauroidea, and is founded on two of the best known 
genera.   The Oviraptorosauria + Therizinosauroidea clade could become 
Segnochira, after _Chirostenotes_ and _Segnosaurus_, which would become new 
anchor taxa.

OK, this is all a little tongue-in-cheek.  What I'm trying to get at is that 
it would be nice to find a naming convention that avoids the contentiousness 
that can arise from either apomorphy-based or genus-based clade names.



Tim

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