RE: Sereno's (2005) new definitions

[Tim Williams <twilliams_alpha@hotmail.com>]

Mickey Mortimer wrote:

> Good point.  So maybe (Sinraptor dongi + Allosaurus fragilis + Passer 
> domesticus) ?

That seems a nice definition for Tetanurae.

> I'm not sure Coelurus is eponymous with Coelurosauria.

I'm not sure either.  In any case, it would be strange to have a 
Coelurosauria without _Coelurus_.  In lieu of the fact that _Coelurus_ is 
quite poorly known, maybe _Ornitholestes_ could be used as an internal 
specifier.  However, _Ornitholestes_ could turn out to be closer to 
_Allosaurus_ than to traditional coelurosaurs (e.g., Paul [1988]).  As 
Mickey suggested, _Compsognathus_ could also be used; but compsognathids do 
jump around the tree a bit.  The problem is that basal coelurosaur phylogeny 
is a little wobbly, so it's difficult to pin down a taxon that is 
well-nested.

I can see the logic behind Sereno's definition of Coelurosauria: (Passer 
domesticus <- Allosaurus fragilis, Sinraptor dongi, Carcharodontosaurus 
saharicus).  Instability at the base of the Coelurosauria does not pose a 
problem under this definition, and the Coelurosauria will always be assured 
of excluding 'traditional' carnosaurs like _Allosaurus_.

> In regards to BCF, the phylogeny is actually fairly standard, it's just the 
> sequence of character transformations that aren't.

Given that a phylogeny is a *product* of character transformations, this 
approach is incongruous to say the least.  BCF keeps the topology, but 
re-writes the characters that were used to generate the phylogeny.  BCF also 
alters the 'standard' phylogeny at the base of the Dinosauria: BCF gives 
sauropods as basal dinosaurs; lagosuchians as basal theropods; and 
sauropodomorphs closer to ornithischians than to theropods.  This last one 
(i.e., a monophyletic Phytodinosauria) is feasible, though not 
well-supported at the moment.

However, the fact remains that the BCF "phylogeny" is not actually generated 
using cladistic methodology.  The same applies to Martin's "Sauriurae" and 
Gardiner's "Haematothermia" and (going back even further) Cuvier's 
"Pachydermata".  I wonder if we should even bother trying to erect 
definitions that can accommodate extremely heterodox or discredited 
groupings.

> But Troodon seems to be a very close relative of the Saurornithoides 
> holotype regardless of its validity, so I don't think this matters.

So clades can be anchored using nomina dubia?  _Troodon_ is not a nomen 
dubium, but if more troodontid material is unearthed that shows more than 
one troodontid species existed in Campanian-Maastrichtian North America, and 
they all had the same dental morphology, then _Troodon_ is toast.  _Troodon_ 
will go the way of _Deinodon_ and _Trachodon_ (unless the ICZN approves a 
neotype).

> Well, if we have this situation, then the older Archaeopterygidae/iformes 
> would be a senior synonym, right?  I agree it sounds best to keep 
> Confuciusornis out of Archaeopterygidae, but having it in 
> Archaeopterygiformes sounds reasonable given this hypothetical topology.

Yes - in the unlikely event that this should happen, it would be better to 
have _Confuciusornis_ in Archaeopterygidae/iformes than have _Archaeopteryx_ 
in Confuciusornithidae/iformes

> Under some plausible topologies, this could include dromaeosaurids and 
> troodontids in Archaeopterygiformes.  I think Paul (1988) did the former, 
> but I'm not sure how well accepted it would be.

Should these topologies arise, I think it would be entirely appropriate that 
deinonychosaurs be put inside the Archaeopterygiformes.  After all, these 
topologies would indicate that _Archaeopteryx_ shares a common ancestor with 
deinonychosaurs to the exclusion of modern birds.

> No.  The only taxon that might fit is Chuniaoae from Ji et al. (1998).

What do "Chuniaoae" and "Chuniaoia" actually mean?

Cheers

Tim