RE: Sereno's (2005) new definitions

[Michael Mortimer <mickey_mortimer111@msn.com>]

Tim Williams wrote-

> > Neotetanurae
> > (Sinraptor dongi + Carcharodontosaurus saharicus + Allosaurus fragilis + 
> > Passer domesticus)
> > This differs from the original definition (Sereno, 1998) by adding 
> > Sinraptor and Carcharodontosaurus as internal specifiers.  I suppose it 
> > would preserve content better if sinraptorids or carcharodontosaurids end 
> > up just basal to carnosaurs + coelurosaurs (Paul, 1988; Coria and Salgado, 
> > 1995; Longrich, 2001; Paul, 2002).  However, if carcharodontosaurids are 
> > ceratosaurs (Bonaparte et al., 1990) or sinraptorids are megalosauroids 
> > (Kurzanov, 1989), the original intent of Neotetanurae would be lost.
>
> Not only that, but given that Tetanurae is now re-defined to exclude 
> _Ceratosaurus_ and _Carnotaurus_, having carcharodontosaurids as 
> ceratosaurs would produce a Neotetanurae that is *more* inclusive than 
> Tetanurae.  Thus, Tetanurae would be a clade within Neotetanurae.  Ass 
> backwards, to say the least.

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

> > Coelurosauria
> > (Passer domesticus <- Allosaurus fragilis, Sinraptor dongi, 
> > Carcharodontosaurus saharicus)
> > One thing I object to is the use of Passer as an internal specifier for 
> > Coelurosauria, as birds were not originally classified as coelurosaurs in 
> > Huene, 1914 or by anyone until the 1970's at least. Huene included what 
> > would today be called coelophysids, coelurids, compsognathids, 
> > Ornitholestes and ornithomimids.  The best internal specifier for 
> > Coelurosauria in my opinion is Ornithomimus.  It's always been a 
> > coelurosaur,
>
> I had thought Ornithomimosauria was originally erected (by Barsbold, 1976) 
> to be a separate group from Coelurosauria.  Thus, _Ornithomimus_ would not 
> have been a coelurosaur when Ornithomimosauria was proposed.  Why not use 
> the eponymous genus _Coelurus_ as the internal specifier for Coelurosauria? 
>  Surely _Coelurus_ has always been considered a coelurosaur... hasn't it?

Good point about Barsbold's scheme, where Coelurosauria was reduced to a 
paraphyletic group.  Interestingly, although Barsbold viewed oviraptorosaurs 
and deinonychosaurs as being coelurosaur derivatives, he thought 
ornithomimosaurs were probably more closely related to carnosaurs.
I'm not sure Coelurus is eponymous with Coelurosauria.  It was positioned 
further from Passer than Allosaurus by Paul (1988), but so were all of 
Barsbold's coelurosaurs.  My main concern with Coelurus is that only this 
year has it finally been described well enough to be evaluated, and previous 
analyses (biased as they were by including Tanycolagreus manual info) tend 
to place it VERY basally within the Coelurosauria.  Makovicky (1995) had it 
as the most basal, as does my analysis most of the time. Rauhut's (2003) had 
it as the most basal except for Proceratosaurus.  Holtz (2000) had it the 
most basal except for Ornitholestes, Proceratosaurus, Dryptosaurus and 
Gasosaurus.  I suppose I'm backing Sereno's 'well-nested' philosophy here.
A third possibility is Compsognathus, which has been known from a complete 
skeleton for a long time, and has been placed with coelurosaurs by everyone 
except Paul (1988) and Novas (1992).  It's also been analyzed far more often 
than Coelurus, but is similarly not well nested in some phylogenies (Holtz, 
1994; Holtz et al., 2004).  Still, after examining Holtz's characters, I 
find placing it that basal to be very poorly supported.

> > Therizinosauria
> > (Therizinosaurus cheloniformis <- Tyrannosaurus rex, Ornithomimus 
> > edmontonicus, Shuvuuia deserti, Oviraptor philoceratops, Troodon formosus)
> [snip]
> > If anything, I might suggest using Plateosaurus and Stegosaurus as 
> > additional specifiers instead, just to ensure views like Paul's (1984, 
> > 1988), Sereno's (1992) and Olshevsky's are covered.
>
> Paul's and Sereno's papers are quite old, and written before the discovery 
> of _Beipiaosaurus_, which seems to cement the therizinosaurs among the 
> higher theropods.  I think the therizinosaurs-as-sauropodomorphs or 
> therizinosaurs-as-basal-phytodinosaurs classifications are of little more 
> than historical interest.  Olshevsky's current views are unpublished, 
> AFAIK, but any definition probably should not have to accommodate his 
> revolutionary ideas on dinosaur evolution.  This is not a criticism of 
> George Olshevsky - but his "Birds-Came-First" theory is so heterodox that 
> it would stretch *any* phylogenetic definition to breaking point.

That's quite true, but at least the topologies have been suggested, unlike 
therizinosaurs-sister-to-tyrannosauroids.  Still, I agree the use of 
sauropodomorphs or ornithischians as external specifiers is fairly 
uneccessary.
In regards to BCF, the phylogeny is actually fairly standard, it's just the 
sequence of character transformations that aren't.  So only apomorphy-based 
definitions like Gauthier et al.'s Avialae, Avifilopluma, Aviremigia and 
such would be affected.

> > Troodontidae
> > (Troodon formosus <- Ornithomimus edmontonicus, Velociraptor mongoliensis, 
> > Passer domesticus)
>
> One fly in the ointment.... _Troodon formosus_ may one day be declared a 
> nomen dubium, given that it has isolated teeth as its type material.  Maybe 
> _Stenonychosaurus_ or _Saurornithoides_ should be used as an internal 
> specifier instead of _Troodon_.  Come to think of it, perhaps the family 
> Troodontidae should be replaced by Saurornithoididae, and ICZN rules on 
> priority be damned!  :-)  Hey, Parvicursoridae was trumped by the later 
> Mononykidae, so why not replace Troodontidae with Saurornithoididae?

But Troodon seems to be a very close relative of the Saurornithoides 
holotype regardless of its validity, so I don't think this matters.  I'm not 
happy about Mononykinae winning over Parvicursorinae, personally.  
Parvicursor isn't even very poorly known or potentially invalid.

> The only potential problem with Sereno's definition of Deinonychosauria is 
> that what happens if _Microraptor_ is basal to the 
> Troodontidae+Dromaeosauridae clade?  With a node-based clade anchored in 
> _Troodon_ and _Velociraptor_, microraptorans would no longer be 
> deinonychosaurs.  This is not a deal-breaker, but it does go against the 
> grain of the traditional usage of Deinonychosauria.  Maybe _Microraptor_ 
> should be added as a third internal specifier.

I'd agree, if using the node-based definition.

> One potential pitfall to the above stem-based definition is in the event 
> that we get a topology that shows a clade that includes _Archaeopteryx_ and 
> _Confuciusornis_, but not _Passer_ (or even enantiornithines).  In other 
> words, a rump Sauriurae.  Should this happen, Confuciusornithidae (or 
> -iformes) would engulf _Archaeopteryx_ as well.  Given just how 'froggy' 
> basal avian phylogeny is, I think definitions pertaining to this part of 
> the tree should have many external specifiers.  I would use both 
> _Archaeopteryx_ and _Enantiornis_ as external specifiers for a stem-based 
> Confuciusornithidae (or -iformes).

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.

> I would have used (Archaeopteryx lithographica <- Passer domesticus) to 
> define Archaeopterygiformes, and have a narrower definition of 
> Archaeopterygidae.  Again, just personal preference.

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.

> Did Sereno name and define a Paraves+Oviraptoriformes clade?  In other 
> words, a clade of maniraptorans that is limied to therizinosaurs, 
> oviraptorosaurs, deinonychosaurs, and birds?

No.  The only taxon that might fit is Chuniaoae from Ji et al. (1998).  It 
was intended as a term for the Caudipteryx + Passer clade in their analysis, 
but was deleted from the paper except for the supplementary information.  Of 
course, it wasn't formally defined.  Plus it excluded dromaeosaurids, so is 
similar to Metornithes in that regard.
Don't confuse it with Chuniaoia from Ji and Ji (2001), which was a name 
applied to a stem leading to Protarchaeopteryx on a cladogram.

Mickey Mortimer