[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

RE: Huge Theropod Database Update

David Howlett wrote-

> Good work :) although I would question your placement of
> Megaraptora within Coelurosauria when as I recall the family
> is accepted to be within the Carcharodontosauridae - in fact
> one member of the family, Neovenator, is still placed here
> by you.

Basically, I have a saurischian supermatrix that includes all the taxa and 
codings from most of the recent large theropod analyses, and I added Benson et 
al.'s (2010) data to it.  And while his data supporting Megaraptora was strong 
enough, his data supporting putting Megaraptora in Carnosauria was not.  
Neovenator still ended up in Carnosauria though, while Chilantaisaurus had a 
less certain placement. In addition to exaniming more characters than Benson's 
analysis, I think one important difference in this case is that he only 
included three coelurosaurs.  Notably, all three (Tanycolagreus, 
Proceratosaurus, Guanlong) are more derived than some other coelurosaurs 
included in my analysis- Gasosaurus and tyrannosauroids.  Which brings us to 
point two...

> I'm also unsure why you have removed a number
> of taxa (including Eotyrannus and the Proceratosauridae)
> from the Tyrannosauroidia when as far as I am aware, they are
> firmly placed within the group.

I do address this in the comments section for each taxon, the most detailed of 
which is for Dilong-
Several cladistic analyses have found this to be a basal tyrannosauroid. Xu et 
al.'s (2004) analysis was a version of Currie et al.'s (2003) cranial-only 
tyrannosaurid analysis, with Dilong and outgroups added. It is not that useful, 
as the characters were designed to distinguish Allosaurus from tyrannosaurids, 
and resolve relationships within Tyrannosauridae, so do not even lead to a 
plausible outgroup topology (e.g. Citipati is the tyrannosauroid sister group). 
Xu et al. (2006) added Dilong and Guanlong to Rauhut's (2003) theropod 
analysis, which was followed by Benson (2008). Both Turner et al. (2007) and 
Senter (2007) added Dilong to the Theropod Working Group's matrix, though the 
latter contained more relevent tyrannosauroid characters. While Senter did find 
it to be a tyrannosauroid, Turner et al. resolved it slightly closer to birds. 
When I add the relevent taxa and all the characters used by Xu et al. (2006, 
2004) to group Dilong with tyrannosauroids to Senter's (2007) matrix, Dilong 
ends up one node closer to birds than to tyrannosaurids (along with apparently 
related taxa Eotyrannus, Coelurus and Tanycolagreus). This is based on numerous 
characters- in lateral view, dorsal border of the antorbital fossa formed by 
the lacrimal and maxilla; round orbit; anterior cervical epipophyses absent or 
poorly developed, not extending past posterior rim of postzygopophyses; 
cervical neural spines dorsoventrally low; short laterotemporal fenestra; 
posterior dorsal neural spines height <1.5× length; humeral length more than 
half femoral length; manual phalanx I-1 longer than metacarpal II; feathers 
present. Constraining Dilong to be a tyrannosauroid results in trees 2 steps 
longer. It's still in the coelurid clade, but the latter is now the basalmost 
clade of tyrannosauroids. At least some of the above characters could be 
size-related, and Senter's matrix certainly has some character correlation 
problems. Two steps isn't very much, so I don't feel a tyrannosauroid identity 
can be ruled out. But at the same ti!
me, it's 
Li et al. (2009) added more relevent characters and taxa to the TWG matrix when 
they described Xiongguanlong.  I've added this data to my modified Senter 
matrix as well, and Proceratosaurus, Eotyrannus, Guanlong, etc. still emerge as 
closer to birds than tyrannosaurids.  However, now we have Sinotyrannus, 
Raptorex, Kileskus and the new data from adding Proceratosaurus and Guanlong to 
Rauhut's matrix (Rauhut et al., 2010) and the data from adding those and 
Kileskus to the Smith et al. matrix (Averianov et al., 2010).  Will they end up 
as tyrannosauroids once I incorporate that data?  It's possible, and if so I'll 
adjust my site accordingly.
Note that in both of these cases though, and as a general site rule, I do 
describe what the current consensus is even if I vary from it.  I want The 
Theropod Database to be the ultimate repository for theropod information, not 
just my platform to air my ideas.
Mickey Mortimer
The Theropod Database- http://home.comcast.net/~eoraptor/Home.html              
The New Busy think 9 to 5 is a cute idea. Combine multiple calendars with