Re: Therizinosauroids and the Question of the "Segnosaur" Pelvis [long!]

[Dinogeorge@aol.com]

In a message dated 2/3/99 1:53:01 AM EST, qilongia@yahoo.com writes:

<< 
   I can't wait to get my hands on the rest of this data, that of
 segnosaurs and ornithomimosaurs and troodontids, which will help
 considerably; but I do know that most of the characters linking segnos
 and ornithoms are cranial, which cannot be discounted on a basis of
 the pes and pelvis. >>

Dinosaurian cranial features are quite plastic (particularly shapes of outer
bones with horns, crests, and frills), good for separating genera and species
at low taxonomic level but not nearly so good for distinguishing higher-level
taxa with longer lineages in which cranial features may change considerably.
I'd weight cranial features less than postcranial features in analyses, but
present cladistic methodology takes dim view of character weighting. Whole
question needs more study. I note also several errata and/or lack of clarity
(at very least) in study of _Erlikosaurus_ skull by Clark et al. that make
skull and thus genus seem more theropod-like than warranted. _Erlikosaurus_
basicranium quite distinct from that of most theropods but quite similar to
that of some prosauropods for which basicranium has been studied.