Re: New paper on the origin and early evolution of dinosaurs

[Tim Williams <tijawi@yahoo.com>]

David Peters <davidpeters@att.net> wrote:


> As long as you include Lagerpeton and Dromomeron, and
> especially pterosaurs, as dino-sisters, you're going to have
> trouble with the origin of dinos.


Sorry, I really don't get what you mean here.  The positions of _Lagerpeton_ 
and _Dromomeron_ as "dino-sisters" (i.e., non-dinosaurian dinosauromorphs) are 
recovered by phylogenetic analysis.  I can't understand what could be gained by 
excluding them from an analysis.


Speaking of pterosaurs, it's possible that the evolution of the pterosaur body 
plan, especially the evolution of wings, occurred quite quickly.  Such a rapid 
transformation has been inferred for the bat (chiropteran) body plan, and used 
to explain why we haven't yet found fossil evidence for the early stages of 
flight development in this group (Sears et al., 2006; PNAS 103: 6581â6586).  


It is therefore possible that pterosaurs might have branched off quite late, 
around the same time as the dinosaurs.  In fact, maybe pterosaurs are 
themselves dinosaurs.  I'm going to stick my neck out here and say that I 
wouldn't be at all surprised if future analyses show pterosaurs to be nested 
inside Saurischia.  It would mean that the axial air sacs (and flow-through 
respiratory system) shared by saurischians and pterosaurs have a single origin. 
 It's a crazy idea, I know.  But not *that* crazy.


Returning to the actual paper, it's nice to see Silesauridae receive a formal 
definition.  It's also worth mentioning that several Triassic dinosaur taxa 
mentioned by Langer &c have been hypothesized elsewhere (Ezcurra & Novas, 2009; 
JVP 29: 92A) to belong to a new clade called the Guaibasauridae 
(_Guaibasaurus_, _Panphagia_, _Saturnalia_, _Agnosphitys_), a radiation of 
basal sauropodomorphs. 


Cheers

Tim