Re: PYGOSTYLES & PENGUINS

["T. Mike Keesey" <tmk@dinosauricon.com>]

On Wed, 23 Feb 2000 darren.naish@port.ac.uk wrote:

> By no means am I saying that either case (the evolution of penguins 
> or ratites from volant ancestors) is now made less secure by the 
> discovery of an apparent pygostyle in a non-avian theropod. Nor am I 
> saying that, now that at least one oviraptorosaur has an apparent 
> pygostyle then all oviraptorosaurs must also descent from volant 
> pygostyle-bearing ancestors. I am just pointing out some 
> inconsistency in argumentation, though I have no real point to make 
> here and have no interesting conclusion to draw.

Jaime Headden (I think) noted that _Pteranodon_ has a "pygostyle" a little
while back on this list. I also learned today while browsing around Dave
Peters' Pterosaur Homepage that _Drepanosaurus_ (a prolacertiform) has an
odd claw-like structure at the end of its tail that is probably fused
vertebrae (_Drepanosaurus_ has a lot of odd skeletal structures, actually
...)

So the fusing of vertebrae at the end of the tail seems to have happened
independently in at least four lineages of archosauromorph, and may have
had different purposes in each (_Pteranodon_'s certainly did not support
feathers; _Drepanosaurus_' looks like something to grab with; who knows
what Nomingis' was for?).

Which of these structures should properly be called pygostyles? Pygostylia
is a subclade of Aves...

-- T. Michael Keesey .................................. <tmk@dinosauricon.com>
   My Worlds (including The Dinosauricon) ... <http://dinosauricon.com/keesey>
   AOL Instant Messenger ........................................ <Ric Blayze>