PYGOSTYLES & PENGUINS

[darren.naish@port.ac.uk]

Thanks to a printing problem we are afflicted with here at the 
university, I have a bit of spare time and would like to regurgitate 
a random thought I had the other day.. well, not that random 
actually.

I read a lot about penguins. As some of you may know, I was actually 
supposed to be doing my phd on this group, and in fact Stig Walsh and 
I still intend to write up the several new taxa represented at the 
Pliocene Chilean bonebed Stig has been working on. To get to the 
point, it was argued by Lowe and some other authors in the 1930s that 
penguins were not secondarily flightless, but had actually evolved 
from non-volant ancestors. Similar arguments were advocated for 
palaeognaths. Simpson and all subsequent workers, however, showed 
that the evidence for this was weak and the structure of the penguin 
cerebellum, their courtship rituals, habitual postures and several 
other features indicated descent from flying ancestors analogous with 
extant diving petrels (pelecanoidids). Of interest here is that one 
of the primary pieces of evidence used for descent of penguins 
from volant ancestors was the presence of a pygostyle, as penguins 
clearly have this structure. It was argued that only volant birds 
have evolved a pygostyle, and that penguins have it must therefore 
mean that they, or their ancestors, once flew. De Beer, in a paper 
evaluating the descent of ratites from volant or non-volant 
ancestors, also cited the pygostyle as a flight feature retained 
vestigially as a 'heritage marker' in some extant ratites.

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.

Well, back to work.

DARREN NAISH 
PALAEOBIOLOGY RESEARCH GROUP
School of Earth, Environmental & Physical Sciences
UNIVERSITY OF PORTSMOUTH
Burnaby Building
Burnaby Road                           email: darren.naish@port.ac.uk
Portsmouth UK                          tel: 01703 446718
P01 3QL                               [COMING SOON: 
http://www.naish-zoology.com]