Clarke, J.A., Olivero, E.B., and Puerta, P. (2003). Description of the
Earliest Fossil Penguin from South America and First Paleogene Vertebrate
Locality of Tierra Del Fuego, Argentina. American Museum Novitates 3423:
1?18.
I wasn't aware that any flying stem
Sphenisciformes had been discovered - or has _Manu_ or some other
procellariiform fossil been reassigned?
What is _Manu_?
AFAIK no pre-flightless pansphenisciform is known. That would indeed be a
wonderful discovery (I would guess that the postcranium of these ur-penguins
would be superficially very puffin-like, with the wings adapted for both
flying and swimming). At the moment Pansphenisciformes and Sphenisciformes
are equivalent in content since all known penguins and their stem relatives
are flightless. Sphenisciformes is more inclusive than Spheniscidae because
certain fossil sphenisciforms appear to lie outside the crown group.
As Jaime alluded to, the proposed definition of Sphenisciformes ("loss of
aerial flight homologous with that of extant penguins") is fraught with
problems. Even if we had these transitional taxa, would we be able to pin
down exactly when aerial flight was lost? It's like Gauthier and de
Queiroz's proposed definition of Avialae ("having wings associated with
powered flight") except in reverse. The same problem applies: defining a
clade based on a behavior that is unpreservable and based entirely on
ecomorphological inference.
Tim
_________________________________________________________________
Looking to buy a house? Get informed with the Home Buying Guide from MSN
House & Home. http://coldwellbanker.msn.com/