Stuff on gliding vs non-gliding (was Re: Protoavis (was Re: solnhofen)

["Tim Williams" <twilliams_alpha@hotmail.com>]

Silvio Renesto wrote:

> I do not deny  that some small drepanosaurids might have been gliders, but
> I did not consider  any postcranial feature representing a good evidence
> for gliding as for, say,  Icarosaurus. However, who knows? How different is
> the skeleton of a gliding ringtail  marsupial from that one of a
> non-gliding ringtail?


Certain studies have claimed that modern gliding mammals (by that I mean 
true patagial gliders, as opposed to modern leaping primates) do show 
certain derived *skeletal* traits not seen in non-gliding relatives.  The 
absence of these traits has been used to challenge a gliding ecology 
suggested earlier for the extinct paromomyids (Primates?).


Thorington, R.W., Jr (1984).  Flying squirrels are monophyletic.  Science 
225 (4666): 1048-1050

Hamrick, M.W., Rosenman, B.A., and Brush, J.A. (1999).  Phalangeal 
morphology of the Paromomyidae (?Primates, plesiadapiformes): The evidence 
for gliding behavior reconsidered.  American Journal of Physical 
Anthropology. 109 (3): 397-413.


But, to answer Renesto's original question, I'm not personally aware of any 
skeletal specializations seen in marsupial gliders that are not seen in 
closely related, non-gliding marsupials (such as _Pseudocheirus_).  Same 
applies to the scalytail genus _Zenkerella_.  This is the one anomalurid 
that does not glide (and so does not possess a gliding membrane).  I don't 
know if its lack of gliding specializations is primitive or derived (a 
secondary loss) compared to gliding scalytails.

Gliding behavior has been described in many mammal groups, including the 
colugos ("flying lemurs"; Cynocephalidae), several phalangeriform marsupials 
(Petauridae, Acrobatidae, _Schoinobates_ - all possibly independently 
acquired), and many rodents (flying squirrels [Petauristinae], scalytails 
[Anomaluridae], dormice [Gliridae] - again, all convergent for this 
behavior).

Direct evidence of a gliding membrane (patagium) has been described in at 
least one extinct rodent (an eomyid).  I'll check if this rodent shows the 
skeletal specializations that are believed to be necessary for gliding.


Tim

------------------------------------------------------------

Timothy J. Williams

USDA/ARS Researcher
Agronomy Hall
Iowa State University
Ames IA 50014

Phone: 515 294 9233
Fax:   515 294 3163

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