Re: questions about the Odontochelys study

[Mike Habib <habib@jhmi.edu>]

Augusto Haro wrote:

> > >
> All right, but it was just an example that turtles with a heavy
> cuirass are relatively fast, and that I doubt that turtles with less
> completely covering shells, as the snapping, can really be faster.
> Just to say I do not know exactly to what is decreased coverage of the
> bony shell in turtles related.


Is there a particular reason that you doubt a chelydrid could be  
faster?  In any case, the shell reduction, especially in the plastron,  
might have more impact on aquatic locomotion than terrestrial  
walking.  For mata-matas, as least, the plastron reduction allows the  
animals to take a somewhat more erect stance when punting along the  
bottom, and appears to greatly increase effective stride and speed  
(they're actually quite rapid movers when need be).  This is all  
unpublished, personal observation, however (albeit many years of  
personal observ. for that particular taxon).

For pelagic aquaflyers, specifics of shell reduction or expansion  
might be related to required forelimb excursions, as well as the  
specific bracing important for mirrored stroke utilization (I  
recommend taking a look at Stephen Godfrey's 1984 manuscript on  
plesiosaur locomotion and aquaflying).

Cheers,

--Mike


Michael Habib, M.S.
PhD. Candidate
Center for Functional Anatomy and Evolution
Johns Hopkins School of Medicine
1830 E. Monument Street
Baltimore, MD 21205
(443) 280-0181
habib@jhmi.edu