Re: Plesiosaurs Necks

[Michael Habib <mhabib5@jhmi.edu>]

> I guess high rate of speed was a poor choice of words. Perhaps I 
> should have said ANY rate speed instead.
>
> The idea that they were fast is based on the basic aerodynamic design 
> of the flippers, as well as their size and positioning on the body. 
> The dual flippers appear to me to be capable of moving the body 
> swiftly through the water and allowing it to change directions very 
> abruptly.

For swimming ability predicted from flipper geometry, I would recommend 
taking a look at:

O'Keefe, F. (2001) Ecomorphology of plesiosaur flipper geometry. 
Journal of Evolutionary Biology 14 (6) : 987-991

O'Keefe, F. R. (2002) The evolution of plesiosaur and pliosaur 
morphotypes in the plesiosauria (reptilia: sauropterygia): 
Paleobiology, v. 28, n. 1, p. 101-112.

F. R. O'Keefe and M. T. Carrano (2005) Correlated trends in the 
evolution of the plesiosaur locomotor system Paleobiology, 
December 1, 31(4): 656 - 675.


In general, elasmosaurids and other long-necked plesiosaurs appear to 
have flipper shapes optimized for efficient, long-distance cruising 
(rather than particularly sustained speed or burst speed).  Just having 
large flippers does not make an animal fast (actually, extra large 
flippers would be expected in slow swimmers, not fast ones) and having 
two pairs may or may not contribute significantly to rate of travel.  
Elasmosaur flippers do tend to have pretty high aspect ratios; good for 
efficiency.

Pliosaurs, incidentally, drop out in the above studies as being more 
speed oriented.

Cheers,

--Mike Habib