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Re: Plesiosaurs Necks



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