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Re: Plesiosaurs Necks
Dann Pigdon wrote:
Dinosaur World wrote:
This suggests to me that they were active, fast moving animals. What I don't
understand is if the necks were somewhat ridged, wouldn't this prevent them
from "snaking" their necks through the water in an attempt to catch prey?
Were fast moving fish not a big part of their diet?
Recent studies have suggested that bivalves made up part of the
That's one thing...
That's completely another. A single data point showing the use (at one
point of time and space) of a structure does _not_ make a functional
argument about either (1) the origin or (2) the maintenance (in
evolutionary terms) of same structure. For what it's worth (rather
little, probably), I don't think that elasmosaurids evolved that neck
simply to harvest benthos. The advantages of a long neck for catching
agile nekton seem too great to be ignored. But could a long neck be
used to pluck bivalves from the sea floor? Apparently so... Remember,
the animal that (I presume) you are referring to also had a fair amount
of nekton (belemnites) in its stomach content.
The long necks may have been for foraging back and
forth on the sea floor
(like underwater versions of diplodocids
Unless diplodocids were catching fish and cephalopods, I doubt that....
Lots of modern marine tetrapods manage to avoid their predators without
being faster than them. You can be clever, too....(or at least, have an
an evolution-refined behaviour that looks like cleverness).
I imagine you don't have to be all that fast to catch shell
fish either - just faster than anything that might want to eat YOU.
What do juvenile elasmosaurids look like? Could they have had relatively
Most likely, given basic patterns of allometry for amniotes.
(hence capable of faster evasive action)? Maybe, but maybe not. Reynolds numbers are affected by shape and size,
and larger animals are relatively more efficient swimmers than smaller
ones (as far as my limited understanding of the fluid dynamics goes -
please let me know if I've got this, as PB would say, 'bass ackwards').
changed from active persuit of prey to more passive bottom feeding as
they grew larger...
According to Joan Wiffen, more likely the other way around:
Wiffen et al., Ontogenetic evolution of bone structure in Late
Cretaceous Plesiosauria from New Zealand.Geobios 28, 625-40 (1995).
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