Scott Mardis sent this to me and it is a very valuable resource. The entire article can be downloaded from the site
http://mds.marshall.edu/etd/274/
Cryptoclidus' torso is unusually steep-sided for a Plesiosaur and it indicates some better degree of vertical movement at the surface, for surfacing, poking its head up, and then going straight down again.
The Saint-Fancois-Xavier sighting evidently has the animal showing a rear fin as it rolls and here is a version of the Plesiosaur in that position:
I am adding this now as a start of a more in-depth analysis to bee built up later over time, but what is here so far does look very promising.
Cryptoclidus is the genus with a body shape most like what we are after and the others do not concern us just now
Cryptoclidus' torso is unusually steep-sided for a Plesiosaur and it indicates some better degree of vertical movement at the surface, for surfacing, poking its head up, and then going straight down again.
Emerging the last one just a little more and allowing for the neck flexibility we already know was in there, we can have the animal in virtually any "Periscope" position the sightings actually suggest
Another one of my colleagues calls the animals in the vertical-periscope position "Bobbers" and I think it is a good term. In reviewing the cases, we found many examples. The foreflippers can be spread out at the sides for stability when in this position. 15-20 feet is a common height reported
The Saint-Fancois-Xavier sighting evidently has the animal showing a rear fin as it rolls and here is a version of the Plesiosaur in that position:
