References on plesiosauria?

[bonebug@halcyon.com (Joe Small)]

Looking for the definitive resource on plesiosaurs.  We have *North American 
Plesiosauria; Williston, Samual W; 1903*, but no others.

Can anyone recommend additional reading, especially taphonomy?

A friend and I found a tooth, not dinosaur, not crocodile, not mosasaur (to 
the best of our knowledge).  Recurved, nearly round in section with a 
slight, posterior, longitudinal ridge.  Very dense.  The tip is missing, but 
we have the base 1.5 inch, and calculate the overall length at approx 3 
inches. Found with widely scattered and eroded cranial(?) material, 
characterized by concentric, elliptical cross-section.  Claggett -> Judith 
River transitional sandstones near Havre, Mt.  Any suggestions?
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Joe Small - Amateur Paleontologist &   Editor of 'Bone Bug Journal,
                                       Field Notes':
                                       Twice-monthly newsletter of
bonebug@halcyon.com                    amateur paleontology
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