An article for anyone interested in the lifestyle of mosasaurs......
http://news.nationalgeographic.com/news/2013/09/130910-mosasaur-sea-monster-reptile-tail-ocean-science/
Mosasaurs are usually depicted as having tapering tails like modern lizards, but the fossil of Prognathodon from Jordan shows that mosasaurs had a tail fin like modern day sharks. This discovery may have to force dino-artists to depict mosasaurs with shark-like fins, and it also reminds me of another study (http://www.theguardian.com/science/blog/2010/sep/01/mosasaur-evolution-dinosaurs) showing that the plioplatecarpine Platecarpus had a tail supporting a fin like that of ichthyosaurs and metriorhynchids.