Pliosaurs were some of the largest marine reptiles of all time.
They reached an acme in the Late Cretaceous with a variety of morphologies derived from smaller ancestors. Shown here are Trinacromerum, Brachauchenius and Kronosaurus, three taxa rarely shown together to scale. The big difference is in flipper size. It’s also worth noting the size of the girdles anchoring each flipper set. In whales, flipper size also varies greatly and not always for swimming advantage.
even closely related ones (Fig. 2), also had widely varying flipper sizes. Here we see ‘Cymbospondylus’ buchseri and the related Guizhouichthyosaurus. Both were probably sinuoous swimmers, rather than tail or flipper swimmers.
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