Ichthyosaur, marine reptile

"Getting a Meal
Some marine predators had needlelike teeth that pierced and held on to slippery prey like fishes or soft-bodied invertebrates. Others, such as Stenopterygius and Steneosaurus, had thicker, conical teeth to crush struggling prey.

The Shapes of Fast Swimmers
Although many ichthyosaurs resembled sharks and dolphins, they were actually reptiles. Thanks to convergent evolution, these unrelated animals evolved similar bodies because the demands of living underwater favored those shapes over others. Stiff, smooth bodies, tall dorsal fins, and strong tails allowed them all to be fast-swimming predators."