Trinacromerum

Trinacromerum is an extinct genus of sauropterygian reptile belonging to the plesiosaur suborder. It lived during the Late Cretaceous period in what is now Kansas.

Description
It was 3 meters (9.8 feet) long. Its teeth show it fed on small fish.

The long flippers of Trinacromerum enabled it to achieve high swimming speeds.[1] Its physical appearance was described by Richard Ellis as akin to a "four-flippered penguin."

Classification
Below is a cladogram of polycotylid relationships from Ketchum & Benson, 2011.