Plotosaurus

Plotosaurus benni soni in a live reconstruction

• North America (California )

Plotosaurus ( = swimming lizard; Syn: Kolposaurus ) is a genus of mosasaur from the Late Cretaceous. Originally two species have been described benni P. andersoni and P. tuckeri. The types are named after the discoverers of the fossils A. Benninson and WM Tucker. A new study of the type material of both species revealed by now that only the type Plotosaurus has benni soni validity and P. tuckeri is a junior synonym.

Features

Plotosaurus was a tall, 10 to 13 meters long and long-tailed mosasaurs. His body was short and high, the tail had 64 vertebrae and was increased by the extension of the flat at the end of the spinous processes. The fingers and toes of the limbs were close together and formed a rigid wing-like fin. The fins were long and narrow, the number of finger bones of the single finger has increased ( Hyperphalangie ).

The skull was slender, reaching a length of 53 cm. The area occupied by many small, sharp teeth muzzle was pointed. Eyes and nostrils were large. Overall, Plotosaurus approached with his modifications of the skull, fins and tail to his time has long been extinct ichthyosaurs and was probably the fastest floating mosasaurs. He lived perhaps similar to those of smaller prey, which he pursued in deeper water. The stomach fossil obtained shows signs of the remains of fish. Of all the mosasaurs Plotosaurus shows the highest degree of adaptation to the oceanic habitat.

A newly found Plotosaurus skeleton in which even parts of the skin are preserved in three dimensions is the first time insight into the structure of the skin of a progressive mosasaur. The skin is covered with keeled and possibly reinforced with osteoderms shed. The scales cover probably led to a reduction of the surface resistance during fast swimming, similar to the effect the anvil- shaped placoid scales of sharks.