LAST ONE IN THE WATER

The image below is a photo of the exhibit panel. Following it is a transcript of the panel.

Photo of the panel from the exhibit.

Mosasaurs were marine lizards, and the last group of giant, ocean-dwelling reptiles.

Teeth marks on ammonite shells indicate that these huge reptiles fed upon squids and their relatives. The largest one known was over 50 feet long! During the Age of Dinosaurs, mosasaurs thrived in vast shallow seas that covered much of what is now the Great Plains region of North America.

mosasaurs ( MOZE -ah-sorz): extinct relatives of some modern lizards

New features:

  • four flippers used for swimming
  • long, flat tail used for propulsion
  • long body: backbone (with more than 28 vertebrae) undulated for swimming
  • bony eardrum: calcified tympanic membrane picked up underwater sound vibrations, protected inner ear from pressure changes

When? 100 to 65 million years ago

Deep Divers?
Paddle and body shapes suggest that some species of mosasaur were surface swimmers, and others were deep divers. It has been proposed that apparent bone disease in some mosasaur fossils might have been caused by "the bends" -- nitrogen bubbles forming in the tissues as a result of surfacing from a deep dive too quickly.

PICTURE CAPTIONS:

  • Like a scene in a strange underwater ballet, a sea turtle races for its life, pursued by a gigantic mosasaur.
  • Diagram showing common ancestry and evolution of mosasaurs, ichthyosaurs, and plesiosaurs from organisms with two holes in skull behind the eye.