The Natural History Museum (NHM), La Brea Tar Pits Museum, and William S. Hart Museum will be closed until further notice to minimize the spread of COVID-19. Please check back for up-to-date information. See NHMLAC's response to coronavirus (COVID-19).

Mind-Blown Science: Dr. Luis Chiappe and NHM's Extraordinary Plesiosaur

Dr. Luis Chiappe, Director of our Dinosaur Institute, explains why this giant marine reptile blows his mind.

pregnant plesiosaur in dinosaur hall

Plesiosaurs were a diverse family of giant marine reptiles (not dinosaurs) that lived during the Mesozoic Era. They typically had broad bodies, short tails, and large flippers. They were among the top predators in the Western Interior Seaway, the large inland sea that existed during the Cretaceous period stretching from the Gulf of Mexico to the Arctic Ocean. 

This extraordinary mounted Plesiosaur skeleton in the Dinosaur Hall shows us a rare surprise. A closer look shows a baby’s skeleton inside her, showing scientists that Plesiosaurs had live births during the age of dinosaurs.