Plesiosaur

"near-reptile"

EARLY JURASSIC TO CRETACEOUS PERIOD

220 million - 65 million years ago

Plesiosaurs were magnificent ocean-dwelling reptiles that "flew" gracefully through the water with massive paddles.  They were around almost as long as the dinosaurs from the Triassic period 220 million years ago until the end of the Cretaceous 65 million years ago.  Their remains have been found on every continent.  First discovered in the Jurassic formation of Lyme Regis in England in 1820, the name meaning "near-reptile" was meant to differentiate the understanding that these creatures were more reptilian than the fish-like Ichthyosaurs discovered in the same region.  

The order Plesiosauria are a large and varied group which have been broadly divided into two superfamilies based on their overall body structure.  The long-necked, small-headed PLESIOSAURS make up one superfamily named Plesiosauroidea and the short-necked, large-headed PLIOSAURS comprise the other superfamily named Pliosauroidea.

Plesiosaurs were one of the first kinds of extinct animal known to science, and were described as early as 1821.  The smallest were about 2m long as adults, the largest were enormous pliosaurs up to 20m long, comparable in size or even bigger than sperm whales ( Physeter ). They were possibly the biggest predators of all time, though remains of these giants are rare and fragmentary, and much research remains to be done.  

Pliosaurs first emerged in the Early Jurassic Period.  They were among the chief predators of the ancient seas, attacking large sharks, ichthyosaurs and even their relatives, plesiosaurs.  

Pliosaurs had a large head with very strong teeth and jaws.  Their teeth are deeply rooted in powerful jaws backed by extremely large jaw muscles.  

We can learn about what they ate from the fossils.  Occasionally stomach contents are found with well-preserved specimens, showing that some at least fed on belemnites and ammonites.  Other specimens show bite marks from larger predatory forms.  There is a wide range in tooth shape, showing that they were adapted to feeding on different types of prey.  Long, slender teeth may have been used to rake through sea-floor sediments in the way a swan dabbles on pond bottoms.  Larger, more robust teeth seem to be adapted for feeding on armored fish and cephalopods.  Some of the bigger pliosaurs had enormous, dagger-like teeth which were used to attack their smaller relatives.  

A plesiosaur used stones in it's stomach known as gastroliths.  These made it possible for them to swallow their food whole, letting the gastrolith grind the food.  The stones may also have served as ballast or weight for deep diving.

Common misspellings:  Pleosaur, Pleosaurus, Plyosaur, Plisiosaur, Pliosor, Plesiosor. 

The incredible masterpieces above were done by FRANK DENOTA and TODD MARSHAL.  Special thanks are due both these talented gentleman for permission to feature their art in this section.  Excerpts of this text by Richard Forrest.

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