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ZoomDinosaurs.com
Dinosaur and Paleontology Dictionary
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Click on an underlined word for more information on that subject.
If the dinosaur or paleontology term you are looking for is not in the dictionary, please e-mail us.

PLESIOSAURS
"Near-lizards"


Plesiosaurs (meaning "near lizard") were flippered marine reptiles from the Mesozoic Era - they were not dinosaurs. Plesiosaurs are divided into two groups: the Plesiosauroids with long, snake-like necks, tiny heads, and wide bodies, and the Pliosauroids, which had large heads with very strong jaws and short necks.

ANATOMY
Thalassomedon, Jim Puckett
Thalassomedon
,
photo by Jim Puckett
Plesiosaurs were large, marine reptiles from the Mesozoic Era that ranged in size from 8-46 feet long (2.5-14 m). They had four flippers, sharp teeth in strong jaws, and short, pointed tails. Plesiosaurs may have evolved from the Nothosaurs or Pistosaurus, a mid-Triassic reptile.

No one knows how the long-necked plesiosaurs held their necks; either they held the neck horizontally, or else it was supple and could move readily.

WHEN PLESIOSAURS LIVED
Plesiosaurs lived during the Mesozoic Era, from the early Jurassic to the end of the Cretaceous.

BEHAVIOR
Plesiosaurs lived in the open oceans and breathed air. Some Plesiosaurs have been found with small stones in their stomachs; these may have been used to help grind up their food, or as ballast, to help them dive. They probably laid eggs in beach sand (like modern-day sea turtles).

REPRODUCTION
Plesiosaurs may have laid eggs in nest that they dug into the sand, much as modern-day sea turtles do.

DIET
Plesiosaurs ate fish and other swimming animals. They had strong jaws and sharp teeth.

LOCOMOTION
Plesiosaurs swam using their four paddle-like flippers in a manner similar to that of modern turtles. They might have been able to move a little bit on land, as modern seals do.

CLASSIFICATION
Plesiosaurs are reptiles, but not dinosaurs. They are:

DISCOVERY OF FOSSILS
Plesiosaur fossils were discovered over 200 years ago, long before any dinosaurs were unearthed. Many Plesiosaur fossils were found between 1800 and 1821 by Mary Anning, the first professional fossil hunter. Plesiosaurus was named by W.D. Conybeare in 1821. Plesiosaur fossils have been found all over the world in Cretaceous and Jurassic sediment.

PLESIOSAUR ACTIVITIES AND LINKS
A Liopleurodon printout
A Plesiosaurus printout
An Elasmosaurus printout
Elasmosaurus information sheet from Enchanted Learning.
Kronosaurus information sheet from Enchanted Learning.
Plesiosaur fossils at the UCMP, Berkeley.



Information Sheets About Dinosaurs
(and Other Prehistoric Creatures)

Just click on an animal's name to go to that information sheet. If the dinosaur you're interested in isn't here, check the Dinosaur Dictionary or the list of Dinosaur Genera. Names with an asterisk (*) were not dinosaurs.
How to write a great dinosaur report.

For dinosaur printouts, click here.

For brief dinosaur fact sheets, click here.




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