Water Dinosaur Names: Sea Creatures of the Prehistoric World
When most people think of water dinosaur names, they picture giant creatures lurking in ancient seas â and they are not wrong. During the age of dinosaurs, the oceans were ruled by some of the most impressive reptiles that ever lived. Names like Mosasaurus, Plesiosaurus, and Ichthyosaurus belong to creatures that were every bit as fearsome as T. rex, just wetter.
Here is an important detail that surprises a lot of kids: these animals were not technically dinosaurs. Dinosaurs lived on land. The creatures on this page were marine reptiles â a separate group that evolved to live in the ocean while dinosaurs ruled the land. But they all lived during the same prehistoric era, and their names follow the same Latin and Greek patterns that make dinosaur names so fun to learn.
On this page, you will find the most well-known prehistoric sea reptiles, how to say their names out loud, and what those names actually mean. Mosasaurus means "Meuse River lizard." Ichthyosaurus means "fish lizard." Plesiosaurus means "near lizard." Every name tells a story about the animal â where it was found, what it looked like, or how it moved through the water.
Whether you are a kid who just watched a nature documentary or a parent helping with a school project, this guide gives you accurate names, correct pronunciations, and enough cool facts to impress anyone at dinner.
Click any name to hear how to say it
Mosasaurus
MOH-za-SORE-us
Elasmosaurus
eh-LAZ-moh-SOR-us
Ichthyosaurus
IK-thee-oh-SOR-us
Plesiosaurus
PLEE-zee-oh-SOR-us
Liopleurodon
LIE-oh-PLOOR-oh-don
Nothosaurus
NO-tho-SORE-us
Cryptoclidus
krip-TOE-klid-us
Kronosaurus
KRON-oh-SORE-us
Ophthalmosaurus
off-THAL-mo-SORE-us
Shonisaurus
SHO-nee-SOR-us
Temnodontosaurus
tem-no-DON-to-SOR-us
Cymbospondylus
SIM-bo-SPON-dih-lus
Futabasaurus
foo-TAH-bah-sore-us
Hydrotherosaurus
HY-dro-thero-SORE-us
Globidens
GLOB-ih-denz
Clidastes
CLY-das-teez
Eurhinosaurus
yoor-RY-no-SOR-us
Macroplata
MAK-ro-PLAH-tah
Why Do These Prehistoric Sea Creature Names Sound So Strange?
Almost every prehistoric sea reptile name comes from ancient Greek or Latin â languages that scientists have used to name species for hundreds of years. When a paleontologist discovers a new creature, they build a name from root words that describe something about the animal. That is why the names can look impossible to read at first glance, but once you know the roots, they make perfect sense.
Take Mosasaurus (moh-zah-SAWR-us). It is named after the Meuse River in the Netherlands, where the first fossil was found, plus the Greek word saurus, meaning lizard. Or consider Ichthyosaurus (ik-thee-oh-SAWR-us), built from ichthys (fish) and saurus (lizard) â a fish-lizard, which is a pretty accurate description of an animal shaped almost exactly like a dolphin.
Plesiosauria (plee-see-oh-SAWR-ee-uh) comes from the Greek plesios, meaning near or close to, because early scientists thought these animals were a stepping stone between land reptiles and sea creatures. Elasmosaurus (ih-LAZ-moh-sawr-us) gets its name from the Greek elasmos, meaning plate or thin layer, referring to the flat bones in its neck vertebrae.
Once you learn that saurus always means lizard or reptile, and that the first part of the name usually describes where it was found or what it looked like, these long words become much easier to decode â and a lot more interesting.
Fun Facts About Prehistoric Ocean Reptiles Worth Knowing
Mosasaurus could grow longer than a school bus â some reached 17 meters (56 feet). They were not slow, graceful swimmers either. Scientists believe mosasaurs moved through the water by swinging their tails side to side, similar to modern crocodiles, and could burst forward quickly to ambush prey.
Ichthyosaurs are one of the most remarkable examples of convergent evolution in all of natural history. They were reptiles, but their bodies evolved to look almost identical to dolphins â streamlined shape, dorsal fin, flippers, and all. They even gave birth to live young in the water rather than laying eggs on shore.
Elasmosaurus had one of the longest necks of any animal ever discovered, with over 70 neck vertebrae. (For comparison, almost all mammals, including giraffes, have exactly 7.) When the first fossil was assembled in 1868, the scientist in charge accidentally put the head on the tail end â an embarrassing mistake that was not caught for several years.
Pliosaurus (PLY-oh-sawr-us) was a shorter-necked relative of Plesiosaurus with a skull nearly 2 meters long and a bite force that some researchers estimate surpassed that of T. rex. The prehistoric ocean was not a safe place.