Pliosauroidea

Pliosauroidea is an extinct group of ancient sea reptiles called plesiosaurs that lived from the latest Triassic to the early Late Cretaceous. They are most famous for a subgroup called Thalassophonea, which had short necks, big heads, and strong jaws filled with sharp teeth—much like modern crocodiles. These creatures were excellent hunters in the ocean.

Unlike other plesiosaurs with long necks, pliosauroids had short necks and long heads, with larger back flippers than front ones. They were carnivorous, meaning they ate meat, and they could grow from 4 to over 10 meters long. They likely hunted fish, sharks, ichthyosaurs, and even other plesiosaurs.

Some of the biggest pliosauroids included Kronosaurus, Sachicasaurus, Monquirasaurus, and Pliosaurus. Other well-known types were Rhomaleosaurus, Peloneustes, Liopleurodon, and Macroplata. Fossils of these amazing animals have been discovered in Africa, Australia, China, Europe, North America, and South America.

Name

Pliosauroidea was named by Welles in 1943. The name comes from the genus Pliosaurus, which means "more lizard" in Greek. The word Pliosaurus was created in 1841 by Richard Owen. He thought it showed a connection between plesiosauroids and crocodilians because of their crocodile-like teeth.

Classification

The classification shown here is based on a study from 2011 by scientists Hilary F. Ketchum and Roger B. J. Benson.

• Suborder Pliosauroidea
  • Eurysaurus?
  • Sinopliosaurus?
  • Family Rhomaleosauridae
    • Archaeonectrus
    • Bishanopliosaurus?
    • Borealonectes
    • Eurycleidus
    • Macroplata
    • Maresaurus
    • Meyerasaurus
    • Rhomaleosaurus
    • Sthenarosaurus
    • Yuzhoupliosaurus?
  • Family Pliosauridae
    • Anguanax
    • Attenborosaurus
    • Eardasaurus
    • Gallardosaurus
    • Hauffiosaurus
    • Liopleurodon
    • Marmornectes
    • Megalneusaurus
    • Pachycostasaurus
    • Peloneustes
    • Pliosaurus
    • Rhaeticosaurus
    • Simolestes
    • Thalassiodracon
    • Subfamily Brachaucheninae
      • Brachauchenius
      • Kronosaurus
      • Luskhan
      • Makhaira
      • Megacephalosaurus
      • Monquirasaurus
      • Polyptychodon
      • Sachicasaurus
      • Stenorhynchosaurus

Pliosauroidea is a group that includes all animals more closely related to Pliosaurus brachydeirus than to Plesiosaurus dolichodeirus. Both Pliosauridae and Rhomaleosauridae are also defined in similar ways. The family tree shown here comes from the 2011 study by Ketchum and Benson.

Large pliosauroids

Some pliosauroids, all in Pliosauridae, grew very big—over 10 meters long—making them the largest of all plesiosaurs, though some elasmosaurs were longer because of their long necks.

In 2002, a very large pliosaur was found in Mexico and called the "Monster of Aramberri". Its remains, found in 1985, included part of a backbone and teeth. In 2006, scientists from the University of Oslo found a giant pliosaur in Svalbard, near the North Pole. This discovery was shown on a History TV show called Predator X. In 2009, an even bigger pliosaur was found near Weymouth, in Dorset, on Britain’s Jurassic Coast. In 2023, another very complete pliosaur skull was found on the Dorset coast and was featured in a PBS documentary with David Attenborough.