Mastodonsaurus

Mastodonsaurus (meaning "teat tooth lizard") is an extinctgenus of temnospondylamphibian from the Middle Triassic of Europe. It remains one of the largest amphibians known in the fossil record, and may have exceeded 6 meters (20 feet) in length. Mastodonsaurus belongs to a Triassic group of stereospondyl temnospondyls called Capitosauria, characterized by their large body size, large flattened skulls, and probably predatory aquatic lifestyles analogous to some later crocodilian reptiles.

The gigantic size of Mastodonsaurus made it a top predator in lakes, swamps, river deltas, and other freshwater and brackish aquatic ecosystems. Huge jaws equipped with enlarged fangs and tusks, along with a powerful tail, suggest it was an underwater ambush hunter. Mastodonsaurus would have preyed mainly on fish and on smaller amphibians, but likely took on terrestrial animals that ventured into water as well. Given its heavy body mass and its relatively small limbs, Mastodonsaurus likely could not crawl onto land after reaching larger growth stages.