The species grew up to two meters (six feet) in length and lived in lakes and rivers, University of Edinburgh researchers said.
The team said the species, given the name Metoposaurus algarvensis, was part of a wider group of primitive amphibians that were widespread at the time but became extinct. They are the ancestors of modern amphibians such as frogs, and are believed by paleontologists to have lived at the same time the dinosaurs began their dominance.
It was at the top of the food chain, feeding mainly on fish, but it was also a danger for newly appeared dinosaurs and mammals that strayed too near the water, Brusatte said.
The team says the find establishes that this group of amphibians lived in a more diverse geographic area than had been thought.
The dig began in 2009 and took several years. The "super salamander" bones were uncovered in a half-meter thick layer of rock in a hillside that is "chock-full" of bones, Brusatte said. The team hopes to raise funds to continue excavating the site.