The 62-million-year-old fossil, described in the London-based Proceedings of Royal Society B research journal, is part of the Dyrosauridae group, which replaced mosasaurs, or serpentine marine lizards, as the dominant marine predators in the Palaeocene epoch.

"Based on the discovery, we know that's what happened near the Brazilian coast. Now the question is whether the same happened worldwide. We believe it did," said Alexander Kellner of the National Museum in Rio de Janeiro.

Guarinisuchus is derived from the word "warrior" in Brazil's Tupi Indian language. Munizi is a tribute to Brazilian palaeontologist Geraldo da Costa Barro Muniz.

With the skull, jaw and vertebrae, the fossil is the most complete of its group found in South America.

"One of the reasons we called it a warrior is because it survived the phenomenon that made dinosaurs extinct ... and they were the dominant predators even though this one was relatively small, at 3 meters in length. But we know the size isn't always important, just take the piranha fish," Kellner told Reuters.

The fossil was found in the coastal Mina Poty area in north-eastern Brazil.