The oldest known species of crocodile had an armour-plated head and a body half the length of a subway car, according to research released by US scientists who identified the now-extinct creature.

Nicknamed “Shield-croc” for its impressive head plate, the aquatic reptile swam in the waters of Africa some 95 million years ago and is the newest discovery of an ancient crocodile species, said the study in the journal PLoS ONE.

University of Missouri anatomy professor Casey Holliday identified the croc, Aegisuchus witmeri, by studying a fossilised partial skull specimen that was first discovered in Morocco.

The croc’s shield was likely used as a way to intimidate foes, attract mates and even control its head temperature, researchers said.

Its head was considerably flatter than other known species of crocodile.

Given the creature’s relatively thin jaws, Shieldcroc mostly ate a diet of fish, and probably did not use his armoured head as a fighting weapon but rather as camouflage.

“We believe Shield-croc may have used its long face as a fish trap,” said co-author Nick Gardner, an undergraduate researcher at Marshall University in West Virginia.

“It is possible that it lay in wait until an unsuspecting fish swam in front of it. Then, if it was close enough, Shield-croc simply opened its mouth and ate the fish without a struggle, eliminating the need for strong jaws.”

An analysis of the croc’s head size compared to other known creatures led the team to believe it likely boasted a 1.5-metre-long head and a nine-metre-long body.

The croc would have shared the earth with the many dinosaurs that thrived during the Late Cretaceous Period in the Mesozoic Era, which has been referred to as the “Age of the Dinosaurs”.