A dinosaur-age ancestor of modern crocodiles from Morocco had a huge armoured head designed as a "fish trap", scientists have revealed.
The extinct creature, dubbed "Shieldcroc", lived around 95 million years ago but was unlikely to have wrestled with dinosaurs.
Instead, it probably used its long flat jaws to ambush fish.
"We believe Shieldcroc may have used its long face as a fish trap," said undergraduate researcher Nick Gardner from Marshall University in the US.
"It is possible that it lay in wait until an unsuspecting fish swam in front of it. Then, if it was close enough, Shieldcroc simply opened its mouth and ate the fish without a struggle, eliminating the need for strong jaws."
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The crocodile, officially called Aegisuchus witmeri, is the earliest ancestor of modern crocodiles to be found in Africa.
The new study was conducted on a fossilised partial skull specimen unearthed in Morocco several years ago and now housed at a Canadian museum.
Scientists calculated that the creature was about nine metres long with a 1.5 metre head bearing a shield-like structure never before seen in crocodiles.
The shield may have been used to attract mates and intimidate enemies, or as a thermo-regulator to control head temperature.
Dr Casey Holliday, from the University of Missouri, US, said: "Today's crocodiles live in deltas and estuaries, the environments put under the most stress from human activity.
"By understanding how these animals' ancestors became extinct, we can gain insight into how to protect and preserve the ecosystems vital to modern crocodiles."
