Its skull was short and broad, and it had a narrow snout and deep powerful jaws. It had heavy-duty armour consisting of rows of plates covered its long back. It was the top carnivore of the age. It had a unique upright stance with straight legs directly beneath its body suggesting a quick and efficient runner. It had longer back legs than front legs.
Some palaeontologists believe it ran on two legs, but the majority think that it did so on four.
It was on the line to crocodiles, but it was not a crocodile itself. The Fact Files, Family Tree and Glossary have been written in consultation with leading palaeontologist Michael Benton, Professor of Vertebrate Palaeontology at the University of Bristol, and represent the latest scientific knowledge about these creatures.