Saichania and Giganotosaurus

No other dinosaur was as well armoured as the Saichania. Thick bony plates protected it against predatory dinosaurs such as the Giganotosaurus, the second largest carnivorous dinosaur.

The Saichania was as heavily armoured as a knight in his heavy suit of armour. Instead of metal, it had thick, impenetrable bony plates all over its body; even on its head and under its belly. Sharp spikes on its back and head also provided it with protection. To defend itself, it would hurl its club-shaped tail with great force against its attackers. In contrast, the Giganotosaurus used its long, narrow tail the way a tightrope artist uses a balancing pole. This enabled it to maintain its balance when walking. 

The Giganotosaurus was 12-13 meters long, but its brain was no bigger than a cucumber.