Spinosaurus is a predator, but one that hunts in water.
It's ichthyophagous, a fish-eater.
This is Onchopristis.
An eight-metre-long giant swordfish, similar to those alive today.
The saw-like rostrum is lined with lethal barbs
and is, in itself, up to 2.5 metres in length.
It's thought they migrated into freshwater rivers to breed,
where the young may be safer, but the adults are exposed to new threats.
With their breeding season at its height, these rivers are filled with Onchopristis.
It's the perfect hunting opportunity for Spinosaurus.
Spinosaurus's conical teeth evolved to grip prey rather than tear off flesh.
For that, it needs powerful arms and claws.
With prey plentiful, Spinosaurus can afford to be wasteful.
A fact which other dinosaurs take full advantage of.
Rugops, an eight-metre carnivore.
Anywhere else, it might dominate.
But here it is dwarfed by Spinosaurus.
Spinosaurus is unique,
with long, narrow jaws and nostrils set high on its head.
Its teeth were straight and conical.
They gave us a clue as to how it killed.
More evidence came in 2008,
when Spinosaurus' skull was put through a CT scanner.
It revealed a curious pattern of holes and sinuses in the snout
that looked just like those of crocodiles.
It's thought these contained pressure sensors...
sensors that, like a crocodile, can detect prey,
making it perfectly adapted to hunting in water.
This discovery gives us our best evidence of exactly how it hunted.
Able to hold its snout in the water because of its high nostrils,
it can strike without even seeing its prey.