|Home time period||Early Cretaceous|
|Creature type||Thyreophoran Dinosaur|
|Appearances||The Lost Island|
It appears when the ARC team run into a sleeping herd when marooned in the past. Cutter carefully manages to move the team around the sleeping herd and later the team observes a herd of them associating with Iguanodons.
- Polacanthus made an appearance in Walking with Dinosaurs.
- Polacanthus is the first armored dinosaur to be encountered.
- Its name means "Many Thorns".
- Polacanthus is the first creature to be in a herd.