The Artheopleura is a relative of centipedes and millipedes that grew from 0.3-2.6 metres in length. It lived in the carboniferous period (340 to 280 million years ago). It is the largest known invertibrate of all time.
This creature had a powerful set of jaws but mostly ate plants and moved swiftly across the forest floors. The Artheopleura became the size it did because of a lack of predators and the huge amaount of oxygen in the air.