Arthropleura (Greek for "Rib Joint') was a 0.3–2.6 metre (1–8.5 feet) long relative of centipedes and millipedes, native to the Upper Carboniferous (340-280 million years ago) of what is now northeastern North America and Scotland. It is the largest known land invertebrate of all time, and would have had few predators.
What Arthropleura ate is a matter of debate among scientists, as none of the fossils have the mouth preserved. However, it is reasonably certain that it would have had a sharp and powerful set of jaws. Based on this assumption, it used to be thought that Arthropleura was carnivorous, but recently discovered fossils have been found with pollen in the gut, suggesting that the creature ate plants. It is possible that the smaller Arthropleura species were vegetarian, while the largest ones were omnivorous, using their jaws to tackle vegetation, as well as to hunt small animals and insects. It is estimated that the average Arthropleura could have eaten its way through a ton of vegetation a year.
Fossilized footprints from Arthropleura have been found in many places. These appear as long, parallel rows of small prints, which show that it moved quickly across the forest floor, swerving to avoid obstacles, such as trees and rocks. When moving at speed, its body would stretch and become longer, giving it a greater stride length and thus allowing it to move faster.
As it moved about, Arthropleura would have brushed against many different types of plant, and may have helped the forest reproduce by moving pollen or spores about the place. It is also thought that Arthropleura was capable of travelling under water, and that it may have returned to lakes and rivers in order to moult its shell. This would have made it vulnerable to attack by large fish and amphibians. On land an adult Arthropleura would have had few enemies.
Arthropleura evolved from crustacean-like ancestors in the Carboniferous, and was able to grow larger than modern arthropods, partly because of the high percentage of oxygen in Earth's atmosphere at that time, and because of the lack of large terrestrial vertebrate predators. Fossil tracks of an arthropod dating back to the Silurian are sometimes attributed to either Arthropleura, or a Silurian- to Early-Devonian millipede called Eoarthropleura. Arthropleura became extinct at the start of the Permian period, when the moist climate began drying out, destroying the rainforests of the Carboniferous, and allowing the desertification characteristic of the Permian. Because of this, oxygen levels in the atmosphere began to decline to more modest levels. None of the giant arthropods could survive the new dry, lower-oxygen climate. Its tracks have the ichnotaxon name Diplichnites cuithensis.