Subphylum : Myriapoda
Class : Arthropleuridea
Order : Arthropleurida
Family : Arthropleuridae
Genus : Arthropleura
Length : Up to 8.5ft (2.6m)
Status : Extinct for about 280 million years!
Arthropleura lived in forests during the Carboniferous Period between 340-280 million years ago. At this time oxygen levels were much higher than they are now, which allowed for insects to reach much larger sizes. Another contribution to their hugeness was a lack of large vertebrate predators. Arthropleura had a long, flat, segmented body with as many as thirty sets of legs. They were distant relatives of the millipedes that we have today, and they have the designation of being the largest land invertebrates of all time!
We've found a whole mess of fossilized Arthropleura footprints, as well as many fossils of the animals themselves. Scientists aren't completely sure of Arthropleura's diet, since we don't have full jaws left to study, but it was most likely a herbivore based on plant materials found in coprolites (fossilized excrement).
Near the end of the Carboniferous Period the world began to dry out and the forested habitats of Arthropleura begin to shrink. This in turn caused a decrease of oxygen in the atmosphere, and Arthropleura could no longer maintain its large body size. They eventually died out, along with their entire Class. Other myriapods exist in their place today, though they are of minuscule size by comparison, with the largest measuring up to 1 ft (30cm).