Meganeuropsis permiana was considered the largest insect of all time, it was a dragonfly relative with an estimated wingspan of around 710 mm (28 in). It existed before the dinosaurs, during the Artinskian age of the Permian period, 290.1–283.5 million years ago. There are several theories as to why insects were so big during this time. One theory was that oxygen levels in the atmosphere were significantly higher than today, although there is some controversy regarding this theory. Another theory was that insects at the time were at the top of the food-chain, with few predators.