Teratorns (from the Greek Τερατορνις Teratornis, 'monster bird') are an extinct group of very large birds of prey that lived in North and South America from the Miocene through Pleistocene epochs. They include some of the largest known flying birds. Argentavis, the largest known variety of Teratorn, had an estimated wing span of 7 m (23 ft), a height of circa 1.5–2 m (4.9–6.6 ft), and a mass of approximately 70–72 kg (154–159 lb). (The possibly larger Pelagornis has not yet been completely examined.) Teratorns' interactions with Pleistocene humans may have inspired the Native Americans' legend of the Thunderbird.