Greenland sharks live at least as long as 400 years, and they reach sexual maturity at the age of about 150, a new study reports. The results place Greenland sharks as the longest-lived vertebrates on Earth. The Greenland shark (Somniosus microcephalus) is widely distributed across the North Atlantic, with adults reaching lengths of 400 to 500 centimeters (13 to 16 feet). The biology of the Greenland shark is poorly understood, yet their extremely slow growth rates, at about 1 cm per year, hint that these fish benefit from exceptional longevity. Traditional methods for determining the age of a species involve analyzing calcified tissue, a feature that's sparse in Greenland sharks. Therefore, to determine the average age of this species, Julius Nielsen et al. applied radiocarbon dating techniques to the eye lenses of 28 females caught as by-catch. Their analysis suggests an average lifespan of at least 272 years. The two largest sharks in this study, at 493 cm and 502 cm in length, were estimated to be roughly 335 and 392 years old, respectively. What's more, since previous reports suggest that females of this species reach sexual maturity at lengths greater than 400 cm, the corresponding age would be at least 156 years old, the authors say. Based on these results, the Greenland shark is now the oldest-known vertebrate to roam the Earth.