Old, older, Greenland shark

The Greenland shark, also known as the grey shark, is a curious animal: the torpedo-shaped cartilaginous fish grows to be more than five meters (around 16.4 feet) long on average and weighs up to 2.5 tons. But it makes its way through the cold waters of the North Atlantic at the incredibly slow top speed of just 2.6 kilometers per hour.

This economical propulsion strategy may be a reason for the animal's extraordinary longevity. They live longer than any other vertebrate, according to a study by an international group of researchers from the University of Copenhagen. They published their findings in the current issue of the journal Science.

The researchers examined 28 female sharks that were caught during several expeditions. The average age of the animals was 272 years old. However, the largest one was considerably older: a whopping 392 years. This figure is based on radiocarbon dating and may not be 100 percent accurate but it still surprised the scientists. Not as much as the late sexual maturity of the sharks though. Because they cannot procreate until they reach a length of 4 meters, and yet they grow very slowly, it takes about 150 years, according to the study, until the Greenland sharks can look forward to offspring.

That is a huge problem because the animals often land in fishing nets as by-catch. If too many of them are caught and not enough new Greenland sharks are born in time, it could spell doom for the species.

The International Union for Conservation of Nature (IUCN) currently rates the Greenland shark as "near threatened."

Fun Fact:
Apparently, Greenland sharks feed primarily on sleeping seals and fish.