This week we’re going to find out about the biggest turtles that ever lived! Spoiler: one of them is alive right now, swimming around eating jellyfish. A green sea turtle. These guys are adorable: A hawkbill glowing like a neon sign! The majestic and enormous leatherback: Bebe leatherback. LET ME GOW Seriously, how are baby sea turtles so darn cute? Archelon was a big tortle: Further reading: This is a link to a pdf of that "Historicity of Sea Turtles Misidentified as Sea Monsters" article Show transcript: Welcome to Strange Animals Podcast. I’m your host, Kate Shaw. This week we’re back in the sea, but not the deep sea this time, because we’re looking at marine turtles! The oldest known turtle ancestor lived around 220 million years ago, but it wouldn’t have looked a whole lot like a modern turtle. For one thing, it had teeth instead of a bill. It resembled a lizard with wide ribs that protected its belly. It lived in the ocean, probably in shallow inlets and bays, but it may have also spent part of its time on land. Some researchers think it may have had at least a partial shell formed from extensions of its backbone, but that this didn’t fossilize in the three specimens we have. The oldest sea turtle fossil found so far has been dated to 120 million years old. It was seven feet long, or 2 meters, and already showed a lot of the adaptations that modern sea turtles have. Researchers think it was closely related to the green sea turtle and the hawksbill sea turtle. Seven species of sea turtle are alive today. They all have streamlined shells and flippers instead of feet. They all breathe air, but they have big lungs and can stay underwater for a long time, up to about an hour while hunting, several hours when asleep or resting. Like whales, they surface and empty their lungs, then take one huge breath. They can see well underwater but can probably only hear low-frequency sounds. Sea turtles have a special tear gland that produces tears with high salt concentration, to release excess salt from the body that comes from swallowing sea water. They migrate long distances to lay eggs, thousands of miles for some species and populations, and usually return to the same beach where they were hatched. Female sea turtles come ashore to lay their eggs in sand, but the males of most species never come ashore. The exception is the green sea turtle, which sometimes comes ashore just to bask in the sun. Once the babies hatch, they head to the sea and take off, swimming far past the continental shelf where there are fewer predators. They live around rafts of floating seaweed call sargassum, which protects them and attracts the tiny prey they eat. Six of the extant sea turtles are relatively small. Not small compared to regular turtles, small compared to the seventh living sea turtle, the leatherback. More about that one in a minute. The other six are the green, loggerhead, hawksbill, Kemp’s ridley and Olive ridley, and the flatback. Let’s start with the green sea turtle, since I just mentioned it. Its shell is not always green. It can be brown or even black depending on where it spends most of its life. Green turtles that live in colder areas of the Pacific have darker shells, which probably helps them stay warm by absorbing more heat from sunlight. Young turtles have darker shells than old turtles for the same reason. The green sea turtle can grow up to five feet long, or 1.5 meters, can live some 80 years, and mostly eats plants, especially seagrass, although babies eat small animals like worms, jellyfish, and fish eggs. A recent satellite tracking study of green sea turtles in the Indian Ocean tracked the turtles to a huge underwater seagrass meadow that no human realized existed until then. The meadows were farther underwater than the ones researchers knew about, up to 95 feet deep, or 29 meters. Researchers think the seagrass can grow at these depths because ...