The earliest vertebrates with limbs and digits—tetrapods—had descendants that eventually colonized the land and diversified into all the vertebrate forms seen in the subsequent history of life on Earth. Dinosaurs, birds, lizards, bats, snakes, whales, humans, frogs, and salamanders are all tetrapods. The ancestors of tetrapods first appeared during the Devonian Period, about 380–350 million years ago—a period that is also remarkable for being the Age of Fishes. Tetrapods evolved from within a group of fishes called the lobe-fins whose other descendants include the living lungfishes and the coelacanth Latimeria. Among fossil forms, the tetrapods' closest relatives are the osteoleptiforms, whose other members are now extinct. Until very recently, few fossils representing this important stage in the history of life had been found, and ideas about how the transition from fish to tetrapod happened, where it happened, and in what sequence tetrapod characteristics arose, had to rely largely on speculation. More clues have now come to light, and it is possible to put together a few pieces in the jigsaw puzzle. The emerging picture is more complicated than expected, and there are still many questions.