The first fossils occur in the Upper Triassic, and the group continues until the K/T extinction event at the end of the Cretaceous (220 to 65.5 million years ago). Pterosaurs are the earliest vertebrates known to have evolved powered flight. Their wings were made from a flap of skin between their bodies and a big fourth finger (sometimes called the "wing finger"). The pterosaurs fall into two groups. The earlier Rhamphorhynchoids (e.g. "Rhamphorhynchus") had long tails and toothed jaws; The pterodactyloids (e.g. "Pterodactylus") had short tails, and many had beaks with no teeth.