Tetrapods (from tetra = “four”, and pous = “foot”) include amphibians, reptiles (including dinosaurs), birds, and mammals. The first well-documented tetrapod remains are known from the latest Devonian (about 360 million years ago) although tracks belonging to this group are known from rocks that are 395 million years old. Scientists agree that tetrapods evolved from a group called the lobe-finned fishes. Fins turned into legs even before the first tetrapods moved onto land. Lobe-finned fishes developed the first lungs, allowing them to breathe air. The first tetrapods still had both gills and lungs, suggesting a gradual transition from breathing under water to air-breathing. The move to land also required a stronger backbone to support the body while walking. Among present-day animals, lungfishes are the closest living relatives of tetrapods.