the tail region itself consists of the caudal peduncle and the caudal fin. the caudal peduncle sometimes has notches known as "precaudal pits", which are found just ahead of the caudal fin. the peduncle may also be horizontally flattened into lateral keels. the caudal fin has both, an upper lobe, and a lower lobe, that can be of different sizes and the shape depends of which species the shark is.