Alopias grandis is a species of giant thresher shark from the Miocene. She was the U.S. Navy's second submarine to be named after the thresher shark. The three extant thresher shark species are all in the genus "Alopias". The bigeye thresher shark is rarely encountered by divers underwater and poses no danger. Sometimes the thresher shark will slice the fish in half before eating. The thresher shark has a short head and a cone-shaped nose. In 1810, Constantine Samuel Rafinesque described "Alopias macrourus" from a thresher shark caught off Sicily. The common thresher is the largest thresher shark species, commonly reaching long and in weight.