was collected by Lesson off the coast of New Guinea during the circumnavigational voyage of the French corvette La Coquille (1822–1825) under the command of Louis Isidore Duperrey. Numerous other species of Sepioteuthis were described from the Pacific and Indian Oceans in the late 19th century and in the early 20th century. In 1939 the Belgian malacologist William Adam examined the specimens of Sepioteuthis recovered from the tropical western Pacific. He synonymised the twelve species then considered valid under Sepioteuthis lessoniana. A study in 1993 by Segawa et al. revealed that the population of S. lessoniana in Okinawa may actually be composed of three distinct species. This was confirmed in genetic studies by Izuka et al. in 1994. Triantafillos and Adams in 2005 also showed that S. lessoniana in Shark Bay, Australia is composed of two species. These findings indicate that S. lessoniana may actually comprise several very similar and closely related species. It is now believed that S. lessoniana is a cryptic species complex. Description Like other members of the genus Sepioteuthis, bigfin reef squids are easy to distinguish from other squids in that they possess thick and muscular oval fins that extend around almost the entire mantle. The fins extend about 83 to 97% of the mantle length and are 67 to 70% of the mantle length in width. Because of these fins, bigfin reef squids are sometimes mistaken for cuttlefish, a fact reflected by their scientific names. A narrow blue or white line is visible at the point of attachment of the fins to the mantle. A fleshy ridge is also present where the fins meet at the back of the squid. The mantles of bigfin reef squids are cylindrical, tapering to a blunt cone at the posterior. The mantle is usually long in males and long in females. Both sexes can reach a maximum mantle length of . Adult males weigh , while adult females are . Both sexes can attain a maximum documented weight of . The forward margin of the mantle on the ventral side is concave. Their eyes are large and covered entirely by a transparent secondary cornea. They are greenish at the base. A pair of prominent ridges (olfactory crests) are present on the ventral surface of the head at the rear edge of the eyes. The mouth area is supported by seven triangular flaps (buccal lappets), each with 0 to 7