 It is now believed that "S. lessoniana" is a cryptic species complex.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.