Leedsichthys problematicus was a giant pachycormid (an extinct group of bony fish) that lived in the oceans of the Middle Jurassic period (Liston, 2004). Unfortunately, although fossils have been found, no one has ever found a complete spine, so its exact size is uncertain. Older estimates have ranged from 18–30 m (60–100 ft) long, with more recent ones suggesting it would have grown to around 16–22 m (54–72 ft) long making it the largest fish to have ever existed. However, the most recent estimate places it at roughly 9 m long . Its closest living relative is the bowfin.