Recently discovered fossils of Leedsichthys – the biggest fish that ever swam in oceans – show that the prehistoric creature could grow to 26 – 30 feet (8-9 m) in two decades and reach 54 feet (16.5 m) in length in 38 years. Leedsichtys problematicus (Dmitry Bogdanov / CC BY 3.0). Leedsichthys was a huge bony, plankton-eating fish that lived in the Middle Jurassic period around 165 million years ago. A number of skeletal remains of the creature...