Leedsichthys was a gigantic (about 53 feet or 16 metres long) bony fish that lived in the oceans during the middle Jurassic period.
Leedsichthys was a pachycormid (pachycormids are an extinct group of bony fish). Like modern large fish, whale shark and basking shark Leedsichthys was a filter feeder that ate zooplankton (tiny animals and other similar organisms that are drifting in oceans).
There is some evidence of predation on Leedsichthys by pliosaurs, but the fossil evidence also shows that Leedsichthys was able to escape the large pliosaurs even after they have wounded them.