Leedsichthys

Leedsichthys problematicus ("leeds fish") was a giant fish of the Jurassic period. Its fossils were first found in England. 
It was a pachycormid, a group of extinct ray-finned fishes (Actinopterygii). "Leedsichthys" is the largest fish known, with an estimated length of up to 16 metres. The blue whale is twice as long, at 30 metres, but it is a mammal, not a fish.
"Leedsichthys" fossils are incomplete, making it impossible to know the exact length. The fossil is named after its discoverer, Alfred Nicholson Leeds, who discovered it before 1886 near Peterborough, England. No full fossil is known, mainly because parts of the skeleton were made of cartilage, which does not fossilise.
The front of the snout was made of cartilage.
"Leedsichthys" fossils have also been found in France, Germany and Chile.
Food.
Like the world's biggest fish today, the whale shark, "Leedsichthys" was a filter feeder, getting its nutrition from plankton. Remains of over 70 individuals have been found.