A prehistoric fish measuring over 54ft is the biggest ever to roam the oceans, say scientists.
The Leedsichthys lived over 10 million years ago, alongside dinosaurs in the Jurassic period, according to experts.
Despite its size, it only ate plankton, which it captured in a honeycomb mesh in its gills, trapping food as seawater passed through its mouth.
This unique system is unlike any feeding method used by fishes today.
The vast size of the dinosaur fish has only recently been confirmed because of incomplete remains of the Leedsichthys recently discovered.
Minimal skeletal remains were uncovered off the coasts of France and Mexico, but bad preservation hampered its analysis.
Also, the fish had a skeleton mostly made of cartilage and does not fossilise easily.
However, fossils of a new specimen were found in Peterborough, Cambridgeshire.
An accidental discovery in a quarry outside Whittlesea near Peterborough several years ago unearthed an almost complete skeleton of a Leedsichthys.
"Two students were working on a geology project in the quarry when they noticed pieces of bone sticking out of the rocks," said Professor Liston, who is presenting details of his team's discovery at the Symposium on Vertebrate Palaeontology and Comparative Anatomy in Edinburgh.
"It turned out to be fossil pieces of Leedsichthys - a real breakthrough."
He continued: "The giant plankton-feeders we know to live in today's oceans are among the largest living vertebrate animals alive. The Leedsichthys was the first animal known to represent this species.
"What we have demonstrated here is that a small adult Leedsichthys of eight or nine metres could reach that length within around 20 years, whereas after 38 years it would be around 16.5 metres long - possibly even outgrowing today's massive whale sharks.
"This fish was a pioneer for the ecological niche filled today by mammals, like blue whales, and cartilaginous fish, such as manta rays, basking sharks and whale sharks.
"The existence of these large suspension-feeding fish at this time is highly significant, as it would seem to be clear evidence of a major change in plankton populations in Earth's oceans of Jurassic Earth."
It is believed that the Leedsichthys was eventually wiped out by the same catastrophe that killed the dinosaurs 66 million years ago.