The fossil of a giant fish discovered near Peterborough has led scientists to believe it could have been the whale of its time.
Leedsichthys lived in the Middle Jurassic period around 165 million years ago, but although a number of skeletal remains of this huge, bony fish had been uncovered over the years they hadn’t preserved well, so no one was sure how large the fish could grow.
But an almost complete skeleton of the fish was discovered at a quarry in Whittlesey, Peterborough several years ago, and now scientists have been able to use this, alongside other fragments discovered elsewhere to get some idea of the ages and sizes of the specimens.
An international team of researchers from National Museums Scotland and the Universities of Glasgow and Edinburgh have deduced that Leedsichthys could grow to eight or nine metres in 20 years and reach 16.5 metres in length in 38 years - possibly even outgrowing today’s massive whale sharks.
Scientists believe the monster fish was a suspension feeder, living on enormous quantities of plankton which it extracted from the seawater passing through it mouth using a unique mesh structure on its gills, functioning like a trawler’s net - very different to what we see in today’s suspension-feeding fish and whales.
Professor Jeff Liston, from the University of Glasgow, said: "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 occupy this role.
"What we didn't have any clear idea of, was how large this large fish really was: its skeleton preserves poorly, it is often just isolated fragments, so previous size estimates were largely historical arm-waving exercises."
"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.
"Before then, vertebrate suspension-feeders did not get larger than 50cm/20" in length. Something important had changed. 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 – a 'smoking gun' that something new, widespread and highly edible was around – possibly related to the first appearance of small crustaceans called copepods."
The findings appear in the journal Mesozoic Fishes 5: Global Diversity and Evolution - Proceedings of the International Meeting.
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