The findings about Leedsichthys, a huge, bony, plankton-eating fish, reveal an important missing piece in the evolutionary story of fish, mammals and ocean ecosystems, a release from the University of Glasgow said Monday.
Just as dinosaurs on land evolved to created animals of huge dimensions, sea creatures also started to grow to vast proportions in the Jurassic era, they said.
"The process is known as gigantism," Jeff Liston of the National Museums of Scotland said. "It was known about in land animals at the time but we had no way of knowing if a parallel process occurred in the oceans. We now know that it did -- though the reason for appearance of these gigantic beasts, both on land and in the water, is not clear at present."
"The giant plankton-feeders we know to live in today's oceans are among the largest living vertebrate animals alive," he said. "The Leedsichthys was the first animal known to occupy this role.
"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."
Leedsichthys met the same fate as it huge land-dwelling counterparts, the researchers said, and were eventually wiped out by the same catastrophe that killed the dinosaurs 66 million years ago.