Ancient Fish Downsized But Still Largest Ever

Once thought to be 90 feet long, the fish is now a more modest 26 to 55 feet

Of all the fish to ever swim in the seas, Leedsichthys problematicus may be the record-holder for the world's largest. But as the Jurassic plankton-feeder's species name suggests, Leedsichthys is a problematic fish.

Working with bits and pieces of incomplete skeletons, scientists have had a hard time figuring out the precise dimensions of the enormous creature. Now it seems that Leedsichthys, which swam the seas 165 million years ago, may have been smaller than previously believed-roughly half as big as earlier estimates, in fact.

Even so, it was probably a little bigger than today's plankton-feeding whale sharks, and its standing as the biggest bony fish ever is still intact.

The new evidence about the enormous fish is part of a study presented by University of Bristol paleontologist Jeff Liston this week at the 61st annualSymposium on Vertebrate Palaeontology and Comparative Anatomy in Edinburgh, Scotland.

Ever since Leedsichthys was first described by the British paleontologist Arthur Smith Woodward in 1889, researchers have understood that it was gigantic. The proportions of partial fossil remains made that clear-the bony gill rakers thatLeedsichthys used to strain plankton from the water were about three inches long, over three times the size of those found in skipjack tuna, for instance. The gill rakers were so big, in fact, that they have sometimes been confused as the bones of other prehistoric animals, such as the jaw of a leathery-winged pterosaur.