More than 160 million years ago, even as dinosaurs were roaming Earth, a massive plankton-trawling fish known as Leedsichthys problematicus swam its oceans. Scientists, who have known of the fish’s existence since the late 19th century, could only guess at its size due to the poor quality of the fossil specimens that survived. But now, after the discovery of a nearly complete skeleton buried in a quarry near Peterborough, England, a Scottish and Canadian team of researchers has confirmed this week that the Leedsichthys was nearly twice the size scientists had previously believed, and could grow to a whopping 55 feet in length.
The journey to this week’s revelations actually began with a chance discovery several years ago. Two geology students were working on a project at the quarry outside Whittlesea when they spotted fragments of bone sticking out of the rocks. When a team led by Professor Jeff Liston of the National Museums of Scotland unearthed the remains, it turned out to be a nearly complete skeleton of Leedsichthys problematicus, which lived during the Jurassic era, more than 160 million years ago.
The Victorian-era British collector Alfred Leeds was the first to discover bones of the giant fish back in 1889, near Peterborough, England. Similar discoveries were later made at sites ranging from continental Europe (northern Germany and Normandy) to Latin America (Mexico and Chile’s Atacama desert). Unfortunately, the Leedsichthys specimens that were found were usually of poor quality, as the prehistoric fish had a cartilage-heavy skeleton that does not fossilize easily. Based on their best estimates, scientists believed it could grow to more than 25 feet long, but the difficulties they faced in understanding its scale and features led to the attribution of its second name, problematicus.
After examining the skeleton found in the Whittlesea quarry along with the specimens found at various other sites, the team of researchers (including experts from Glasgow and Edinburgh Universities and the Royal Tyrrell Museum in Alberta, Canada) concluded that the fish were widely distributed throughout the world’s oceans. They believe that a 20-year-old Leedsichthys could have grown to about nine meters long, while one that lived to 38 years old could have reached a total length of 16.5 meters (or 54 feet). Such measurements means it would far outstrip the previous title-holder for world’s largest fish, the still-living whale shark (Rhincodon typus), which populate the world’s tropical seas and top out around 40 feet, or 12 meters.
According to Liston, who is scheduled to present details of his team’s findings at the Symposium on Vertebrate Palaeontology and Comparative Anatomy in Edinburgh this week, this new discovery will help scientists gain a broader understanding of the long-mysterious process known as gigantism. It’s already well known that land animals were growing much, much larger during the Jurassic era, as evidenced by the existence of such enormous dinosaurs as Apatosaurus, Diplodocus and Brachiosaurus. The fact that Leedsichthys grew so large now points to a “parallel process” taking place in the oceans around the same time.
Though the reason for this gigantism is still unknown, the team’s findings point to some major change in ocean chemistry that created an explosion in the plankton populations of Jurassic-era seas. This increase allowed suspension-feeding fish like the Leedsichthys to attain and sustain colossal sizes, dwarfing previous specimens with a similar diet.
Scientists believe Leedsichthys problematicus became extinct some 66 million years ago, after falling victim to whatever catastrophic event killed the dinosaurs. Its existence paved the evolutionary way for the giant sea mammals of today, like blue whales, as well as cartilaginous fish such as manta rays, basking sharks and whale sharks.