The world of the early Jurassic would have been warmer than it is today. There has been no evidence of ice sheets anywhere on the planet, and the sea level was much higher. This was the perfect environment for Attenborosaurus to thrive.

Large parts of Europe, where Attenborosaurus dwelled, would have been underwater during the early part of the Jurassic. It was a world blanketed in warm tropical oceans and shallow seas teeming with fish, ammonites, other marine reptiles, and turtles, says Becky McKean, a geologist at St. Norbert College in De Pere, Wisconsin. 

But we’re not sure why Attenborosaurus went extinct 189 million years ago, though many similarly giant marine reptiles would come after it. Still, the species was important because it signaled an explosion of plesiosaurs that lasted for millions of years before they went extinct for good about 66 million years ago. And today, unfortunately, unless you count the Loch Ness Monster, our oceans are distinctly empty of sea monsters.

The Evolution of Attenborosaurus

Attenborosaurus lived at the beginning of the evolution of plesiosaurs — long-neck marine reptiles — when the species hadn’t reached its full enormous size. It’s also hard to know how big the species would have been unless you have all of the vertebrae. But in this case, Attenborosaurus was an almost complete specimen when it was found, and estimates for the species run at around 14 feet. 

During the Cretaceous, plesiosaurs grew longer necks and bodies and generally got much longer. Elasmosaurus, for example, which lived during the Late Cretaceous period 81 million years ago, had among the longest necks of any plesiosaur, with the entire creature extending to around 43 feet in length. With its long neck and small head, it would have been ideally shaped so that its protracted neck allowed it to reach fish long before its enormous body would scare them away.

Read More: Species of Ichthyosaur Is Largest Known Marine Reptile at 80 Feet Long

Other species that lived alongside Attenborosaurus included a narrow-nosed giant called Ichthyosaurus. The reptile resembled a dolphin but wasn’t a mammal, with a vertical, instead of a horizontal, tail fluke. Pterosaurs, the flying reptile cousin to dinosaurs, would have circled the seas overhead, occasionally diving for fish down below.

“This was a part of the world that was chalked full of life,” says McKean. 

Attenborosaurus mostly hunted fish, which researchers know from the enormous, round, and conical shape of its teeth. It might also have sampled the invertebrates that lived in the sand on the ocean floor, says Miguel Marx, a Ph.D. student in geology at Lund University in Lund, Sweden. The species would have been one of the largest marine reptiles of that time, making it unlikely that most species would have preyed on it.

With so many species in the oceans, Attenborosaurus ate what it could fit in its mouth.

“It’s likely that different plesiosaurs were eating different things because there was a lot of competition in marine environments at that time,” says Marx.

Read More: Why Were Prehistoric Marine Reptiles So Huge?

A Forgotten History

We’re extremely lucky that we’ve even ever heard of Attenborosaurus. The specimen, which was first discovered in 1880 and written about in a study the following year, almost became a remnant of history when Nazis bombed the British Museum during World War II, and the specimen was destroyed and lost to time. 

It just so happened that two casts of it had been made before it was destroyed, and since then, it’s still the only (though almost complete) specimen that’s ever been found. In recent years, Attenborosaurus, which lived in the waters off of England, was renamed for the great British naturalist Sir Richard Attenborough.

There’s also a lot we don’t know about Attenborosaurus and other plesiosaurs because unlike dinosaurs, very few people study them, says Marx. We have fossils on every continent and from every period of the Age of Dinosaurs, “we just don’t have enough researchers studying them,” he says. 

Read More: 5 of the Most Interesting Prehistoric Marine Reptiles

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Sara Novak is a science journalist based in South Carolina. In addition to writing for Discover, her work appears in Scientific American, Popular Science, New Scientist, Sierra Magazine, Astronomy Magazine, and many more. She graduated with a bachelor’s degree in Journalism from the Grady School of Journalism at the University of Georgia. She’s also a candidate for a master’s degree in science writing from Johns Hopkins University, (expected graduation 2023).