6 Amazing Mosasaur Facts to Prepare You For Jurassic World

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Meet Mosasaurus, a gigantic carnivore that swam seas around the globe 80 million to 66 million years ago. On June 12, you can see one doing its best Shamu impression in Jurassic World.

Few people on earth know more about the amazing mosasaur family than Michael J. Everhart, who’s been collecting marine fossils for decades. A celebrated paleontologist, he serves as an adjunct curator at the Sternberg Museum of Natural History in Hays, Kans. Between digs, Everhart manages Oceans of Kansas, which spawned a companion book in 2005. Everhart recently spoke to mental_floss about key mosasaur characteristics.

1. The Biggest Mosasaurs Were Longer Than T. rex.

Though we haven’t yet found any complete specimens, Everhart argues that both Mosasaurus and Tylosaurus (a North American cousin) probably “reached lengths of 14 to 15 meters,” or about 46–50 feet. Though Tyrannosaurus was much heavier, it maxed out at around 40 feet from nose to tail. At 60 feet long, the captive in Jurassic World surpasses even the wildest mosasaur size estimates.

Not all mosasaurs were giants. In real life, some species would have looked dwarfish beside an average American alligator. Fully grown Carinodens belgicus, for example, were likely a mere 6.5 feet long.

2. Mosasaur Jaws Are Pretty Interesting/Terrifying.

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Look closely at this Jurassic World poster and you’ll see a Mosasaurus complete with two extra rows of teeth inside its maw. Did some Hollywood concept artist make these up to help the thing look scarier? Actually, no. Gripping food underwater would have been a challenge for mosasaurs. Luckily, like present-day snakes, they had a toothy secret weapon: pterygoid ("flanged") teeth, which were anchored to bones in the roof of the mouth. These made the job of handling—and swallowing—prey a whole lot easier. But, as Everhart points out, mosasaur teeth “were embedded in the fleshy tissue of their gums... [and] not nearly as visible as portrayed” in the movie.

3. Snakes and Monitor Lizards Are Their Closest Living Relatives.

Like their mosasaur relatives, snakes have extra teeth. The extinct reptiles were also closely akin to monitor lizards such as the Komodo dragon. Perhaps mosasaurs had forked, flickering tongues like their modern brethren. Unfortunately, because soft tissues seldom fossilize, we may never know for sure.

4. Mosasaurs Gave Birth to Live Young.

Everhart estimates that a 50-foot mosasaur would have weighed around 5000 kg (5.5 tons). Something that big would have really struggled to pull itself ashore to give birth. So like many oceanic animals, it gave birth beneath the waves.

We know this thanks to a Plioplatecarpus specimen. The midsize animal was found in both hemispheres' oceans from 83 to 71 million years ago. The “mother mosasaur,” which was discovered in South Dakota, shed some light on how these creatures came into the world: Scattered around the gravid (or pregnant) reptile’s body were the remains of her unborn young.

5. Just Before Dying Off, the Mosasaur Family Really Diversified.


Mosasaurs were wildly successful. Their fossils have been found on every continent, even Antarctica. And during the last 25 million years of the family’s existence, strange new varieties began to emerge. While more traditional mosasaurs dined on fish, squids, and smaller reptiles in the open ocean, a few latecomers carved out vastly different niches. Consider Globidens, which evolved rounded teeth designed for crushing hard shells. Later, the heavily built Goronyosaurus (whose skull almost looks like it was stolen from some poor crocodile) invaded African rivers. And then there is the narrow-snouted Plotosaurus with its weird, fish-like build—the potential hallmark of a streamlined, high-speed lifestyle.

6. Jurassic World takes liberties with its Mosasaurus.

For starters, Ingen’s Mosasaurus seems awfully acrobatic. “It’s not a killer whale,” Everhart says. This “tail-wagging” creature, he explains, simply wasn’t “fast enough in the water to do the kinds of jumps that are shown in the movie.” Also, the oversized specimen would probably surpass 6 tons in weight. “[That] is a lot of mass to try to shoot straight up out of a relatively small and shallow captivity pool,” Everhart says.

Everhart also takes issue with how the trailer released on April 20 portrays Mosasaurus flippers in action. “Their paddles would be held tightly against the body while swimming—watch a crocodile swim—not fluttering around creating drag,” he says. Theoretically, the appendages were used to help stabilize the animal. But the film shows them actively propelling it forward.

One other inaccuracy: The beast’s rough, croc-like hide. Real mosasaurs were relatively smooth skinned and covered with tiny scales, Everhart says.

Still, such exaggerations are par for the course. Whenever Hollywood tries to put prehistoric life on the silver screen, tweaks are always made to ensure the creatures are as cinematic and entertaining as possible. At the very least, Jurassic World already has people buzzing about mosasaurs, a group that deserves way more time in the spotlight.