NatGeo: Shark-like Tails Sped Ancient Sea Monsters Through Oceans

A new study finds that the prehistoric predators of the ocean, mosasaurs, were not as slow as scholars once thought.

The first mosasaur tail on record with a preserved soft tissue outline (top picture). In similarity with whales and ichthyosaurs, Mosasaurs gradually attained a shark-like appearance (bottom picture) Image courtesy NatGeo.

The first mosasaur tail on record with a preserved soft tissue outline (top picture). In similarity with whales and ichthyosaurs, Mosasaurs gradually attained a shark-like appearance (bottom picture) Image courtesy NatGeo.

Science journalist Jane J. Lee with National Geographic reported on the research of SMU Research Associate Michael J. Polcyn, who co-authored a new study that found the ancient sea monsters known as mosasaurs were not as slow as paleontologists once thought, thanks to their shark-like tails.

The National Geographic article, “Shark-like Tails Sped Ancient Sea Monsters Through Oceans,” was published in September.

Polcyn is a vertebrate paleontologist and director of the Visualization Laboratory in SMU’s Roy M. Huffington Department of Earth Sciences whose current research interests include the early evolution of Mosasauroidea and adaptations in secondarily aquatic tetrapods. His research involves the application of advanced imaging techniques and other computer-based technology to problems in paleontology. Polcyn’s fieldwork is currently focused in Upper Cretaceous marine deposits of Angola.

Read the National Geographic article.


By Jane J. Lee
National Geographic

Sea monsters lying in wait for unsuspecting prey sounds scary enough. But slap on a tail that let them run down their dinner—much like today’s great white sharks—and mosasaurs could truly be considered one of the ancient world’s nightmares.

And that’s exactly what a new study published September 10 in Nature Communications has confirmed.

A 72-million-year-old fossil specimen of Prognathodon—a genus of mosasaur—found in a Jordanian quarry in 2008 revealed fin-like soft-tissue imprints along its tail. Those imprints demonstrate that this group of ancient sea monsters possessed powerful tails similar to ones seen on sharks today, rather than the puny ones on eels or sea snakes.

Mosasaurs were aquatic reptiles that prowled the seas and freshwater streams toward the end of the age of dinosaurs, about 98 to 66 million years ago.

Although they are fairly well represented in the fossil record, finding soft-tissue evidence for shark-like tails on these lizard ancestors isn’t something that study co-author Michael Polcyn, a vertebrate paleontologist at Southern Methodist University in Dallas, Texas, expected to come across in his lifetime.

This fossil is so well preserved that researchers can discern the direction of stiffening fibers in the tail, he added.

“You can [also] see the outlines of scales,” said study co-author Johan Lindgren, a vertebrate paleontologist at Lund University in Sweden.

Questioning the Past
For over 200 years, scholars thought mosasaurs sported paddle-shaped tails much like sea snakes, said Lindgren. Since mosasaurs are true lizards, scholars formerly thought that the ancient reptile’s tail should look like those on their living lizard relatives.

But this limited mosasaurs — some of which could grow to over 33 feet (10 meters) long — to short bursts of speed typical of ambush predators.

“It was generally assumed that their swimming speeds were low and at best they could do a quick lunge,” said Bruce Young, a researcher at the Kirksville College of Osteopathic Medicine in Missouri who is studying how reptiles move.

Read the National Geographic article.

SMU is a nationally ranked private university in Dallas founded 100 years ago. Today, SMU enrolls nearly 11,000 students who benefit from the academic opportunities and international reach of seven degree-granting schools. For more information see

SMU has an uplink facility located on campus for live TV, radio, or online interviews. To speak with an SMU expert or book an SMU guest in the studio, call SMU News & Communications at 214-768-7650.

This entry was posted in Earth & Climate, Fossils & Ruins, Plants & Animals, Researcher news, SMU In The News and tagged , , . Bookmark the permalink.

About Margaret Allen