These giant sea reptiles lived in freshwater rivers, too (earthsky.org)

[eppur_se_muova]

Posted by
Shireen Gonzaga
December 18, 2025

Chemical analysis of a mosasaur tooth reveals a surprise

Mosasaurs were giant aquatic reptiles that lived 94 to 66 million years ago. While T. rex was the dominant predator on land, mosasaurs were the apex predators of the sea. But scientists from Uppsala University in Sweden said on December 12, 2025, that they have new evidence showing mosasaurs also lived in freshwater, in inland rivers. Their diverse habitats suggest they were adapting to a changing environment.

In 2022, researchers found a mosasaur tooth at an unexpected location in North Dakota. They recovered it from ancient river deposits alongside a T. rex tooth and the jawbone of a freshwater crocodile-like (or crocodilian) reptile. Plus, the area was known for its fossilized Edmontosaurus duck-billed dinosaurs.

How did a seagoing mosasaur’s tooth end up in a freshwater river?

In this new study, scientists found answers in the mosasaur’s tooth enamel. A chemical analysis of certain elements revealed that this mosasaur had, in fact, lived in freshwater, not salt water.

The researchers published their study in the peer-reviewed journal BMC Zoology on December 12, 2025.
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more: https://earthsky.org/earth/giant-sea-reptiles-mosasaurs-freshwater-predators/?mc_cid=8062ada9aa

[rampartd]

1. freshwater rivers? maybe loch ness or lake champlain?

66 million years ago was the Chicxulub event, if any dinosaur survived, why not the aquatic ones?

[Dave Bowman]

5. I don't think so.

[czarjak]

2. All that fancy lernin's gonna piss somebody off!

[littlemissmartypants]

3. Thank you. ❤️

[Inkey]

4. Their 28 million year reign of the waterways allowed them

to exist in both fresh and salt water. Seeking food, breeding, and climate diversity, are the hallmarks of evolving adaptations.