[Animals] 25 of the strangest ancient sea monsters

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From the creepiest Cambrian critters to massive marine reptiles, wonderfully weird sea creatures have inhabited our oceans for over half a billion years. We've put together a list of 25 of the strangest ancient sea monsters ever to have lived, all of which went extinct long before humans came along.

The only reason we know that these evolutionary marvels existed is because some left behind fossilized remains in rocks. Modern researchers are still interpreting these fossils and making fresh discoveries all the time, so be sure to keep up with the latest Live Science fossil news.

Plesiosaurs were a group of marine reptiles with boat-like bodies and four flippers. There were long-necked plesiosaurs (think ancient Loch Ness monster) and short-necked plesiosaurs (imagine a Loch Ness monster with a short neck and a massive head). Plesiosaurs lived from the Triassic period (251.9 million to 201.4 million years ago) until they went extinct alongside the non-avian dinosaurs at the end of the Cretaceous period (145 million to 66 million years ago). They lived across the world's oceans. 

"Not only were these animals odd compared to things that we have alive today, but they were also globally distributed and very, very diverse," Michael Caldwell(opens in new tab), a vertebrate paleontologist at the University of Alberta in Canada, told Live Science.  

https://www.livescience.com/strangest-ancient-sea-monsters