What is a Pliosaur?

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  • Written By: Michael Anissimov
  • Edited By: Bronwyn Harris
  • Last Modified Date: 13 September 2019
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Pliosaurs (Greek for: "sailing lizards" or "fin lizards") were a suborder of marine reptiles that lived during the Jurassic and Cretaceous periods, from about 200 million years ago (Thalassiodracon) to about 85 million years ago, when they died out. Ranging in length from 4 to 15 meters (13-50 ft), pliosaurs were carnivores that mostly ate fish, but probably also ichthyosaurs and other plesiosaurs. The pliosaurs are one of two suborders of order Plesiosauria, alongside their close relatives, the better-known plesiosaurs.

Pliosaurs were slender animals, but stockier than their relatives the plesiosaurs, and had short necks. Instead of long necks and short heads, like plesiosaurs, the pliosaur had a long head and short neck, more like a crocodile. The largest pliosaurs had heads 2 m (6.5 ft) long. Unlike some plesiosaurs, which mostly kept to small fish, pliosaurs seem highly adapted for large prey. With a 10 ft (3 m) jaw and teeth the size of cucumbers, the largest pliosaurs could have swallowed a cow — or several humans — in a single bite.


Some two dozen species of pliosaur fossils have been dug up, with notable samples located in China, Argentina, England, Alaska, and Antarctica. A complete pliosaur skeleton was not found until an Antarctic dig in 2006. Parts of an earlier skeleton found by the same Oslo team, dubbed "The Monster" or "the T. rex of the Seas," is among the largest marine reptiles yet found, with a length of 15.25 m (50 ft). Although it is mistakenly called the largest marine reptile yet found, it is exceeded in size by members of several mosasaur lineages, including Mosasaurus hoffmanni and Hainosaurus bernardi (17 m/55 ft), and a species of plesiosaur found in Mexico nicknamed the Monster of "Aramberri" (around 15 m long). The Aramberri find was initially incorrectly identified as a pliosaur, and the size was exaggerated to 18 m or larger.

Some well-known examples of pliosaur genera include Pliosaurus, Peloneustes, Macroplata, Kronosaurus, Pliosaurus, Peloneustes, and Liopleurodon. Pliosaurs were evidently global or near-global in their distribution. The time when pliosaurs lived in the ocean alongside plesiosaurs, ichthyosaurs, sharks, and mosasaurs are sometimes called the most dangerous seas in the history of life.


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Post 4

@croydon - Considering the stories of monsters from the deep that were once popular among sailors, I don't think it would have stopped humanity from getting into the water, even if pliosaurs were a danger.

Even the largest pliosaur wasn't as big as the larger whales and people hunted them in little canoes.

Post 3

@umbra21 - Well, there's no guarantee that it would have wanted to eat people. I mean, sperm whales are predators that live off large prey and could, in theory, eat a human, but as far as I know there's no recorded incidence of them doing so (aside from Jonah, of course). Even Orcas, who are quite vicious predators and will definitely eat mammals have never been recorded hunting humans in the wild.

And sharks might be dangerous, but even they would much rather have a fish or a seal. Most attacks are supposedly them mistaking a swimming for one of those.

So it might be possible that pliosaurs wouldn't have wanted anything to do with humans and we could have co-existed quite easily.

Post 2

We are so lucky that all the massive predators that used to roam the oceans have died out by now. I've seen recreations of a pliosaur in a museum and nothing really prepares you for the reality of such a massive creature. I doubt humanity would have ever become a sea-faring race with animals like that to contend with in early boats.

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