The plesiosaurus, P. dolichodeirus, is an extinct [1] marine animal that grew to about 15 feet long. They had a small head, long neck, two pairs of paddle type flippers and a tail. Plesiosauruses are thought to have been very fast in the water catching their prey with sharp curved teeth. They had two nostrils located closer to their eyes than to the tip of their snout. [2] It is speculated that they could not breathe underwater but needed to go to the surface periodically to breathe. [3] There is some disagreement as to whether their necks with approximately 40 vertebrae [4] were very flexible. 

There has been a long running debate whether a plesiosaurus could crawl up onto land to lay eggs; their paddles (flippers) are thought to be far too weak to move their large heavy bodies out of the water. Recently, a plesiosaur, Polycotylus latippinus, fossil discovered on a ranch in Kansas was found to have a juvenile plesiosaur fossil inside suggesting live birth in water. [5]

Until recently, the external appearance of plesiosauruses was assumed to be smooth. Smooth skin would reduce the drag. Recent analysis of soft tissue from a 11.5-foot plesiosaurus (designated MH 7) has revealed triangular scales on the flippers and smooth skin on the tail. [6][7]

Plesiosaurus fossils have been found on every continent with the earliest complete skeleton found in England around 1823.  

________________________

[1] Presumed extinct

[2] Plesiosaurus, Wikipedia, viewed May 21, 2015, http://en.wikipedia.org/wiki/Plesiosaurus

[3] Plesiosaurus Dinosaur, viewed May 21, 2015, http://someinterestingfacts.net/plesiosaurus-dinosaur/

[4] Ibid., Plesiosaurus, Wikipedia

[5] Carpenter, Jennifer, Fossil’ suggests plesiosaurs did not lay eggs, Science and Environment, BBC News, August 12, 2011, http://www.bbc.com/news/science-environment-14447187

[6] Paul, A, "Paleontologists solve decades' old mystery about plesiosaur skin texture," Popular Science, February 6, 2025, internet

[7] Dixit, M, "183 million-year-old plesiosaur fossil found preserved with skin, scales," Interesting Engineering, viewed Internet March 2025

Copyright 2015, 2025   All rights reserved

.