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Rulers Of The Ancient Seas: Plesiosaur

Each had peculiarities of its, or rather their own, for while it is convenient to speak of Ichthyosaur and Plesiosaur, there were many species of assorted sizes. The Ichthyosaurs, especially the smaller kinds, were, so to speak, reptilian porpoises, far more so than was imagined, provided, however, with four useful paddles instead of two, in addition to a powerful tail whose shape and use were long unsolved problems. The great majority of the specimens discovered had the last section of the long tail bent at an angle to the rest of the backbone and this was interpreted as indicating the existence of a flattened tail, something like that of a newt or salamander, that "flopped" over in the dead animal, twisting the hinder portion of the tail to one side. And so for many years the Ichthyosaurus was figured with a compressed tail. But when, later on, a finely preserved specimen came to light, lying upon one side and having the tail in place, lo it was much like the tail of a shark, only reversed, the lower lobe being longer than the upper. The meaning of this is that the reptile wished to come to the surface now and then to breathe while the shark goes down in search of food, or to escape from danger. One feature shown in the more perfect specimens was quite unsuspected, and that was the existence of a high back fin precisely like that of a porpoise.

Buckland described the Plesiosaur as "a snake, threaded through the body of a turtle" and this will serve pretty well for the long-necked species, even though the "shell," or carapace, of the turtle is lacking, the body of the long-necked sea reptile apparently having been covered with smooth skin. Whether or not the snake-like neck had any of the mobility of a serpent is a matter still in dispute, but we would remind those who claim that on account of their biconcave vertebræ the Plesiosaurs must have been a stiff-necked generation, that animals frequently do things that are theoretically impossible.¹ On the other hand, it is doubtful if any of them could tie their necks into knots as Cope allowed Elasmosaurus to be depicted.