The discovery of this genus forms one of the most important additions that geology has made to comparative anatomy. Baron Cuvier deemed “its structure to have been the most singular, and its characters the most monstrous, that had been yet discovered amid the ruins of a former world.” To the head of a lizard it united the teeth of a crocodile, a neck of enormous length, resembling the body of a serpent, a trunk and tail having the proportions of an ordinary quadruped, the ribs of a chameleon, and the paddles of a whale. “Such,” writes Dr. Buckland, “are the strange combinations of form and structure in the Plesiosaurus, a genus, the remains of which, after interment for thousands of years amidst the wreck of millions of extinct inhabitants of the ancient earth, are at length recalled to light by the researches of the geologist, and submitted to our examination, in nearly as perfect a state as the bones of species that are now existing upon the earth.” (Op. cit., vol. v. p. 203).
The first remains of this animal were discovered in the lias of Lyme Regis, about the year 1823, and formed the subject of the paper by the Rev. Mr. Conybeare (now Dean of Llandaff), and Mr. (now Sir Henry) De la Beche, in which the genus was established and named Plesiosaurus (from the Greek words, plesios and sauros, signifying “near” or “allied to,” and “lizard”), because the authors saw that it was more nearly allied to the lizard than was the Ichthyosaurus from the same formation.
The entire and undisturbed skeletons of several individuals, of different species, have since been discovered, fully confirming the sagacious restorations by the original discoverers of the Plesiosaurus. Of these species three have been selected as the subjects of Mr. Waterhouse Hawkins’s reconstructions and representations of the living form of the strange reptiles.
No. 15.—Plesiosaurus macrocephalus.
The first of these has been called, from the relatively larger size of the head, the Plesiosaurus macrocephalus (No. 15), (Gr. macros, long, cephale, head). The entire length of the animal, as indicated by the largest remains, and as given in the restoration, is eighteen feet, the length of the head being two feet, that of the neck six feet; the greatest girth of the body yields seven feet.
No. 15. Plesiosaurus macrocephalus.
Although Baron Cuvier and Dr. Buckland both rightly allude to the resemblance of the fins or paddles of the Plesiosaur to those of the whale, yet this most remarkable difference must be borne in mind, that, whereas the whale tribe have never more than one pair of fins, the Plesiosaurs have always two pairs, answering to the fore and hind limbs of land quadrupeds; and the fore-pair of fins, corresponding to those in the whale, differed by being more firmly articulated, through the medium of collar-bones (clavicles), and of two other very broad and strong bones (called coracoids), to the trunk (thorax), whereby they were the better enabled to move the animal upon dry land.
Remains of the Plesiosaurus macrocephalus have been discovered in the lias of Lyme Regis, in Dorsetshire, and of Weston, in Somersetshire.