Part 18 (1/2)

These strange and gigantic Saurians seem almost to disappear during the succeeding geological periods; for, although they have been discovered as low down as the Trias in Germany, and as high up as the Chalk in England, they only appear as stragglers in these epochs; so, too, the Reptiles, the existing Saurians are, as it were, only the shadowy, feeble representatives of these powerful races of the ancient world.

Confining ourselves to well-established facts, we shall consider in some detail the best known of these fossil reptiles--the _Ichthyosaurus_, _Plesiosaurus_, and _Pterodactyle_.

The extraordinary creature which bears the name of _Ichthyosaurus_ (from the Greek words ????? sa????, signifying fish-lizard), presents certain dispositions and organic arrangements which are met with dispersed in certain cla.s.ses of animals now living, but they never seem to be again reunited in any single individual. It possesses, as Cuvier says, the snout of a dolphin, the head of a lizard, the jaws and teeth of a crocodile, the vertebrae of a fish, the head and sternum of a lizard, the paddles like those of a whale, and the trunk and tail of a quadruped.

Bayle appears to have furnished the best idea of the Ichthyosaurus by describing it as the Whale of the Saurians--the Cetacean of the primitive seas. It was, in fact, an animal exclusively marine; which, on sh.o.r.e, would rest motionless like an inert ma.s.s. Its whale-like paddles, and fish-like vertebrae, the length of the tail and other parts of its structure, prove that its habits were aquatic; as the remains of fishes and reptiles, and the form of its teeth, show that it was carnivorous.

Like the Whale, also, the Ichthyosaurus breathed atmospheric air; so that it was under the necessity of coming frequently to the surface of the water, like that inhabitant of the deep. We can even believe, with Bayle, that it was provided, like the Whale, with vents or blowers, through which it ejected, in columns into the air, the water it had swallowed.

The dimensions of the Ichthyosaurus varied with the species, of which five are known and described. These are _Ichthyosaurus communis_, _I.

platydon_, _I. intermedius_, _I. tenuirostris_, and _I. Cuvierii_, the largest being more than thirty feet in length.

[Ill.u.s.tration: Fig. 96.--Ichthyosaurus platydon.]

[Ill.u.s.tration: Fig. 97.--Lower jaw of Ichthyosaurus. (Dr. Buckland.)]

[Ill.u.s.tration: Fig. 98.--Skeleton of Ichthyosaurus.

Containing teeth and bones of Fishes in a coprolitic form. One-fifteenth natural size.]

The short, thick neck of the Ichthyosaurus supported a capacious head, and was continued backwards, from behind the eyes, in a column composed of more than a hundred vertebrae. The animal being adapted, like the whale, for rapid movement through the water, its vertebrae had none of the invariable solidity of those of the Lizard or Crocodile, but rather the structure and lightness of those of Fishes. The section of these vertebrae presents two hollow cones, connected only by their summits to the centre of the vertebrae, which would permit of the utmost flexibility of movement. The ribs extended along the entire length of the vertebral column, from the head to the pelvis. The bones of the sternum, or that part of the frame which supported the paddles, present the same combinations with those of the sternum in the Ornithorhynchus, or Duck-billed Platypus, of New Holland, an animal which presents the singular combination of a mammalian furred quadruped having the bill of a duck and webbed feet; which dived to the bottom of the water in search of its food, and returned to the surface to breathe the air. In this phenomenon of living Nature the Creator seems to have repeated, in our days, the organic arrangements which he had originally provided for the Ichthyosaurus.

In order that the animal should be able to move with rapidity in the water, both its anterior and posterior members were converted into fins or paddles. The anterior fins were half as large again as the posterior.

In some species each paddle was made up of nearly a hundred bones, of polygonal form, and disposed in series representing the phalanges of the fingers. This hand, jointed at the arm, bears resemblance, in osteological construction, to the paddles, without distinct fingers, of the Porpoise and the Whale. A specimen of the posterior fin of _I.

communis_, discovered at Barrow-on-Soar, in Leicesters.h.i.+re, in 1840, by Sir Philip Egerton, exhibited on its posterior margin the remains of cartilaginous rays, which bifurcated as they approached the edge, like those in the fins of a fish. ”It had previously been supposed,” says Professor Owen, ”that the locomotive organs were enveloped, while living, in a smooth integument, like that of the turtle and porpoise, which has no other support than is afforded by the bones and ligaments within; but it now appears that the fin was much larger, expanding far beyond the osseous frame-work, and deviating widely in its fish-like rays from the ordinary reptilian type.” The Professor believes that, besides the fore-paddles, these stiff-necked Saurians were furnished at the end of the tail with a fin to a.s.sist them in turning, not placed horizontally, as in the whale, but vertically, forming a powerful instrument of progression and motion. It is obvious that the Ichthyosaurus was an animal powerfully armed for offence and defence. We cannot say, with certainty, whether the skin was smooth, like that of the whale or lizard, or covered with scales, like the great reptiles of our own age. Nevertheless, as the scales of the Fishes and the cuira.s.s and h.o.r.n.y armour of other Reptiles of the Lias are preserved, and as no such defensive scales have been found belonging to the Ichthyosaurus, it is probable that the skin was naked and smooth. The tail, composed of from eighty to eighty-five vertebrae, was provided with large and long paddles, arranged vertically as in the Whale.

It is curious to see to what a degree of perfection has been carried, in our days, the knowledge of the antediluvian animals, their habits, and their economy. Fig. 98 represents the skeleton of an Ichthyosaurus found in the Lias of Lyme Regis, which still retains in its abdominal cavity coprolites, that is to say, the residue of digestion. The soft parts of the intestinal ca.n.a.l have disappeared, but the _faeces_ themselves are preserved, and their examination informs us as to the alimentary regimen of this animal which has perished from the earth many thousands, perhaps millions, of years. Mary Anning, to whom we owe many of the discoveries made in the neighbourhood of Lyme Regis, her native place, had in her collection an enormous coprolite of the Ichthyosaurus. This coprolite (Fig. 99) contained some bones and scales of Fishes, and of divers Reptiles, well enough preserved to have their species identified.

It only remains to be added that, among the bones, those of the Ichthyosaurus were often found, especially those of young individuals.

The presence of the undigested remains of vertebrae and other bones of animals of its own species in the coprolites of the Ichthyosaurus proves, as we have already had occasion to remark, that this great Saurian must have been a most voracious monster, since it habitually devoured not only fish, but individuals of its own race--the smaller becoming the prey of the larger. The structure of the jaw of the Ichthyosaurus leads us to believe that the animal swallowed its prey without dividing it. Its stomach and intestines must, then, have formed a sort of pouch of great volume, filling entirely the abdominal cavity, and corresponding in extent to the great development of the teeth and jaws.

[Ill.u.s.tration: Fig. 99.--Coprolite, enclosing bones of small Ichthyosaurus.]

[Ill.u.s.tration: Fig. 100.--Coprolite of Ichthyosaurus.]

The perfection with which its contents have been preserved in the fossilised coprolites, furnishes indirect proofs that the intestinal ca.n.a.l of the Ichthyosaurus resembled closely that of the shark and the dog-fish--fishes essentially voracious and destructive, which have the intestinal ca.n.a.l spirally convoluted, an arrangement which is exactly that indicated in some of the coprolites of the Ichthyosaurus, as is evident from the impressions which the folds of the intestine have left on the coprolite, of which Fig. 100 is a representation. In the cliffs near Lyme Regis coprolites are abundant in the Lia.s.sic formation, and have been found disseminated through the shales and limestones along many miles of that coast.

What an admirable privilege of science, which is able, by an examination of the simplest parts in the organisation of beings which lived ages ago, to give to our minds such solid teachings and such true enjoyments!

”When we discover,” says Dr. Buckland, ”in the body of an Ichthyosaurus the food which it has engulfed an instant before its death, when the intervals between its sides present themselves still filled with the remains of fishes which it had swallowed some ten thousand years ago, or a time even twice as great, all these immense intervals vanish, time disappears, and we find ourselves, so to speak, thrown into immediate contact with events which took place in epochs immeasurably distant, as if we occupied ourselves with the affairs of the previous day.”

[Ill.u.s.tration: Fig. 101.--Skull of Plesiosaurus restored. (Conybeare.)

_a_, profile; _b_, seen from above.]

The name of _Plesiosaurus_ (from the Greek words p??s???, _near_, and sa????, _lizard_) reminds us that this animal, though presenting many peculiarities of general structure, is allied by its organisation to the Saurian or Lizard family, and, consequently, to the Ichthyosaurus.

The Plesiosaurus presents, in its organic structure, the most curious a.s.semblage we have met with among the organic vestiges of the ancient world. The Plesiosaurus was a marine, air-breathing, carnivorous reptile, combining the characters of the head of a Lizard, the teeth of a Crocodile, a neck of excessive length resembling that of a Swan, the ribs of a Chameleon, a body of moderate size, and a very short tail, and, finally, four paddles resembling those of a Whale. Let us bestow a glance upon the remains of this strange animal which the earth has revealed, and which science has restored to us.

The head of the Plesiosaurus presents a combination of the characters belonging to the Ichthyosaurus, the Crocodile, and the Lizard. Its enormously long neck comprises a greater number of vertebrae than the neck of either the Camel, the Giraffe, or even the Swan, which of all the feathered race has the longest neck in comparison to the rest of the body. And it is to be remarked, that, contrary to what obtains in the Mammals, where the vertebrae of the neck are always seven, the vertebrae in birds increase in number with the length of the neck.

[Ill.u.s.tration: Fig. 102.--Skeleton of Plesiosaurus dolichodeirus restored. (Conybeare princ.i.p.ally.)]