GROUP OF SMALL FLYING DRAGONS, OR PTERODACTYLS.
Rhamphorhynchus phyllurus.
Pterodactylus crassirostris. Dimorphodon macronyx.
Pterodactylus spectabilis.
Whether Pterodactyls were cold-blooded or warm-blooded is a question on which the authorities are not agreed. Professor Owen argued from the absence of feathers that they could not have been warm-blooded. But, in spite of this great authority, who has defended his opinion somewhat strongly, there are others who argue that the amount of work involved in sustaining a Pterodactyl in the air make it highly probable that it was warm-blooded. The absence of feathers to retain the heat of the body need not be regarded as conclusive, for bats are warm-blooded animals, and in their case the heat of the body is retained by a slight downy covering to the skin. Such a covering may have protected the bodies of Pterodactyls, and we could not expect to see any trace of it in the Bavarian specimen of Rhamphorhynchus referred to above. An important fact bearing on this question is the discovery of perforations in the bones of these animals very similar to those seen in birds. Now, birds have a wonderful system of respiration, or breathing. The air they breathe passes, not into their lungs only, but penetrates to the remotest parts of their system, filling their very bones with life, and endowing them with activity and animation adapted to their active aërial existence. It may, therefore, be argued that Pterodactyls breathed much in the same way; that their bones, too, were supplied with air by an elaborate system of air-sacs, and that they had lungs like those of birds. We cannot, however, stop there, but are led on by physiological reasoning to conclude that the circulation of the blood must have been rapid, and that the heart was like that of birds and mammals, four-celled. It would therefore follow—since birds and mammals are warm-blooded—that Pterodactyls were also. Such, at least, is the view of Professor H. G. Seeley, who says of the Cambridge specimens, "That they lived exclusively upon land and in air is improbable, considering the circumstances under which their remains are found. It is likely that they haunted the sea-shores, and, while sometimes rowing themselves over the water with their powerful wings, used the wing-membranes, as the bat does, to enclose their prey, and bring it to the mouth.
“The large Cambridge Pterodactyls probably pursued a more substantial prey than dragon-flies. Their teeth are well suited for fish, but probably fowl and small mammals, and even fruits, made a variety in their food. As lord of the cliff, it may be presumed to have taken toll of all animals that could be conquered with tooth and nail. From its brain it might be regarded as an intelligent animal. The jaws present indications of having been sheathed with a horny covering.”
Probably the large Pterodactyls of the Cretaceous period, soaring like albatrosses and giant petrels over the surface of the ocean, co-operated with the marine reptiles, such as Ichthyosaurs, Plesiosaurs, crocodiles, and others, as those sea-birds now do with the whales, porpoises, and dolphins, in reducing the excessive numbers of the teeming tribes of fishes, and in maintaining the balance of oceanic life.
With regard to the place of Pterodactyls in the animal kingdom, Professor Seeley places them as a distinct sub-class, side by side with birds, and between mammals and reptiles, thus—
| Mammalia. | ||
| O r n i t h o s a u r i a | A v e s | |
| Reptilia. |
The name Ornithosauria (bird-lizards) is frequently used instead of the other name, because it expresses the idea of their being partly saurian, and partly bird-like.