Animals of the Past

by Frederic A. Lucas

Fig. 14.—Nature's Four Methods of Making a Wing. Bat, Pterodactyl, Archæopteryx, and Modern Bird.

We get some side lights on the structure of primitive birds by studying the young and the earlier stages of living species, for in a very general way it may be said that the development of the individual is a sort of rough sketch or hasty outline of the development of the class of which it is a member; thus the transitory stages through which the chick passes before hatching give us some idea of the structure of the adult birds or bird-like creatures of long ago. Now, in embryonic birds the wing ends in a sort of paw and the fingers are separate, quite different from what they become a little later on, and not unlike their condition in Archæopteryx, and even more like what is found in the wing of an ostrich.

Then, too, there are a few birds still left, such as the ostrich, that have not kept pace with the others, and are a trifle more like reptiles than the vast majority of their relatives, and these help a little in explaining the structure of early birds. Among these is a queer bird with a queer name, Hoactzin, found in South America, which when young uses its little wings much like legs, just as we may suppose was done by birds of old, to climb about the branches. Mr. Quelch, who has studied these curious birds in their native wilds of British Guiana, tells us that soon after hatching, the nestlings begin to crawl about by means of their legs and wings, the well-developed claws on the thumb and finger being constantly in use for hooking to surrounding objects. If they are drawn from the nest by means of their legs, they hold on firmly to the twigs, both with their bill and wings; and if the nest be upset they hold on to all objects with which they come in contact by bill, feet, and wings, making considerable use of the bill, with the help of the clawed wings, to raise themselves to a higher level.

Fig. 15.—Young Hoactzins.

Thus, by putting these various facts together we obtain some pretty good ideas regarding the appearance and habits of the first birds. The immediate ancestors of birds, their exact point of departure from other vertebrates, is yet to be discovered; at one time it was considered that they were the direct descendants of Dinosaurs, or that at least both were derived from the same parent forms, and while that view was almost abandoned, it is again being brought forward with much to support it. It has also been thought that birds and those flying reptiles, the pterodactyls, have had a common ancestry, and the possibility of this is still entertained. Be that as it may, it is safe to consider that back in the past, earlier than the Jurassic, were creatures neither bird nor reptile, but possessing rudimentary feathers and having the promise of a wing in the structure of their fore legs, and some time one of these animals may come to light; until then Archæopteryx remains the earliest known bird.

In the Jurassic, then, when the Dinosaurs were the lords of the earth and small mammals just beginning to appear, we come upon traces of full-fledged birds. The first intimation of their presence was the imprint of a single feather found in that ancient treasure-house, the Solenhofen quarries; but as Hercules was revealed by his foot, so the bird was made evident by the feather whose discovery was announced August 15, 1861. And a little later, in September of the same year, the bird itself turned up, and in 1877 a second specimen was found, the two representing two species, if not two distinct genera. These were very different from any birds now living—so different, indeed, and bearing such evident traces of their reptilian ancestry, that it is necessary to place them apart from other animals in a separate division of the class birds.

Archæopteryx was considerably smaller than a crow, with a stout little head armed with sharp teeth (as scarce as hens' teeth was no joke in that distant period), while as he fluttered through the air he trailed after him a tail longer than his body, beset with feathers on either side. Everyone knows that nowadays the feathers of a bird's tail are arranged like the sticks of a fan, and that the tail opens and shuts like a fan. But in Archæopteryx the feathers were arranged in pairs, a feather on each side of every joint of the tail, so that on a small scale the tail was something like that of a kite; and because of this long, lizard-like tail this bird and his immediate kith and kin are placed in a group dubbed Saururæ, or lizard tailed.

Because impressions of feathers are not found all around these specimens some have thought that they were confined to certain portions of the body—the wings, tail, and thighs—the other parts being naked. There seems, however, no good reason to suppose that such was the case, for it is extremely improbable that such perfect and important feathers as those of the wings and tail should alone have been developed, while there are many reasons why the feathers of the body might have been lost before the bird was covered by mud, or why their impressions do not show.

It was a considerable time after the finding of the first specimen that the presence of teeth in the jaws was discovered, partly because the British Museum specimen was imperfect,[6] and partly because no one suspected that birds had ever possessed teeth, and so no one ever looked for them. When, in 1877, a more complete example was found, the existence of teeth was unmistakably shown; but in the meantime, in February, 1873, Professor Marsh had announced the presence of teeth in Hesperornis, and so to him belongs the credit of being the discoverer of birds with teeth.