The New International Encyclopædia/Bird, Fossil
BIRD, Fossil. Fossil remains that could be referred to birds were among the later acquisitions of paleontologists. The first were mistakenly so considered, and consisted of the famous ‘bird-tracks’ discovered in the ‘brownstone’ rocks of the Connecticut River by Hitchcock, about 1835, and extensively studied by him. These footprints may possibly, in a few instances, be traces of primitive animals properly called birds, but so far as known all are impressions made upon mud by dinosaurs and similar amphibians or reptiles of the Triassic Age. (See Dinosauria; Stegocephalia, etc.) More recently true birds have been found fossil from the Jurassic Age onward, but their remains are everywhere comparatively scarce, due mainly to the easy destructibility of their bodies. The earliest to be identified proved to be also the earliest in time, and consisted of the remains in the Jurassic slates of Bavaria of Archæopteryx, whose characteristics are fully described under Archæopteryx. This seems to have been a true feather-clothed bird, with well-formed wings, but a long lizard-like tail, beset on each side with a row of horizontal quill-feathers, and a heron-like beak studded with teeth. These characteristics are so radically different from those of all other birds that the archæopteryx is classified in a subclass of itself termed Archæornithes; all other birds, fossil and recent, forming another subclass, Neornithes or Euornithes. A long gap in geological time separates the period of the archæopteryx from the next earliest fossil birds known, which belong to the upper, or more recent, part of the Cretaceous Age. These formations in Europe and India, but especially in the western United States, have yielded varied remains of large birds, which, because all have teeth in the beak, have been called Odontornithes or Odontoleæ. All are still of a low type of organization, showing many points of genetic affinity with reptiles, but far advanced beyond Archæopteryx; and all were aquatic and fish-eating. They approximate, indeed, so closely to the ordinary carinate birds of the present time that they are included with them in a single subclass, as above noted, of which, say Parker and Haswell, “they will constitute a separate series characterized by the possession of teeth and . . . that the two halves of the lower jaw remain completely separate in front, instead of having a solid bony union. Of these toothed birds the one type is known as Ichthyornis, and comprises somewhat gull-like birds characterized by having a numerous series of teeth implanted in distinct sockets, and also by the vertebræ or joints of the back articulating with one another by means of cup-like surfaces (instead of saddle-shaped). . . . It is quite within the bounds of possibility that these birds may be ancestral types of the modern gulls. With Hesperornis (q.v.) we are confronted with a totally different type, in which the teeth were implanted in an open groove, while the wings were rudimentary and the keel of the breast-bone was wanting, although the vertebræ resembled those of existing birds. In general organization, Hesperornis, indeed, approximated very closely to the modern divers. . . . That it was thoroughly aquatic in its habits is self-evident; while it may . . . be regarded as a specialized and flightless offshoot from the ancestral stock of the modern divers.” The discovery and elucidation of these Cretaceous toothed birds was made chiefly by Prof. O. C. Marsh, of Yale L'niversity, between 1870 and 1880, and his novelties included a large number of skeletons or fragments which have been referred to various genera and are preserved in the Yale Museum at New Haven. “They afford a most valuable contribution in favor of the doctrine of evolution, approximating more and more, as we descend in the geological scale, to reptiles, from which it may be confidently stated the avian class has originated.”
With the closing of the Cretaceous Period, toothed birds seem to have disappeared, for bird-fossils from the early formation of Tertiary age lack them, and in general approach closely to modern types. Few of these fossils have been found in North America, but Europe and South America have supplied many genera and species of various groups, increasing in numbers as we rise in the geologic scale. Among the oldest (Eocene) were certain gigantic forms, characterized by long, powerful legs and small and apparently useless wings, but especially by “the enormous and ponderous structure of the skull, which is quite unlike that of any recent bird, and seems out of all proportion to the limbs, gigantic as are some of the leg-bones.” These have been combined into a group (Stereornithes) including many species, chiefly of the genera Brontornis and Phororhacos, from the Miocene of Patagonia. “Brontornis, for example,” according to Lucas, “had leg-bones larger than those of an ox; . . . while the great Phororhacos, one of his contemporaries, was not only nearly as large, but quite unique in build. Imagine a bird seven or eight feet in height, from the sole of his big, sharp-clawed feet to the top of his huge head, poise this head on a neck as thick as that of a horse, arm it with a beak as sharp as an ice-pick and almost as formidable, and you have a fair idea of this feathered giant of the ancient pampas.” The skull equaled in size that of a large horse, but whether this great equipment was used for carnivorous purposes can only be conjectured. The general affinity of these huge birds seems to be with the herons; and with them have been classed Gastornis and certain other large forms of contemporary time in Europe and North America, whose habits are supposed to be those of cursorial birds of prey. Other birds of the early Tertiary Age represented the Steganopodes (q.v.), or were similar to gulls, penguins, cranes, kingfishers, game-birds, and many other modern types. The rocks and caves of the Paris Basin, and of central France, and the Eocene beds of Wyoming, have been particularly fruitful in ornitholites. The Miocene and Pliocene eras furnish still more fossil forms, among which a large number of genera still exist, showing how early birds arrived at the perfection of their form and adaptation. Lydekker tells us that by far the greater portion of the remains of birds from the still higher Pleistocene rocks seem to be generioally if not specifically identical with those now inhabiting the district in which they occur, though their range at that time may have been different from its present extent. To this period, immediately precedent to that in which we live, belong such recently existing races as the moa, epiornis, dinornis, etc., but they are treated elsewhere.
Consult: Newton, Dictionary of Birds (London, 1893-96); Oiseaux fossiles de la France (Paris, 1867-71); Marsh, Odontornithes, a Monograph of the Extinct Toothed Birds of North America (Washington, 1880); Lucas, Animals of the Past (New York, 1901) ; Case, “The Development and Zoölogical Relations of the Vertebrates Aves-Mammalia,” in The Journal of Geology (Chicago, 1898). See also, for further references and particulars, Birds; Extinct Animals; Archæopteryx; Hesperornis; Moa, etc.