BIRD, . 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 ; , 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 . 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
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.”