BIRDS, Fossil.. While the animal and vegetable kingdoms of thepaleontologist extend to as wide, or rather a wider, range than those of the historian of modern life, yet several divisions are scantily represented in the petrified remains preserved in the stony records of the earth's crust. This was to be expected from the conditions under which these fossiliferous strata were deposited. As these rocks are aqueous, chiefly marine, the relies of plants and animals whose natural habitats were in or near the water, must be common in a fossil state, whilst the remains of others with different habits will be comparatively rare, if present at all. Birds belong to this latter class. Their power of flight would save them from numerous casualties which would prove fatal to quadrupeds; and even if they did perish in water, the lightness of their bodies, produced by their internal cavities and the quantity of their feathers, would keep them floating until they decomposed, or became the food of predaceous animals.
The earliest traces of birds consist of footprints on red argillaceous sandstones in the valley of Connecticut river, North America. These sanastones, though long consid ered of n much older date, have been, on the best evidence, referred by the brothers Rogers to the oolitic period. The beds had formed an ancient sea-beach, and over it, dur ing tha recession of the tide, had marched the animals, which have left on them their foot steps. Before the return of the title, the inequalities had been filled up with dry air drifted sand and mud, and on this was deposited a new layer of silt. The beds often exhibit ripple-marks, and occasionally small circular depressions, which have been formed by drops of rain. The traces of thirty-three species of B. have been distinguished; with them are associated the impressions of various lizards, chelonians, and batrachians, The size of the ornithielinites (Gr. a bird, and fano?" a trace or footprint), as the bird-tracks are called, so far exceed those that would be made by the largest living birds, that it was doubted whether their origin had been satisfactorily explained, until the discovery, in New Zealand, of the remains of the dinOlitiS. In one species the imprint of
the foot measures 15 in. in length, and 10 in. In breadth, excluding the hind claw, which is 2 in. long. The distance of the impressions from each other varies from 4 to 6 feet. These measurements indicate a bird about four times the size of an ostrich, but probably not much larger than some species of The footprints are for the most part trifid, and show the same number of joints as exist in the living tridactylous birds.
No indications of the existence of birds have been discovered in the rocks of the •creta ceous period. It does not follow, however, that the class arcs had no representatives dur ing the ages when the chalk was being deposited. This is a deep-sea formation, and for the reasons already stated, it is not to be expected that the remains of this class should be found iu these measures. And so also it would be rash to conclude that the oolitic foot prints give the date of the first appearance of B. on the globe. The bone of cilniliornis diomedevs, found in the chalk, which was described by prof. Owen as part of the humerus of a bird, is now believed to belong to a pterodactyle.
No true fossil remains of B. have been discovered in rocks older than the eocenc gypseous deposits of Montmartre, where ten species have been found. Seven species have been described from strata of the miocene period, the most important of which have been found in the Sewalik beds, associated with the remains of huge proboscides. But the pleistocene deposits have supplied more than half of the known fossil birds. The most remarkable of these are the bones of huge struthious B. of the genera dinornis (q.v.), palapteryx (q.v.), and aptornis. Dr. Mantell mentions the fossil eggs and bones of a bird still larger, called the tepyornis, from Madagascar.