Page:Popular Science Monthly Volume 66.djvu/152

148 from sinking too deeply in the soft mud. The hand very rarely impresses, and but one instance is known of a dragging tail. What this uncouth brute looked like, one can not even imagine, for no skeletal remains are known which it in the least resembles.

One very numerous group of large bird-like tracks unaccompanied by hand or tail impressions seems from the blunted claws to have been those of plant feeders, but of this we can not be sure, for the condor of the Andes is also blunt clawed, and suggests the possibility that the makers of these tracks may also have been carrion feeding, which would place them among the carnivores. Certain it is that they were dinosaurs, and among the largest of the valley forms, though probably but half the bulk of their successors in the later rocks. One huge footprint from Northampton, Mass., measures twenty inches in length and holds four quarts of water.

There must have been quite a host of quadrupedal forms in the Triassic days, mainly of small size, but while they were probably of amphibian or reptilian origin nothing was really known of them until very recently. Professor Marsh found, some years ago, the remains of one animal, but unfortunately only the impression of the armor of the back remained, and, as the limbs were lacking, nothing could be learned of its probable footprints. A second specimen has just been brought to light, found in the village of Longmeadow, Mass., sufficient of which is preserved to show that the creature was long of limb and was probably a rapid runner. From its size and proportions, it corresponds very closely with one of the most numerous of the quadrupedal tracks. The Longmeadow specimen belongs to a group of primitive crocodile-like reptiles, to which Professor Huxley has given the name of Parasuchia. The footprints are small, but with a long interval between the successive tracks, with sharp claws, with four toes on the foot and five on the much smaller hand. Thus far only may we interpret the quadrupedal footprints with any assurance, for beyond this we are in the realm of almost pure conjecture, which in footprint interpretation has thus far nearly always proved wrong.

To summarize briefly, the footprint fauna contains amphibians, reptiles, and possibly birds; of the first we as yet know nothing, but we may be reasonably sure that they occurred; of the reptiles we have identified numerous dinosaurs, representatives of both great land-inhabiting orders, and we have also found indications of early crocodile-like forms. Other reptilian orders were doubtless present, but what they were we have as yet no means of knowing. Finally the only creatures which could have been birds could as readily have been dinosaurs and such in all probability they were.