Birds – American Tooth Birds – Hesperornis

The first of these orders to be considered is typified by what has been named the Hesperornis, signifying literally “western bird,” since at the time of its discovery the locality where it was found was beyond the western limits of extensive settlement. Hesperornis was a flightless, swimming and diving bird of great size, its length being nearly four feet. The skull was relatively small, while the bill or jaw was very long and slender, with its rami or branches united in front by a ligament only, and the component bones free from one another, as in reptiles. The teeth, which were replaced by a new one growing inside of and ultimately absorbing and pushing off the old one, are set in a continuous groove, and fill the lower mandible quite to the tip, while in the upper mandible they are confined to the basal portion or maxilla. The long and slender neck is made up of some seventeen saddle-shaped vertebrae, and was doubtless capable of rapid flexure and was thus of assistance in securing its prey. The wing was very much reduced, being represented by the humerus only, and was probably concealed beneath the skin or in any event among the feathers. Without going into a complete description of the shoulder girdle it may be said that its elements, as interpreted in the light of recent material, make it very similar to the arrangement found in recent birds and not nearly so similar to the reptiles as was formerly supposed, and further, the struthious characters are also decidedly less apparent than was believed. The body or pelvis was greatly compressed, while the legs and feet present some anomalous features. The femur was short and stout, the tibia very long and slender although somewhat pneumatic, the fibula slender, about three fourths the length of the tibia, and united to it by a cartilage only, while the metatarsus was relatively short and stout. The feet were four-toed, the outer toe being much the largest, and nearly twice the length of the third toe. Mr. F. A. Lucas was the first to call attention to the fact that the legs of Hesperornis were directed out-ward almost at right angles to the body, instead of downwards as in other birds, and that apparently they were naturally moved together like a pair of oars. There is also evidence to show that the toes were webbed as in the Grebes. This . peculiar arrangement of the legs, combined with the almost total absence of wings, must have made this bird practically helpless on land, to which it doubt-less resorted as rarely as possible, and then only for nesting purposes.

Some years ago Professor Williston discovered a fragmentary specimen which he thinks represents the plumage of Hesperornis, and if this is correct, it was covered with long, fluffy, hair-like feathers, which has been taken as another indication of its relationship with the Ostrich-like birds. This sort of plumage is seemingly but a poor adaptation for aquatic life, yet it is not wholly without parallel among recent birds, such for example as the Snake-birds (Anhinga), which are covered with a very loose and easily water-soaked feathering.

The life habits as interpreted by the structure, indicate that Hesperornis was carnivorous, feeding doubtless upon the fishes and other aquatic life that by permission of the publishers, McClure, Phillips & Co.)is known to have been abundantly present in the Cretaceous seas. Its narrow body and powerful legs and webbed toes point to its having been an expert swimmer and diver, enabling it to overtake its finny prey, in which it was assisted also by its long flexuous neck and numerous sharp, backward-pointing teeth.

As might be supposed the relationship of this remarkable bird has been the subject of much discussion and not a little difference of opinion, and so long as certain important parts of the skeleton remain unknown, its exact position must remain open to more or less question. It was at first regarded as a carnivorous, swimming Ostrich, but as already suggested, the structure does not at all bear out the claim of its struthious affinity, and moreover, as there is no authentic trace of the presence of the Ostrich in North America, this may be dismissed at once (cf. p. 63). By many it is regarded as being closely allied to, if not indeed the direct ancestor of, the Loons and Grebes, but as Mr. Lucas has very clearly shown, those portions of the skeleton which are thought to indicate kinship with the Loons and Grebes are only similarities of structure which have resulted from similarity of habits. And, as he has further pointed out, the anomalous condition would be presented of placing the strong-flying Loons and Grebes in the direct line of descent from a flightless bird, which would be “quite out of the question.” All things considered it would appear that Hesperornis was in many respects a very highly specialized type which has been blotted out without leaving any close relatives among living birds.

Other Forms. — In the same beds with Hesperornis regalis, the form above mentioned, two additional species of Hesperornis were described, one of which has recently been removed as the type of a new genus (Hargeria), and another wholly different flightless swimming bird known as Baptornis, or the “plunging bird,” in allusion to its probable diving habits. These are all imperfectly known, and a full desoription may be omitted.