The oldest bird of which we have any knowledge, called the Archaeopteryx, or Lizard-tailed bird, the latter name from its slender lizard-like but curiously feathered tail, is found fossil in the lithographic slates of Solenhofen, Bavaria, where its presence was first made known by the discovery in 1861 of the impression of a single feather. The existence of a bird in a geological horizon of such relatively great antiquity as this Upper Jurassic was at first somewhat doubted, but a year or two after the first discovery a second specimen, showing much of the skeleton, was obtained, and in 1877 another, these being all thus far secured. The example found in 1863 is now preserved in the British Museum, London, while the last, and as it proves, best example, is in the Berlin Museum. These two specimens, which are sometimes regarded as representing two distinct species (Archaeopteryx lithographica and A. siemensi), supplement each other, and from them a fairly complete account may be gleaned of this remarkable bird. They have been very minutely studied by many eminent anatomists, as becomes their importance in affording almost our only actual knowledge of the transition between reptiles and birds.
Anatomy, Size, etc. ; The Lizard-tailed bird was apparently about the size of our common Crow, being nearly eighteen inches in length. It had apparently a long, narrow body, while the head was small, pyramidal, nearly flat on top, and provided with large openings for the eyes. The upper jaw, and probably the lower as well, was provided with numerous teeth, which appear to have been set in a groove. There was no beak, for the teeth extended to the very tip of the jaw. The backbone consisted of some fifty biconcave vertebrae, of which number ten or eleven are regarded as belonging to the neck, a less number than is known in any modern bird, the lowest number being thirteen.
In place of the short, usually solid bones of the tail found in present birds, Archaeopteryx had a long, slender tail of about twenty free bones exactly as in many reptiles. Certain of these bones, perhaps each of them, supported a pair of long tail feathers. These feathers at present lie at an angle of about thirty degrees to the bones of the tail, and as they are pretty closely matted together, it is difficult to determine the exact number, some students placing them at twenty pairs, and others, as Gadow, as low as twelve pairs; the truth perhaps lies somewhere between these extremes. Present knowledge does not permit a positive assertion that the tail could be raised or depressed at will, or the pairs of feathers spread or closed, though both conditions might readily have been possible, for a very small tendon would have been ample provision for the manipulation of these parts without any trace of its presence appearing on the bones.
Archaeopteryx had four toes, and the whole leg and foot appeared very much like those of an ordinary perching bird, except that the tibia and fibula were distinct, as in most reptiles. The anterior limbs, however, are very curiously modified. The wings were rather short and rounded very much as in the common fowl, but unlike all known birds there were three long, slender fingers on each wing, each of which was armed with a hooked, sharp-edged claw. There were also relatively large flight feathers, the apparent number being seventeen in each wing, six or seven of which were primaries and the rest secondaries, and, it may be added, no other bird has so few primaries. In addition to the quills there was at least one row of wing-coverts.
The sternum, or breast-bone, is obscurely preserved and is more or less in doubt, some observers claiming that it is not only present but possesses a well-defined keel, while others declare that, although much has been written about it, nothing is absolutely known. A definite knowledge of this bone would be of great assistance in interpreting the probable habits of its owner. The three bones of the pelvis, as in most reptiles, are perfectly distinct from one another, and a further decidedly reptilian character is found in the absence of the hook-like processes of the ribs.
The covering of the body, aside from the wing and tail feathers, has been the subject of much speculation. From the fact that the feathers of tail and wings are preserved with such remarkable fidelity, it is argued that, had there been a general feather covering, some definite trace of it would remain. As it is, the only positive contour feathering seems to be confined to the leg, producing apparently a “booted” condition similar to that observed in the Falcons. There is also some slight evidence of the presence of a “ruff” about the base of the neck, as in the Condor, while the remainder of the body was apparently naked, or possibly covered with down or small feathers which disappeared during the decay which preceded the entombment. The contention advanced by certain writers that the body, aside from the feathering mentioned above, was covered with scales is not only absolutely unsupported by fact, but is in the highest degree improbable. The length of time that must have intervened in evolving the very perfect wing and tail feathers of Archaeopteryx from reptilian scales, if that is whence they came, would undoubtedly have been ample for the production of some sort of a feather covering for the remainder of the body.
Probable Habits. With the above facts before us we are perhaps in position to indulge in some fairly reasonable speculation as to the habits of this ancient bird. From the presence of a distinctly perching foot it may be inferred that a considerable portion of its life was spent in trees, which are known to have been abundantly present at that time, and further, that the curious hooked fingers were of assistance in climbing about among the branches, as are those of a young Hoactzin of today. On account of the relative slenderness of both legs and feet, and to their position far back on the body, Mr. Beddard, a distinguished English anatomist, doubts if the Archaeopteryx could have stood erect. On the ground he thinks it must have assumed a quadrupedal position. In support of the opposite view it may be stated that the tips of the wing-quills are not worn or injured, as they almost certainly would have been had they habitually come in contact with the ground. But this is a point that obviously cannot be definitely settled.
The fact that no openings have been observed for the admission of air into the bones has been taken by several writers to militate against flight. This is certainly a very unsafe generalization, for, as already pointed out, certain birds, as for example the Swallows, that are past masters in the art of flying, have practically non-pneumatic bones, while others, as the Ostriches, have the bones highly pneumatic, yet cannot fly at all. Although the wings were rather short and rounded, the well-developed wing feathers, which appear adequate for the support of a bird of this size, seem to indicate beyond reasonable doubt that Archaeopteryx could fly, though perhaps it was incapable of long-sustained flight. The Tinamous furnish an example in point. They have short, rounded wings and can fly well for short distances, but soon become exhausted. If we possessed a more satisfactory knowledge of the breast-bone, we should be the better able to decide regarding the probable power of flight, for if this was actually absent or very much reduced in size, it would appear to militate against the enjoyment of any great power of aerial locomotion. It may be added, as was pointed’ out by Professor Lydekker, that the slight development of the deltopectoral crest of the humerus apparently indicates at least weak power of flight.
As to the food of the Archaeopteryx we of course know nothing, but from the presence of the numerous distinct and rather sharp teeth it may be inferred that these were still of assistance in procuring food, which likely consisted of animals of some kind. But this is largely speculation.
All things considered, Archaeopteryx was a most remarkable animal. While it possessed numerous points of structure unmistakably similar to those of reptiles, it was, on the whole, much nearer to the birds than to the reptiles. It is clearly a connecting link between the two classes, and yet we are undoubtedly still very far from the original point where the branch was made from the reptilian stem. Indeed, the reptiles as we know them may be very unlike what they were when the division occurred which ended in Archaeopteryx on the one hand and modern reptiles on the other. In any event it must have taken a very long period of time for the development of such distinctly bird-like feet and feathers. Archaeopteryx is well entitled to be placed in a Subclass, opposed to all other known birds.
In 1881 Professor O. C. Marsh described, under the name of Laopteryx priscus, a crushed and broken skull and a single detached tooth that may or may not have belonged to it, from the Jurassic beds of Wyoming. This has been supposed to be the skull of a bird, and, for no other reason than that it is found in beds of similar geological age, has sometimes been placed in the Subclass with Archceopteryx. It now seems more than likely that it will be proved to belong to the reptiles, and in any case too little is known of its structure to definitely associate it with Archaeopteryx.