ARE BIRDS DERIVED FROM DINOSAURS?

A 1879 Debate Between Prof. Benjamin F. Mudge and Dr. Samuel W. Williston

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Copyright © 2004-2009 by Mike Everhart

LEFT: Cast of the Berlin specimen of  Archaeopteryx in the Teylers Museum, Haarlem, Netherlands.

Mudge, B. F. 1879. Are birds derived from dinosaurs? Kansas City Review of Science and Industry 3:224-226.

ARE BIRDS DERIVED FROM DINOSAURS ?

     We hear, repeatedly, that the Dinosaurs are the ancestors of birds, or the stock from which the latter have been derived by evolution. A few points of resemblance, first noted many years ago, have been constantly repeated, without considering the numerous other points of dissimilarity which a more thorough knowledge of new genera and species has afforded. The fact that the bones of the hind feet of a few species closely resemble those of birds, and some of the bones were hollow, gave rise to the hasty conclusion that other resemblances would be found, and that the bird was the outgrowth of the reptile. While a few foreign species have three toes, like the bird, some of the European and nearly all of the American, have four and five toes, and the structure, and number of bones to the toe are closely reptilian. When there is a divergence from the reptilian type the feet approach the mammalian structure more than that of birds. This is seen in the numerous species and genera of the Sauropoda. In all cases, also, where there are but three toes, and those in structure are like the birds, the other bones of the foot and leg do not approach the type of the birds. When four toes are seen in the dinosaur, the fourth never turns backward like that of the bird. That most characteristic bone in the bird - the tarso-metatarsus - is, in the dinosaur, represented by the usual number characteristic of the reptiles, namely, five to eight, bones instead of one; and in no case is there a tendency to consolidate. The tibia and fibula of birds are consolidated, while in the dinosaurs these bones are always separate.

     It will be seen that if the legs of the dinosaur tended to a development

toward the bird structure, this development is not harmonious, as it should have been; but in the few cases where the toes are bird-like, the other bones of the foot and leg show no such tendency.

     Following the structure of the skeleton further, we find the pelvic bones of the bird always consolidated; those of the dinosaur never. Except in a few cases these bones are very different in shape. The termination of the caudal vertebra of the the dinosaur is always small and does not tend toward the plowshare structure of birds. 

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     A still more marked feature is the want of approximation of the dinosaur to the bird, in the sternum or breast-bone. This, in the bird, is the bone more than any other, which is mostly enlarged and singularly developed. Even in the ostrich and fossil Hesperornis, and other birds without wings, it is a large, massive bone. But in the thirty-five or more genera, embracing more than twice that number of species, of dinosaurs, only two have any trace of a sternum, even cartilaginous. In one European and one American species there is a small, slender, flat sternum, entirely unlike that seen in the bird, very reptilian in its structure. It has no shape that can be simulated to that of the bird. As a necessary result the clavicle (furculum), so marked in birds, is also wanting, though a rudimentary one is inferred in Apatosaurus.

     The differences between the wing bones and those of the front feet of the dinosaur are as marked as in any other portion of the skeleton. If the one had been the outgrowth of the other, then we should have seen an e___ and more rapid change in the fore foot of the reptile, than in the hind foot, inasmuch as the wing is far different in shape from the foot. But when the dinosaur has but three toes, like a bird, in the hind foot, (losing two from the typical reptile foot,) the fore foot has four toes. When the dinosaur has four toes in the hind foot, there are five in the front foot, all clinging to the reptilian type, and showing no divergence in the shape or structure toward the two closely united fingers of the wing. If the bird were a descendant, by evolution, from the dinosaur, the change of a foot to a wing should have begun early, and the development should have been more marked and rapid than that of the hind foot. But no indications of such change is seen, or the slightest tendency to form a wing, in all the fifty or sixty species of dinosaurs that have been described.

     The hollowness of the bones is less a marked feature of the dinosaurs than is usually supposed, and cannot be considered a marked characteristic; as more than half of the genera have no pneumatic cavities like birds, but bones of the solid or medullary structure of mammals. In Camarasaurus of Cope the hollow chambers assume a singular structure entirely unlike that of birds. The long bones are solid or medullary; but the vertebræ, which in birds are solid, have open re-entering cavities, which add lightness and strength, and may have been pneumatic. But the hollowness, such as it is, has no resemblance to that of the long bones of birds.

     The articulations of the vertebræ, when not retaining the reptilian traits, are more like mammals than birds. The bird articulation, so peculiar and so persistent, sometimes called " saddle-shaped," is not found in any dinosaur. But in the fossil Ichthyornis (first discovered by the writer in Kansas), a bird in this respect of low type, the vertebræ do not approach any form peculiar to the dinosaurs, but are fish-shaped, or bi-concave.

     It will thus be seen that, while in a few features there may be some resemblances between dinosaurs and birds, just as there are between the former and mammals, the details of the structure of the skeletons show, as a whole, very widely

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different elements. The dinosaurs vary so much from each other that it is difficult to give a single trait that runs through the whole. But no single genus, or set of genera, have many features in common with the birds, or a single persistent, typical element of structure which is found in both.

     The geological position of the dinosaurs, too, precludes the idea that they are the ancestors of the birds. They appear at the same time (in the Triassic) as the birds, instead of preceding them, and they continue to the Eocene; and the later specimens do not approximate any nearer to bird forms than the first.

     If the birds were derived, by process of evolution, from the dinosaurs, then the latter should have appeared first, and, as geological time progressed, should, harmoniously, in every organ, assume a nearer and nearer approach to the bird type, and finally disappear in the flying biped. When it became a bird, it should have ceased to be a Dinosaur, just as a child disappears in the man. The last one at the close of the Cretaceous, when the type became extinct, had no nearer an approach to the bird than the earliest in the Triassic. Laosaurus, which, of all the twenty-seven American genera, approaches in the toes and pelvis nearest to birds, is found in the Wealden ; and, in legs, fore feet, and absent sternum, has no approximation to a bird.

     No dinosaur has ever shown a fore foot approximating in the slightest degree to a wing. The first bird was as distinctly a bird, with feathers and wings, as any now living. True, Archæopteryx had a tail of twenty vertebræ, but that is an appendage in common with the lowest reptile and the monkey, and does not ally it to the dinosaurs any more than to those animals. The fossil birds differed as strongly from each other as those now living. The Hesperornis and Ichthyornis lived and ran out together, the one without wings and with a common bird vertebræ; the other with strong wings and a fish-like vertebra. Others lived with them closely allied to living species.

     With so little to sustain the evolution of the bird from the dinosaur, can it be accepted as a geological fact ?

Williston, S. W. 1879. Are birds derived from dinosaurs? Kansas City Review Science and Industry 3:457-460.

"ARE BIRDS DERIVED FROM DINOSAURS ?"

BY DR. S. W. WILLISTON, NEW HAVEN, CONN .

     I have read with interest an article in the August number of this magazine upon the above subject, by my friend Prof. B. F. Mudge. Unlike most writers opposed to the doctrine of evolution, Prof. Mudge's views are conscientiously drawn from purely scientific grounds, as a long and pleasant acquaintance with him fully assures me, and as such are worthy of careful consideration.

     The confused state of general literature upon the palæontology of vertebrates, a science yet in its infancy, has led the Professor in to a few misapprehensions, and I will here endeavor to give the views now held to sustain the Dinosaurian genesis of birds.

     The relationship of dinosaurs and birds was pointed out and ably discussed by Prof. Huxley in 1861, and the replies of Prof. Owen are well known. The

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additions to our knowledge of these extinct forms since then, though they may modify his reasons somewhat, have not destroyed their cogency. Anatomists, however, are not prepared to state the evolution of birds from dinosaurs as a geological fact, but its soundness as a theory, it seems to me, cannot be readily questioned.

     The persistence of certain geological types is constantly adduced by its opponents as contrary to the belief in Derivation. That many genera, possibly species, of low forms have persisted, even from Palæozoic times to the present, proves not that they were immutable, but that their surrounding circumstances remained the same - that they filled places in nature that no other types could replace. The true dinosaurs came into existence in the Triassic, and continued as a type to the very close of the Cretaceous, simply because in the struggle for life their place was not invaded; but, on the other hand, at any time during that period they may have given off branches that developed upward into birds, or, possibly, downward into the less specialized sauropoda. While some became birds, there, was still a place for others as dinosaurs, and, as such, others filled it. That the type of dinosaurs should have progressed harmoniously into birds, as the child disappears in the man, at first sight may seem reasonable enough, but if we follow such views to their logical conclusions, the absurdity is apparent. If there had been no splitting, or divergence of types, man to-day would be the only form of life upon the globe - the result of harmonious progression from the lowest to the highest. Hence it will be readily enough seen that for dinosaurs to become extinct upon the appearance of birds, is precisely contrary to what we should expect.

     But few now believe in the avian origin of the Connecticut valley Triassic footprints. They were undoubtedly made by dinosaurs and of highly developed forms, as their osseous remains show (Megadactylus). The earliest known birds are the species of Archæopteryx, from the Jurassic of Solenhofen. Hence, with our present knowledge, there was an abundance of time for a development to have occurred. These earliest birds, of which but very few species have been discovered, are of a far lower or more reptilian type than any now living, and have been properly placed in a distinct sub-class. The Archæopteryx was a bird covered with scale-like feathers, and possessed of reptilian-like teeth set in sockets, wings with four functional fingers, and a long slender vertebrated tail. The next forms of birds now known are from the Cretaceous, of which, probably, none can be classed among the modern forms. In the Hesperornis, from Kansas, we have birds with teeth and very rudimentary wings. Their bones were also solid, a peculiarity yet found in the penguin and allied forms. In the Ichthyornis, from the same locality and horizon, in addition to teeth, we find the neck vertebræ biconcave, a peculiarity reptilian as well as ichthyic.

     The Professor errs in drawing any comparisons from the sauropoda. They are not true dinosaurs, and may eventually be entirely separated from the order. It is very true that scarcely a single trait of structure runs through the whole

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of Dinosauria; but that fact does not affect the relation existing between the most avian dinosaurs and the most reptilian birds. One would not compare a turtle with an eel to show the resemblance between reptiles and fishes.

     About ten thousand species of living birds are known; but from the earlier geological ages we are acquainted with scarcely a dozen in any degree of completeness. As I have stated, these few forms are the most reptilian, and they certainly give us no reasonable grounds for supposing that other, and numerous, undiscovered contemporaneous forms were of the modern specialized types. While it may be said that there is not a single persistent typical element of structure common to both classes, it may also be said that there is scarcely a single persistent element of structure now known to separate them. As reptilian characters among birds, we have: long bones solid; wingless, or wings with four functional fingers; long, slender, vertebrated tail; slender, recurved teeth, set in sockets; vertebrae bi-concave; ischial and pubic bones with free extremities; fibulæ free from tibiæ and descending well toward the tarsus; three toes, all directed forward, etc. As avian characters among the highest forms of dinosaurs: long, slender, very hollow bones; fore legs very short, feeble, and not used in locomotion; sacrum of numerous consolidated vertebræ; ischiæ and pubes directed backward and parallel; femora shorter than tibiæ and with fibular ridges at lower extremities; fibulæ slender and partially united to tibiæ (Marsh) ; astragali united to tibiæ (Ornitho-tarsus); three toes only. Many of these resemblances are important and can scarcely be called accidental. About the only persistent characters of any degree of importance among birds are the early ossifications of the pelvic and metatarsal bones.

     Of the nature of the sternum among dinosaurs we have little definite knowledge. It, as well as the skull, is known in a very few species. That it may be birdlike in the true dinosaurs, is evident from the Sauropodous Ceteosaurus, where it is broader than long. Indeed, in Palæontology, we can predicate but little from the absence of any anatomical feature, as the clavicle among dinosaurs. Future discoveries may very materially change our pre-conceptions based upon negative evidence.

     It is not difficult to understand how the fore legs of a dinosaur might have been changed to wings. During the great extent of time in the Triassic, in which we have scanty records, there may have been a gradual lengthening of the outer fingers and greater development of the scales, thus aiding the animal in running. The further change to feathers would have been easy. The wings must first have been used in running, next in leaping and descending from heights, and, finally, in soaring.

     It is not necessary to suppose that birds came into existence before mammals, or even that the latter were derived from true reptiles. There is certainly no reason why lower types may not have succeeded higher ones. The theory of Derivation does not necessarily mean unbroken progression, but rather adaptation to circumstances. The absence of teeth among mammals may indicate degradation,

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for their presence and use usually require greater mental and muscular activity. The absence of teeth among birds is a specialization brought about by changed habits of life, and does not mean degradation. The rank of any species cannot be based upon any single detail of its anatomy, but only upon its assemblage and complexity of characters.