A Review of Some Recent Criticisms...

...of the Restorations of Sauropod Dinosaurs Existing in the Museums of the United States, with Special Reference to that of Diplodocus carnegiei in the Carnegie Museum

Continued from Part Three

The theory, which has been proposed by Dr. Hay, that it was impossible for these huge sauropods to rear upward, seems to me to be one that any one who has carefully studied the movements of animals, and especially of reptiles (turtles excepted), must repudiate. We know that certain of the smaller lacertilia to-day, when in rapid motion, assume a bipedal pose. Professor Osborn in one of his papers has given us a reproduction of the figure of Chlamydosaurus.

Fig. 18. Chlamydosaurus running. After Saville-Kent. Copied from Osborn.

Even more striking than the posture shown in this picture is the position constantly assumed by a well-known lizard of our southwestern and western country, Crotaphytus collaris Say. I regret that although I have had a number of these animals in captivity at our museum I never took the pains to have photographic snap-shots made of them when rapidly running across the floor. They assume when so doing a position in which the body is far more perpendicular than is the case in the picture before you, and they carry the tail even higher. Ordinarily these lacertilians crawl, trailing the tail behind them, but when alarmed they rise upon their hind feet and throw the tail upward, moving along with great speed. I do not advocate such a position for the tail of Diplodocus, but, simply because it is long, to declare therefore that it must have necessarily trailed with its whole length upon the ground, does not appear to me to be reasonable. Animals with tails relatively quite as long, and even longer, are known to-day to hold them elevated, and there was proportionately as much muscular power, as shown by the muscular attachments, in the tail of Diplodocus, as there is in the tail of a Crotaphytus or a Chlamydosaurus. To declare as Mr. Hay does, that these animals must have moved as crocodiles and could not by any possibility have raised themselves from the ground, does not appear to me to be logical. In fact, those of us who have hunted alligators know that in life even alligators raise themselves high upon their legs when running, and get away like a dog at a sort of a trot.

Tornier indulges in a lengthy criticism of the pose given to the feet in recent reproductions of the Diplodocus and demands that they shall be placed in a plantigrade position. He thus takes issue with Mr. Hatcher and with others who have carefully examined the subject. Professor Abel, of Vienna, in criticizing Dr. Hay's article, has very aptly pointed out that the manner in which the metacarpals articulate in the pes and manus indicates a more or less digitigrade position. Those of us who are familiar with the feet of the sauropod dinosaurs know very well that in their structure, as indicated by the facets of both the proximal and distal end, there is strong evidence that they were not plantigrade in the sense in which the feet of existing reptiles are plantigrade. I throw upon the screen a diagram showing the proximal ends of the metacarpal and metarsal [sic] elements (Fig. 19). they arrange themselves in a semicircle both in the hind foot and fore foot. This is less marked in the hind foot than in the fore foot.

Fig. 19. Diagram showing arrangement at proximal end. 1, of metacarpals; 2, of metatarsals of Diplodocus.

Such an arrangement of the metacarpals and metatarsals is significant, as has been pointed out by Hatcher and Osborn and is clearly shown by Abel. Sternfeld brushes Abel's criticism to one side, stating that it can be easily got rid of because the same arrangement exists in the feet of animals which are plantigrade. I would recommend Dr. Richard Sternfeld to more carefully study the anatomy of plantigrades. The structure of the feet of the sauropod dinosaurs differs immensely from that of the feet of all the recent reptilia. We have evidence of a rather conclusive character as to the fact that the sauropod dinosaurs were decidedly digitigrade in the one existing specimen of a sauropod footprint, which is happily preserved, a figure of which I throw upon the screen (Fig. 20). You will see as you examine it that the animal must have been provided, as Professor Hatcher long ago pointed out, with a very large foot-pad, and that its track is not at all like the track of any of the recent lacertilia. The evidence of this footprint is impressive and ought to go a long way toward confirming the view, which I believe is the only view which we can maintain, that these animals were more or less digitigrade in the pose of the foot.

Fig. 20. Footprint of sauropod dinosaur. Specimen in the Carnegie Museum.

The form of the limbs, long, straight, and pillar-like, in this respect differing vastly from the limbs of the creeping lacertilia and crocodilia, suggests that they were intended to support a weight thrown upon them from above. The femur of the crocodile, as you know, is bent, and the femora of many of the recent lacertilians likewise show a distinct curvature of the axis. The same thing is true of the fore limbs, notably in Varanus. The axis of the proximal end of the humerus in Varanus lies in a plane differing as much as forty-five degrees from the plane of the axis at the distal end. This is not true in the case of the sauropod dinosaurs. The limbs were intended to bear a burden placed mainly above, and their structure seems to plainly indicate this. It is in short impossible to articulate the limbs in such a position as to impart to the animal a crawling attitude. We have experimented a score of times and have tried different poses, only to come back again to the position which we have given to the reproduction of Diplodocus and which is the position that has generally been accepted by osteologists as the correct position for such animals when standing or moving forward. Our reproductions may be, as they have been contemptuously styled by Hay, "light-legged and straight-legged," but no one who has had the matter practically in hand has yet been able to suggest any way of escaping the conclusion that these creatures were at all events more or less "straight-legged." For their "light-legged" qualities nature is solely responsible, though I fail, standing before these huge bones, to see why anybody should so describe them. Students of the lacertilia and of the testudinata may sneer, but it is beyond possibility to adopt the suggestions which they from time to time make, that those of us who are engaged in studing [sic] the dinosaurs shall squeeze these creatures into the forms with which they are familiar. The critics possibly do not realize that weeks and months and years of study have been spent by those who have been charged with the task of assmebling these remains, and that the prescriptions, which they now furnish, have been already tried without their suggestion, and have for good reasons been found wanting. It is easy for a knight of the quill, who has never practically attended to the matter, to find fault. The latest attack upon those who have been making a special study of the sauropod dinosaurs has only served in the mind of the speaker to prove the correctness of the careful work which has been done in the past by students on both sides of the Atlantic. Evolution has had something to do since the sauropod dinosaurs walked the earth, and to say simply because the lacertilia of the present day creep and crawl that in Mesozoic times there were no reptiles which walked, is to go further than the facts seem to warrant. The pinnipedia and the cetacea live in the waters: it does not necessarily follow that their ancestors were aquatic in their habits and that their limbs were like those which they possess. Because a Varanus crawls to-day it does not necessarily follow that a sauropod dinosaur crawled. There is every evidence that they did not crawl, but that the restorations of Marsh, Osborn, and others are substantially correct in many important particulars. It is "a far cry" from the crocodilia, which, by the by, existed contemporaneously with the sauropoda, and the genera Brontosaurus, Morosaurus, and Diplodocus.

The Tornierian hypothesis may be dismissed, I think, as not within the range of the possible. It has, as one of my learned paleontological friends in Europe jocosely remarked to me, "only this feature to recommend it, that it accounts for the speedy disappearance of the sauropoda, because if true, their lives must have been spent in indescribable agony, every joint being dislocated."

Both Dr. Hay and Professor Tornier indulge in speculation as to the food of Diplodocus. Tornier emphatically repudiates the idea that the animal was herbivorous and suggests that it was piscivorous. Sternfeld pictures it as squatting on the banks of streams and feeding on snails, bivalves, and amphibians. Hay approves of the suggestion of the present speaker, that Diplodocus may have fed upon algæ. In this field we are all more or less left to our imaginations, and one man's guess is as good as another's. In view of the fact that cycads were numerous at the time when the Diplodocus and its allies lived and died, it may not be improper to renew the suggestion that possibly these plants furnished the food of the sauropod dinosaurs. However the terminal buds would have been poor fodder, being wooly and harsh, and the leaves are as stiff as wires and could not have been masticated by such teeth as the Diplodocus possessed. On the other hand the interior of the stems of the cycads, "sago-palms," is in all recent species a veritable mine of nutritious food, and was presumably the same in the ancestral forms. While the comparatively feeble dentition of the Sauropoda would not have been of much use in getting at these supplies of starchy food, the heavy claw-like armature of the feet was quite equal to the task of ripping open the thin outer bark of the stems, and this accomplished, a single cycad stem of some of the larger species would have furnished a good meal of soft food capable of satisfying the hunger even of a Diplodocus. This suggestion has been freely discussed by the speaker with Dr. N. L. Britton of the New York Botanical Garden, and seems plausible. It is thrown out as a hint worthy of consideration. If the terminal end of a cycad could have been torn away this also would have given access to the mass of food in the stem. The feeble dentition hardly seems equal to the task of tearing away this upper growth, but if it was, we then might have a reason for the great elongation of the neck.

Before I conclude these remarks I desire to say that I am not without hope that recent discoveries made by the Carnegie Institute will tend to throw a flood of light on the whole subject. We have found what paleontologists have been searching for for forty or fifty years, three skeletons of sauropod dinosaurs lying articulated where they died. They are imbedded in hard sandstone, the work of removing which from the bones must involve a vast expenditure of time and effort; but in one case at least we know already that the vertebral column lies in position, articulated from end to end. Apparently hardly any disturbance has occurred and the bones even to the minutest tuberosities and rugosities are as perfect as when the animal died. The sternal ribs are present. When we succeed in carefully working out these huge skeletons from the surrounding matrix we shall probably be able to clear up some of the disputed points in the osteology of the sauropod dinosaurs.