A Review of Some Recent Criticisms.

Sunday, September 4, 2011

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

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.

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.

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.

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