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 Two

Fig. 12. Reproduction of figures given by Tornier showing the restoration of scapula and fore limb of Diplodocus.

Dr. Tornier labors long with the scapula and the humerus. As I have already stated, he claims that the humerus of Diplodocus is startlingly—"verblüffend"—like that of Varanus. It is wonderful what a man can see who has determined to see things! If you will simply take the trouble to compare the humerus of the sauropod dinosaurs with that of a Varanus I think you will be able without opening your eyes very widely to discover a number of startling differences. In addition to falling into error as to the startling likeness existing between the humerus in the sauropoda and the lacertilia, he makes a multitude of grossly inaccurate and misleading statements in uttering the special plea which he makes for his theory. It would be wearisome to recall them. One of the more noticeable misstatements is made when he declares that the coracoid bone belongs on the lower side of the belly&madsh;"Bauchunterseite." The coracoid, as we all know, is a sternal element and has nothing whatever to do with the "Bauch," or belly. He ignores the fact that the superior surfaces of the anterior ribs and the lateral processes of the anterior dorsal vertebræ unite to form a surface evidently adapted to the end of providing a field over which the long dorsal blade of the scapula can play. He demands for the scapula a vertical position so as to give to the humerus an opportunity, as he says, to move in a horizontal plane backward and forward. He states that a vertical position of the scapula is universal among recent reptilia, which is not the case. It is true of the lacertilia, but it is not true of the crocodilia. I herewith give a reproduction of a drawing copied from Blainville of a crocodilian skeleton, and another copied from Brühl (Fig. 13), both of which show that the scapula in the crocodile has a position in the articulated skeleton similar to that which it has in the mammalia.

Fig. 13. 1, the skeleton of an alligator after Blainville; 2, skeleton of crocodile after Brühl, showing position of the scapula.

But lest some one may say that the artists were mistaken, I am able through the kindness of Dr. Geo. C. Johnston, of Pittsburgh, the well-known radiographer, to exhibit a number of X-ray photographs showing the scapula in position in the common American alligator (Fig. 14).²

Fig. 14. X-ray photograph of scapula and humerous of alligator in position with foot thrown backward as far as possible. (Photographed by Dr. Geo. C. Johnston, Pittsburgh, Pa.) The scapula is not vertical.

These photographs show the entire accuracy of the drawings by Blainville and Brühl. And I am prepared to further verify the drawings by an example of an alligator in the flesh, in which the parts surrounding the scapula have been dissected away, showing the scapula in the same position which is given by Blainville and Brühl. Any one who cares to verify the accuracy of my statements can easily do so. The scapula in the crocodile does not lie in the position which is given to the scapula by Mr. Tornier in his restoration and it certainly did not so lie in the Diplodocus, but the lateral processes of the anterior dorsal vertebræ and the proximal ends of the anterior ribs will see that there is here provided by nature a plane adapted to the inner surface of the scapula.

For the sake of experiment I have placed the scapula in the position demanded for it by Mr. Tornier, and have swung the forelimbs into place as he demands that they shall be put (Fig. 15).

Fig. 15. 1, rear view of scapula and fore limb of Diplodocus mounted according to the Tornierian prescription; 2, side view of ditto.

The result is in every way amusing. It leads in the first place to the entire disarticulation of the humerus from the radius and ulna. But as a secondary consequence it leads to a rather remarkable result, which the Berlin critic did not think o. In the position which Professor Tornier demands for the elements of the fore limb, the foot must fall into a position with the toes turned inwardly, while put into the position which he demands for the hind limbs the toes of the latter necessarily point outwardly. The accompanying diagram (Fig. 16) shows you the position which the hind feet and forefeet assume when placed as Professor Tornier demands they shall be placed.

Fig. 16. Diagram showing position of the foot of Diplodocus when mounted and moved according to the Tornierian prescription.

Now, attributing to the humerus backward and forward motion in a horizontal plane, you will see, as the dotted lines in the diagram show, the result which is reached when the humerus is thrown into a line parallel with the line given to the femur. The toes of the manus point inward and backward. The animal was "pigeon-toed" in front, while its hind feet were planted like those of a grenadier. The animal moved forward with the hind feet, moved backward with its fore feet. If Tornier is right it must have necessarily have been somewhat "balled up."

The Berlin critic denies the possibility of a backward and forward movement of the humerus in the scapula in a vertical plane. As an actual fact, in the judgement of competent American investigators, the articulating surface of the humerus did thus move in the scapula, and the great projection on the outer side of the proximal end of the humerus, showing every evidence of having been provided with enormous muscular attachments, gave the animal the power to move the limb in the direction indicated, this projection being strictly analogous in function to the great trochanter of the humerus as it exists in the mammalia to-day. The statement that the downward projecting angle of the coracoid at its union with the scapula to form an acetabulum for the humerus preculded backward and forward motion in a perpendicular plane, as Tornier avers, is not borne out by an examination of the skeleton in situ. The humerus was capable of thus moving through a very long arc.

Professor Tornier utterly ignores in his discussion a very important point, and that is, the structure of the ribs of the Diplodocus as compared with the structure of these parts in the recent reptilia. I throw upon the screen for purposes of easy comparison views of the ribs as they are arranged in recent crawling reptiles and of the ribs as they exist in the sauropoda, and more particularly in Diplodocus (Fig. 17).

Fig. 17. Seventh dorsal rib articulated in 1, Uromastrix; 2, Varanus; 3, Iguana; 4, Crocodilus; 5, Diplodocus.

A glance at this diagram must be sufficient to show you the enormous differences which exist, and to reveal to one who has the least mechanical aptitude that the body, or "barrel," of the Diplodocus was constructed upon an ornithic rather than upon a lacertilian model. The articulation of the ribs does not lend itself to the idea that the animal progressed upon its belly.

Professor Tornier says that the long tail of the sauropod dinosaurs was intended to be carried at full length upon the ground, to stiffen and guide the movement of the anterior portion of the body. He speaks of it as intended for anchoring the body, describing it as "ein Verankerungsmittel." No doubt it did to a certain extent so function, but to regard it as having been an instrument for promoting, as Sternfeld indicates, a wriggling motion—"schlängelnde Bewegung"—is to attribute to the organ properties which it hardly possessed. The tail, while capable, no doubt, when the animal assumed a crouching position, of functioning as Tornier demands that it shall, must nevertheless have been to a very large degree used also as a support upon which the animal could when necessary prop itself, as upon one of the legs of a tripod, as undoubtedly was the case with the carnivorous dinosaurs, to which the sauropoda are not so very distantly related.

² At this point the lecturer threw upon the screen a number of projections from X-ray photographs showing the limbs of the alligator in different attitudes. Only one of these is reproduced in the text. Back

Dr. Holland's Opus continues in Part Four.