Laelaps

Last week I looked at reconstructions of Diplodocus (both humorous and scientific) by Oliver Hay and G.G. Simpson. After rifling through my collection of papers, I came upon a description of Diplodocus by H.F. Osborn and thought I would continue the trend I had set earlier.

In 1897, the AMNH sent a field crew to look over the famous Como Bluff quarries that were so productive for O.C. Marsh in previous years, and although the site was considered exhausted Barnum Brown quickly came across a Diplodocus femur. There was more than just a femur, however, and soon J.L. Wortmann was supervising the excavation of the skeleton the femur had led the team to. Unfortunately the remains were not as complete as was originally hoped, but in the end the team was able to recover the hips, most of the tail, a portion of the vertebral column leading up to the tail, a femur, and a few ribs, all of which were shipped back to New York for study.

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The portions of Diplodocus recovered by the AMNH team in 1897. From Osborn 1899.

According to Osborn’s paper, the material recovered in 1897 provided a much more complete picture of the back-end of Diplodocus than was previously grasped. First, Osborn felt there was a certain balance between the vertebrae immediately in front of and behind the sacrals (fused vertebrae between the hips). This led him to infer that Diplodocus could have used its tail as a tripod, “certainly while in the water, and quite possibly
while on land.” (This idea was later brought to life in an illustration by Charles R. Knight and is strikingly reproduced in the rearing Barosaurus that greets visitors entering the AMNH today.) Overall, though, Osborn admired the way the vertebral column maximized strength while minimizing weight, causing him to declare;

The ingenuity of sculpture by which this is brought about, every single vertebra differing from its fellow, baffles the Lamarckian as well as the Darwinian, and tempts us to revive the old teleological explanation.

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Knight’s standing Diplodocus (1907). The reconstruction of the standing Barosaurus in the Grand Rotunda of the American Museum of Natural History is surprisingly similar to this painting.

After cataloging the characters of the vertebral column and other bones, Osborn provides a restoration of the habits of the animal, although he admits that any reconstructions are going to be subject to change until the neck and limbs of Diplodocus would be found and better understood. Still, the bones at Osborn’s disposal seemed to be from a lighter, yet longer animal that “Brontosaurus,” and the most telling part of the available skeleton was the tail.

As mentioned in my summary of Hay’s paper, sauropods were generally thought to be bound to water, especially since the geology and other fossils where sauropod specimens were found appeared to be indicative of a freshwater lake or swamp environment. The fact that Diplodocus had a tail about half the length of the body based upon Osborn’s calculations suggested to him that the tail was used to propel the dinosaur through the water. What else could such a huge tail be for?

Diplodocus gives us a new and different conception of the Cetiosaurs or Sauropoda, one which increases their ability as aquatic reptiles, and specializes the functions of the tail. The tail constituted one half the length of the animal, and was of imnmense service as a propeller in enabling it to swim rapidly through the water, the broad anterior portion being provided with very powerful lateral muscles, and the compressed posterior portion being controlled by tendons and made effective by a vertical fin.

Again, the construction of the tail suggested to Osborn that the animal could (and often did) rear up, using its long tail like a tripod, although the reason why this might be so is left obscure. Diplodocus was no sluggard like “Brontosaurus,” though. The lighter construction of the skeleton led Osborn to infer it had a much more active lifestyle in his conclusion;

…the animal was capable not only of powerful but of very rapid movements. In contrast with Brotosaurus it was essentially long and light-limbed and agile. Its tail was a means of defence upon land and a means of rapid escape by water from its numerous carnivorous foes. Its food probably consisted of some very large and nutritious species of water-plant. The anterior claws may have been used-in uprooting such plants, while the delicate anterior teeth were employed for prehensile purposes only. The plants may have been drawn down the throat in large quantities without mastication, since there were no grinding teeth whatever. It is only by some such means as these that these enormous animals could have obtained sufficient food to support their great bulk.

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The pelvis of Diplodocus recovered by the AMNH team. It is still on display on the fourth floor of the AMNH, tucked away near the gift shop.

Ultimately Osborn’s reconstruction of Diplodocus seems to have been forgotten. The presence of a fin on the distal end of the tail and the idea of the dinosaur digging for soft plants with its front limbs were subject to ridicule by other scientists (see my summary of Hay’s paper), and the discovery of more complete specimens did away for the need to speculate on what the rest of the animal might be like. Although it would eventually be removed from the swamps as paleontology itself evolved, Osborn’s idea of an active Diplodocus would have to wait for the “Dinosaur Renaissance.”

References;

Osborn, H.F. (1899) “A Skeleton of Diplodocus.” Memoirs of the American Museum of Natural History, Vol. 1 (5), pp. 191 – 214