I know some of you must be thinking “What the hell? That’s not funny.” Well, maybe it isn’t,
but I tried my best *runs off and sobs quietly* but I thought I would use an lolcat as an intro to a little paleontology lesson. Maybe this picture will help make some sense out of things;
Taken from “Integument of the iguanodont dinosaur Trachodon“, Memoirs of the AMNH ; new ser., v. 1, pt. 1-2.
If you visit the American Museum of Natural History’s fourth floor, look carefully around the mounted Anatotitan bones; near the looming, tail-dragging skeletons should be a case revealing the remains of a “mummy” dinosaur, the one pictured above. This important fossil was discovered by George Sternberg (son of Charles Sternberg, who accompanied his son on this trip and oversaw the excavation) in 1908 in Converse County, Wyoming. Osborn’s paper, however, notes an even earlier discovery of such skin impressions from a hadrosaur;
First among these integument specimens to be discovered was the famous type of Trachodon mirabilis Cope (Amer. Mus. No. 5730), found by Dr. J. L. Wortman in 1884 and now mounted in the American Museum of Natural History as part of the Cope Collection. This animal is said by Dr. Wortman to have been surrounded by a natural cast of its epidermal impressions, which unfortunately were largely destroyed or lost in the removal of the skeleton from its surroundings. There are only three patches of epidermis remaining from the tail of this specimen.
At the time both Cope’s specimen and Sternberg’s specimen were attributed to the genus Trachodon, but Trachodon is no longer accepted as valid today, but whether the fossils we’re talking about here should be called Anatotitan or Edmontosaurus still seems to be debatable. The Wikipedia entry for Anatotitan sums things up fairly well in its “Taxonomic History” section for this dinosaur, a more in-depth discussion needing a full blog post of its own. For our purposes here, however, I will be calling the dinosaur Anatotitan as that is what the AMNH (where the specimen in question is housed) has deemed fit to call it.
In any event, the “integument” of this specimen (unlike Wortman’s) was carefully preserved by the Sternbergs, allowing scientists to get a detailed look at what the skin of this particular dinosaur looked like in places. While the “tubercles” (or scale-like structures) of this fossil are certainly of interest (I suggest you take a look at the paper and its many photographs/plates for yourself), what most interested me was Osborn’s discussion of the hand of Anatotitan. In the section “Epidermal Sheathing of the Manus,” Osborn describes how the forelimbs of Anatotitan were found encased in a kind of sheath or mitt, which Osborn also mentions preserved the digits were apparently “connected by an integumentary web which was developed even more prominently than in the swimming birds.” This seemed to fit in with the contemporary hypothesis that at least some hadrosaurs were primarily aquatic, and Osborn writes;
The presence of the broad marginal web of the manus and absence of enlarged tubercles either on the dorsal or ventral surface certainly tends to support the theory of a swimming rather than of a walking, or terrestrial function of the fore paddle.
The “mitt” of Anatotitan. Taken from “Integument of the iguanodont dinosaur Trachodon“, Memoirs of the AMNH ; new ser., v. 1, pt. 1-2.
Indeed, because the forelimbs didn’t seem to seem to show a coarser or denser skin covering (and because they were held together in a “web”), it was assumed that such a limb would not work well on land and therefore it must have been an adaptation for life in the water, perfectly consistent with the image of hadrosaurs already in mind. Indeed, the “web” between the fingers was really no such thing, being that webbing exists between the toes of modern birds, not as an enclosing mitten. If the forelimbs really were paddles, we would also have to wonder why the back legs were not equipped with webbing or some other structure to enlarge their surface area during a stroke, especially being that they would be much more powerful and important for swimming. This is all easy for me to say nearly 100 years after this paper was published however, being that I have available to me much more information than Osborn did when he wrote the paper. The superficially “duck-like” appearance of hadrosaurs is hard to overcome, however, and many are still shown slogging through swamps in relatively recent works of paleo-art. For a much more in-depth discussion of hadrosaurs and what their skeletons tell us about their habitats, I heartily recommend Bob Bakker’s The Dinosaur Heresies.