Discovering The Great Claw:
Part 2 - The Ground Sloth
An unexpected thing happened to Jefferson before he was to present the talk on Megalonyx (=Great Claw). He had been browsing a Philadelphia bookstore when he chanced upon an article in the British publication Monthly Magazine. It contained a short abstract and illustration based on a 1796 publication by Georges Cuvier on a giant, clawed fossil from Paraguay. The fossil, which was essentially a complete skeleton, belonged to an unknown animal that was clearly related to the South American tree sloths. Cuvier had named this creature Megatherium.
Confronted with the possibility that his "lion" may in fact be a relative of the sloth, Jefferson hastily appended a postscript to his talk. He acknowledged that Megalonyx could, in fact, be Megatherium . On the other hand, Jefferson was skeptical that the two were identical. He remarked that the magazine article's illustration "is not so done as to be relied on, and the account is only an abstract". Moreover, he commented, "having nothing of our animal but the leg and foot bones, we have few points for a comparison between them." Jefferson acknowledged that the limb bones resembled each other but he still reserved judgment. After all, Cuvier's identification of Megatherium as a relative of the sloth was based primarily on its teeth. Jefferson concluded:
"But to solve satisfactorily the question of identity, the discovery of fore-teeth, or of a jaw bone shewing it had, or had not, such teeth, must be waited for, and hoped with patience. I may be better in the mean time, to keep up the difference of name."
Jefferson's 1797 talk on the Great-Claw was published in the Transactions of the American Philosophical Society in 1799 (Volume 4). Later in that same volume, Caspar Wistar wrote about the Megalonyx bones Jefferson deposited at the society. Wistar, a physician by training and an excellent anatomist, provided detailed descriptions and illustrations of the fossils. He also concluded that the bones did not belong to a cat. Instead, he noted that they were similar in form to those of "bradypus" [Bradypus], the three-toed sloth (1), but they were many times larger. Wistar considered the illustration and short abstract of the 1796 Monthly Magazine article to be insufficient for a definitive conclusion as to whether Megatherium and Megalonyx were identical. On the other hand, if one accepted the magazine's illustration as reliable, then, Wistar concluded, Megalonyx and Megatherium must be two different species.
Jefferson abandoned his interpretation of Megalonyx as a giant cat sometime after he presented his talk at the American Philosophical Society. Instead, he concluded that it was probably identical to Cuvier's Megatherium. Nevertheless, he did not abandon his belief that the animal was still alive. In a 1803 letter to the French naturalist Bernard Lacépède, Jefferson wrote:
It is not improbable that this voyage of discovery [the Lewis and Clark expedition] will procure further information of the Mammoth [mastodon], & of the Megatherium [Megalonyx].
In a 1804 memoir on ground sloths Georges Cuvier concluded that Jefferon's animal and Megatherium were not identical and that both animals were now extinct. The French naturalist retained Jefferson's name for the animal, Megalonyx. In 1822, another French anatomist, Anselme Demarest, formerly described the fossil and named it Megalonyx jeffersonii in honor of the celebrated American. Joseph Leidy provided a detailed description of this ground sloth from nearly complete material in 1855. (See Leidy on Extinct Ground Sloths).
Jefferson's Megalonyx memoir is arguably the first American publication in paleontology. It was also the first and only paleontology paper written by Jefferson. Thereafter he willingly deferred to Caspar Wistar, whom Jefferson recognized as eminently more qualified. In 1807, Jefferson —then president of the United States— requested Wistar's expertise in evaluating a roomful of fossils collected by William Clark at Big Bone Lick (2).
Webpages:
- The Academy of Natural Sciences' web page on Joseph Leidy's study
of Megalonyx and other ground sloths:
www.ansp.org/museum/leidy/paleo/ground_sloths.php - American Philosophical Society:
www.amphilsoc.org
Print Resources:
- Bedini, S.A. 1985. Thomas Jefferson and American Vertebrate Paleontology. Virginia Division of Mineral Resources Publication 61. Charlottesville. 26 pp.
- Buffon, Georges Louis LeClerc, comte de. 1749-1788. Histoire naturelle, générale et particulière. Paris: Imprimeries royale.
- Cuvier, Geoges. 1796. "Notice sur le squelette d'une très-grande espèce de quadrupède onconnue jusqu'à présent, trouvé au Paraguay, et déposé au cabinet d'historie naturelle de Madrid, redigée par G. Cuvier". Magasin encyclopédique, 2e anée, 1: 303-310.
- Cuvier, Georges. 1804. "Sur le mégalonix, Animal de la famille des Paresseux, mais de la taille du Boeuf, dont les ossemens on été décourverts en Virginie, en 1796." Annales du Muséum National d'Histoire Naturelle, 5: 358-375.
- Cuvier, Georges. 1812. Researches sur les ossemens fossilses de quadrupèdes, où l'on rétablit les caractères de plusieurs espèces d'animaux que les révolutions du globe paroissent avoir détruites. 4 vol. Paris: Deterville.
- Desmarest, Anselme. 1822. Mammalogie ou description des espèces de mammifères. Seconde partie, contenant les ordres des rongeurs, des édentés, des pachydermes, des ruminans et des cétacés. M me Veuve Agasse, Paris, pp. i-viii, 277-556.
- Jefferson, T. 1799. "A Memoir of the Discovery of certain Bone of a Quadruped of the Clawed Kind in the Western Parts of Virginia." Transactions of the American Philosophical Society, Vol. 4, No. 30, pp. 246-260.
- Rudwick, M.J.S. 1997. Georges Cuvier, Fossil Bones and Geological Catastrophes: new translations. Chicago: University of Chicago Press.
- Semonin, P. 2002. American Monster: How the nation's first prehistoric creature became a symbol of national identity. New York & London: New York University Press.
- Wistar, Caspar. 1799. "A description of the Bones deposited by the President, in the Museum of the Society, and represented in the annexed plates." Transactions of the American Philosophical Society, Vol. 4, No. 71, pp. 526-531.
Notes:
- Although he was an excellent anatomist, Caspar Wistar didn't have access to the resources available to some European authorities. Lacking decent information about Megatherium but given Cuvier's conclusion that it was related to living sloths, Wistar compared Megalonyx with the South American three-toed sloth (Bradypus). Even here, however, he had to resort to Louis-Jean-Marie Daubenton's description of the sloth's foot as presented in Buffon's Histoire naturelle. [go back]
- See Discovery of the Mastodon: Part 8 - Fossils in the White House for more information. [go back]
Image Credits:
- The image of Caspar Wistar courtesy of Smithsonian Institution Libraries' Scientific Identity website: [go back]
www.sil.si.edu/digitalcollections/hst/ scientific-identity/intro.htm. - Leidy, Joseph. 1855. "A Memoir of the Extinct Sloth Tribe of North America." Smithsonian Contributions to Knowledge 7(5). [go back]