Case 004: The President's Impossible Beast

Exhibit A · Folio 1 of 5

The Evidence

In 1796, workmen digging saltpeter in a cave in Greenbrier County, Virginia (today West Virginia) struck bone. Not deer bone, not bear bone. Among the finds: enormous curved claws, the largest close to eight inches long, attached to forelimb bones of absurd proportion.

Colonel John Stuart, a local landowner who knew exactly one person in America who would lose his mind over this, crated the bones and sent them to Thomas Jefferson, who was at that moment in the middle of becoming Vice President of the United States.

Specimen plate: three enormous curved fossil claws recovered from the Greenbrier saltpeter cave, the largest nearly eight inches long — Exhibit AClaws recovered from the saltpeter cave

Exhibit B · Folio 2 of 5

The Theory

Jefferson studied the claws and reached for the most reasonable explanation available to an eighteenth-century mind: a cat. A very, very large cat. He named the creature Megalonyx, Greek for "Great Claw," and reckoned it a lion-like predator more than three times the size of the African lion.

In March 1797, days before being sworn in as Vice President, he arrived in Philadelphia carrying both his inauguration and a box of monster bones, and presented his memoir on the Great Claw to the American Philosophical Society. Priorities, in other words, fully in order.

★ American Oddity

Jefferson's paper on Megalonyx was, in effect, homework turned in by a sitting Vice President. It helped found American vertebrate paleontology, a science set in motion by a statesman who never stopped being a naturalist.

Comparative scale diagram: a standing man and an African lion beside the dashed red outline of Jefferson's imagined giant Megalonyx, more than three times the lion's size — Exhibit BThe suspect, reconstructed from the evidence of 1797

Exhibit C · Folio 3 of 5

The Conviction

Here is the part that turns a fossil story into an American one: Jefferson did not believe the beast was gone. Extinction, to him, implied a broken world, and he had already argued, in Notes on the State of Virginia, that nature does not misplace her creations.

"Such is the economy of nature, that no instance can be produced, of her having permitted any one race of her animals to become extinct." — Thomas Jefferson, Notes on the State of Virginia

So when American explorers later headed west, the instructions carried a quiet hope stranger than fiction: keep an eye out. Somewhere past the Mississippi, the thinking went, the mammoth and the Great Claw might still be walking around.

Exhibit D · Folio 4 of 5

The Verdict

The correction came from anatomy, not adventure. Dr. Caspar Wistar of Philadelphia examined the bones and recognized what the claws actually were: not the weapons of a super-lion, but the digging and hooking claws of a giant ground sloth, a slow plant-eating colossus the size of an ox.

In 1822, science paid its respects. The species was formally named Megalonyx jeffersonii, Jefferson's Great Claw, honoring the man whose memoir first brought the bones into the scientific record.

★ Case Closed?

Megalonyx jeffersonii stood about three meters tall on its hind legs, weighed as much as a small car, and went extinct roughly 11,000 years ago. It is today the official state fossil of West Virginia, the very ground it was pulled from.

The imagined lion as a faded dashed outline beside the true animal: the giant ground sloth Megalonyx jeffersonii, fully drawn, walking on the knuckles of its great claws — Exhibit DImagined predator vs. actual vegetarian

Exhibit E · Folio 5 of 5

The Legacy

Jefferson got the animal wrong and the moment right. His memoir, published in the Society's Transactions in 1799, is a founding document of American vertebrate paleontology: evidence collected, measured, described, argued over, and corrected in public. Being magnificently wrong, carefully and on the record, is how the science got started.

That is the spirit this case file celebrates: a country curious enough to mail monster bones to its Vice President, and a Vice President curious enough to write them up.

The Full Record

Thomas Jefferson, Megalonyx, and the Birth of American Paleontology

In 1796, laborers digging saltpeter deposits in a limestone cave in Greenbrier County, Virginia (in present-day West Virginia), uncovered a set of unusually large fossil bones, including forelimb elements and claws measuring up to about eight inches (20 cm). Colonel John Stuart forwarded the specimens to Thomas Jefferson, then Vice President–elect of the United States and one of the country's most prominent natural philosophers.

Jefferson's "Great Claw" (1797)

Jefferson concluded that the bones belonged to an enormous predator of the cat family, which he named Megalonyx, from the Greek for "great claw." By comparing the claw dimensions with those of the African lion, he estimated the animal at more than three times the lion's size. He presented his findings to the American Philosophical Society in Philadelphia in March 1797, the same month he was inaugurated as Vice President, and his "Memoir on the Discovery of Certain Bones of a Quadruped of the Clawed Kind in the Western Parts of Virginia" was published in the Society's Transactions in 1799.

Jefferson and the problem of extinction

Jefferson was famously reluctant to accept the concept of extinction. In Notes on the State of Virginia he argued that the "economy of nature" offered no example of a species being permitted to die out. Consistent with this view, he considered it possible that both the mammoth and Megalonyx survived in the unexplored American interior, and western expeditions of the era, including Lewis and Clark's, were encouraged to look for evidence of such animals.

Wistar's correction and the naming of the species

The Philadelphia physician and anatomist Caspar Wistar examined the Greenbrier bones and recognized their affinity with the giant ground sloths, publishing a careful anatomical description in 1799. The animal was not a predator but a large herbivore related to the South American Megatherium. In 1822, the species was formally named Megalonyx jeffersonii in Jefferson's honor. Adult individuals reached roughly three meters (10 feet) in length and are estimated to have weighed around 800–1,000 kilograms. The species ranged widely across North America before its extinction near the end of the Pleistocene, roughly 11,000 years ago.

Why this case matters

Jefferson's memoir is widely regarded as a founding episode of vertebrate paleontology in the United States: fossil material was collected, measured, compared, publicly presented and, crucially, publicly corrected. Megalonyx jeffersonii was designated the official state fossil of West Virginia in 2008, returning the honor to the ground it came from.

Sources & further reading

Jefferson, T. (1799). "A Memoir on the Discovery of Certain Bones of a Quadruped of the Clawed Kind in the Western Parts of Virginia." Transactions of the American Philosophical Society, Vol. 4.
Wistar, C. (1799). "A Description of the Bones Deposited, by the President, in the Museum of the Society." Transactions of the American Philosophical Society, Vol. 4.
Jefferson, T. (1785). Notes on the State of Virginia, Query VI.
American Philosophical Society: archives on Jefferson's fossil collections.
West Virginia Legislature (2008): designation of Megalonyx jeffersonii as state fossil.

The President's Impossible Beast