Megalonyx jeffersonii
Encyclopedia
Megalonyx jeffersonii, or Jefferson's ground sloth, is an extinct species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of giant ground sloth that lived from the Illinoian Stage during the Middle Pleistocene
Middle Pleistocene
The Middle Pleistocene, more specifically referred to as the Ionian stage, is a period of geologic time from ca. 781 to 126 thousand years ago....

 (150,000 years BP
Before Present
Before Present years is a time scale used in archaeology, geology, and other scientific disciplines to specify when events in the past occurred. Because the "present" time changes, standard practice is to use AD 1950 as the origin of the age scale, reflecting the fact that radiocarbon...

) through to the Rancholabrean
Rancholabrean
The Rancholabrean North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from less than 240,000 years to 11,000 years BP, a period of . It is usually considered to overlap the Middle Pleistocene...

 of the Late Pleistocene
Late Pleistocene
The Late Pleistocene is a stage of the Pleistocene Epoch. The beginning of the stage is defined by the base of the Eemian interglacial phase before the final glacial episode of the Pleistocene 126,000 ± 5,000 years ago. The end of the stage is defined exactly at 10,000 Carbon-14 years BP...

 (10,000 BC). Its closest living relatives are the two-toed tree sloths
Two-toed sloth
Choloepus is a genus of mammals of Central and South America, within the family Megalonychidae consisting of two-toed sloths. There are only two species of Choloepus : Linnaeus's Two-toed Sloth and Hoffmann's Two-toed Sloth...

 of the genus Choloepus.

This species ranged widely in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

. It belongs to the genus Megalonyx
Megalonyx
Megalonyx is an extinct genus of giant ground sloths of the family Megalonychidae endemic to North America from the Hemphillian of the Late Miocene through to the Rancholabrean of the Pleistocene, living from ~10.3 Mya—11,000 years ago, existing for approximately .-Taxonomy:The generic name...

, a name proposed by Thomas Jefferson
Thomas Jefferson
Thomas Jefferson was the principal author of the United States Declaration of Independence and the Statute of Virginia for Religious Freedom , the third President of the United States and founder of the University of Virginia...

, future president of the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, in 1797. (Jefferson's surname was appended to the animal as the specific epithet in 1822 by the French zoologist Anselme Gaëtan Desmarest
Anselme Gaëtan Desmarest
Anselme Gaëtan Desmarest was a French zoologist and author. He was the son of Nicolas Desmarest and father of Anselme Sébastien Léon Desmarest...

.)

Description

M. jeffersonii was a large, heavily built animal about 8 to 10 feet (2.5–3 m) long. Its maximum weight may have been as much as 800 pounds (360 kg). This is medium-sized among the giant ground sloths. Like other ground sloths it had a blunt snout, massive jaw, and large peg-like teeth. The hind limbs were plantigrade
Plantigrade
right|151px|thumb|Human skeleton, showing plantigrade habitIn terrestrial animals, plantigrade locomotion means walking with the podials and metatarsals flat on the ground. It is one of three forms of locomotion adopted by mammals...

 (flat-footed) and this, along with its stout tail, allowed it to rear up into a semi-erect position to feed on tree leaves. The forelimbs had three highly developed claws that were probably used to strip leaves and tear off branches.

Range

M. jeffersonii was apparently the most wide ranging giant ground sloth. Fossils are known from many Pleistocene sites in the United States, including most of the states east of the Rocky Mountains
Rocky Mountains
The Rocky Mountains are a major mountain range in western North America. The Rocky Mountains stretch more than from the northernmost part of British Columbia, in western Canada, to New Mexico, in the southwestern United States...

 as well as along the west coast. It was the only ground sloth to range as far north as the present-day Yukon
Yukon
Yukon is the westernmost and smallest of Canada's three federal territories. It was named after the Yukon River. The word Yukon means "Great River" in Gwich’in....

 and Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...

.

In the fall of 2010, the first specimen ever found in Colorado was discovered at the Ziegler Reservoir site near Snowmass Village (In the Rocky Mountains at an elevation of 8,874 feet).

Jefferson's "Certain Bones"

In 1796, Colonel John Stuart sent Thomas Jefferson
Thomas Jefferson
Thomas Jefferson was the principal author of the United States Declaration of Independence and the Statute of Virginia for Religious Freedom , the third President of the United States and founder of the University of Virginia...

 some fossil bones (a femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...

 fragment, ulna
Ulna
The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form and runs parallel to the radius, which is shorter and smaller. In anatomical position The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form...

, radius
Radius
In classical geometry, a radius of a circle or sphere is any line segment from its center to its perimeter. By extension, the radius of a circle or sphere is the length of any such segment, which is half the diameter. If the object does not have an obvious center, the term may refer to its...

, and some foot bones including three large claws) from a cave in Greenbrier County, Virginia (present-day West Virginia
West Virginia
West Virginia is a state in the Appalachian and Southeastern regions of the United States, bordered by Virginia to the southeast, Kentucky to the southwest, Ohio to the northwest, Pennsylvania to the northeast and Maryland to the east...

). In 1797, Jefferson (who was serving at the time as Vice President
Vice President of the United States
The Vice President of the United States is the holder of a public office created by the United States Constitution. The Vice President, together with the President of the United States, is indirectly elected by the people, through the Electoral College, to a four-year term...

) presented a paper on "Certain Bones" to the American Philosophical Society
American Philosophical Society
The American Philosophical Society, founded in 1743, and located in Philadelphia, Pa., is an eminent scholarly organization of international reputation, that promotes useful knowledge in the sciences and humanities through excellence in scholarly research, professional meetings, publications,...

 in Philadelphia. He theorized that they were the remains of a lion
Lion
The lion is one of the four big cats in the genus Panthera, and a member of the family Felidae. With some males exceeding 250 kg in weight, it is the second-largest living cat after the tiger...

 which he named Megalonyx ("giant claw"). Jefferson believed that this lion was still alive (the species was extant), which is of particular importance because the validity of his argument would directly be used in the argument for or against evolution. Jefferson believed in a "completeness of nature" worldview which contrasted the new theory of evolution, where no species have or ever will go extinct naturally. When Lewis and Clark embarked on their expedition (1804–1806), he asked them to keep an eye out for this "Megalonyx", as he insisted this species was still in existence. If the creature was found, he could use this to support his argument against the concept of the extinction
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...

 of species. His argument, of course, was later not supported by the scientific community and shown to be incorrect.
Jefferson is considered to have initiated the science of vertebrate paleontology
Vertebrate paleontology
Vertebrate paleontology is a large subfield to paleontology seeking to discover the behavior, reproduction and appearance of extinct animals with vertebrae or a notochord, through the study of their fossilized remains...

 in the United States with the reading of this paper. In 1799, Dr. Caspar Wistar
Caspar Wistar (physician)
Caspar Wistar was an American physician and anatomist. He is sometimes referred to as Caspar Wistar the Younger, to distinguish him from his grandfather of the same name.-Biography:...

 correctly identified the remains as belonging to a giant ground sloth. In 1822, Wistar proposed naming it Megalonyx jeffersonii in honor of the former president. Desmarest then published it as such.

Which cave?

For many decades, Jefferson's "Certain Bones" had been assumed to have come from Organ Cave
Organ Cave
Organ Cave is a large and historic cave in Greenbrier County, West Virginia, USA. The surrounding community takes its name from the cave.In November 1973, the Organ Cave System — also known as the Organ-Hendricks Cave System — was registered as a National Natural Landmark for being "the largest...

 in what is now Greenbrier County, West Virginia
Greenbrier County, West Virginia
As of the census of 2000, there were 34,453 people, 14,571 households, and 9,922 families residing in the county. The population density was 34 people per square mile . There were 17,644 housing units at an average density of 17 per square mile...

. This theory originated in the early 20th century when a local man, Andrew Price of Marlinton
Marlinton, West Virginia
Marlinton is a town in Pocahontas County, West Virginia, United States. The population was 1,204 at the 2000 census. It is the county seat of Pocahontas County.-History:...

, decided this and popularized the idea.In 1993, two fragments of a Megalonyx scapula
Scapula
In anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle ....

 were found in Haynes Cave
Haynes Cave
Haynes Cave is a cave within the Greenbrier River watershed in West Virginia. It sits within the complex hydrology of the historic Second Creek watershed in Monroe County....

 in neighboring Monroe County
Monroe County, West Virginia
As of the census of 2000, there were 14,583 people, 5,447 households, and 3,883 families residing in the county. The population density was 31 people per square mile . There were 7,267 housing units at an average density of 15 per square mile...

. In 1995, Smithsonian paleontologist Frederick Grady proposed that Haynes Cave was the true original source of Jefferson's fossil.

Grady’s reasons had to do with historical land-ownership records. Jefferson reported that the bones had been found by saltpeter
Potassium nitrate
Potassium nitrate is a chemical compound with the formula KNO3. It is an ionic salt of potassium ions K+ and nitrate ions NO3−.It occurs as a mineral niter and is a natural solid source of nitrogen. Its common names include saltpetre , from medieval Latin sal petræ: "stone salt" or possibly "Salt...

 workers and gave the cave owner’s name as Frederic Crower, an apparent misspelling (according to Grady) of Frederic Gromer. Correspondence between Jefferson and Colonel Stuart, who sent him the bones, indicates that the cave was about five miles from Stuart’s home and contained saltpeter vats. Grady believes that Organ Cave can be eliminated as the source cave as it was never owned by Gromer. In addition, two letters written by the subsequent owner of the cave—Tristram Patton—indicate that the cave was in Monroe County
Monroe County, West Virginia
As of the census of 2000, there were 14,583 people, 5,447 households, and 3,883 families residing in the county. The population density was 31 people per square mile . There were 7,267 housing units at an average density of 15 per square mile...

 near Second Creek. (Monroe County, originally part of Greenbrier County, was separated shortly after the discovery of the bones.) In the letters, Patton described the cave and indicated that more bones were there.

M. jeffersonii is still the most commonly identified species of Megalonyx. It was designated the state fossil of West Virginia
West Virginia
West Virginia is a state in the Appalachian and Southeastern regions of the United States, bordered by Virginia to the southeast, Kentucky to the southwest, Ohio to the northwest, Pennsylvania to the northeast and Maryland to the east...

 in 2008.

In popular culture

  • Sid, a character in the Ice Age movies
    Ice Age (film series)
    Ice Age is a series of animated films produced by Blue Sky Studios, a division of 20th Century Fox, and featuring the voices of Ray Romano, John Leguizamo, Denis Leary, and Chris Wedge. Three films have been released in the series thus far, Ice Age in 2002, Ice Age: The Meltdown in 2006, and Ice...

    , is supposed to be a Jefferson's ground sloth, but is much weaker and smaller than the real Jefferson's ground sloth really was, and he can climb trees, which Jefferson's ground sloths weren't good at doing.
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