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''Megalonyx'' (
Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...
, "large claw") is an extinct
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of
ground sloth Ground sloths are a diverse group of extinct sloths in the mammalian superorder Xenarthra. The term is used to refer to all extinct sloths because of the large size of the earliest forms discovered, compared to existing tree sloths. The Caribbe ...
s of the
family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...
Megalonychidae Megalonychidae is an extinct family of sloths including the extinct ''Megalonyx''. Megalonychids first appeared in the early Oligocene, about 35 million years (Ma) ago, in southern Argentina (Patagonia). There is actually one possible find dating ...
, native to North America during the
Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...
epochs. It became extinct during the
Quaternary extinction event The Quaternary period (from 2.588 ± 0.005 million years ago to the present) has seen the extinctions of numerous predominantly megafaunal species, which have resulted in a collapse in faunal density and diversity and the extinction of key ecolog ...
at the end of the
Rancholabrean The Rancholabrean North American Land Mammal Age on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from less than 240,000 years to 11,000 years BP, a p ...
of the Pleistocene, living from ~5 million to 11,000 years ago. The
type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...
, ''M. jeffersonii'', measured about and weighed up to . ''Megalonyx'' is descended from ''
Pliometanastes ''Pliometanastes'' is an extinct genus of ground sloths of the family Megalonychidae endemic to North America during the Late Miocene epoch through very early Pliocene epoch ( Hemphillian in the NALMA classification). Its fossils have been foun ...
,'' a genus of ground sloth that had arrived in North America during the Late
Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...
, prior to the
Great American Biotic Interchange The Great American Biotic Interchange (commonly abbreviated as GABI), also known as the Great American Interchange and the Great American Faunal Interchange, was an important late Cenozoic paleozoogeographic biotic interchange event in which lan ...
. ''Megalonyx'' had the widest distribution of any North American ground sloth, having a range encompassing most of the contiguous United States, extending as far north as Alaska during warm periods.


Taxonomy

In 1796, Colonel John Stuart sent
Thomas Jefferson Thomas Jefferson (April 13, 1743 – July 4, 1826) was an American statesman, diplomat, lawyer, architect, philosopher, and Founding Fathers of the United States, Founding Father who served as the third president of the United States from 18 ...
, shortly before he took office as
Vice President of the United States The vice president of the United States (VPOTUS) is the second-highest officer in the executive branch of the U.S. federal government, after the president of the United States, and ranks first in the presidential line of succession. The vice ...
, some fossil bones: a
femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with ...
fragment,
ulna The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...
,
radius In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...
, and foot bones including three large claws. The discoveries were made in a cave in
Greenbrier County Greenbrier County () is a county in the U.S. state of West Virginia. As of the 2020 census, the population was 32,977. Its county seat is Lewisburg. The county was formed in 1778 from Botetourt and Montgomery counties in Virginia. History P ...
, Virginia (present-day
West Virginia West Virginia is a state in the Appalachian, Mid-Atlantic and Southeastern regions of the United States.The Census Bureau and the Association of American Geographers classify West Virginia as part of the Southern United States while the Bur ...
). Jefferson examined the bones and presented his observations in the paper "A Memoir on the Discovery of Certain Bones of a Quadruped of the Clawed Kind in the Western Parts of Virginia" to the
American Philosophical Society The American Philosophical Society (APS), founded in 1743 in Philadelphia, is a scholarly organization that promotes knowledge in the sciences and humanities through research, professional meetings, publications, library resources, and communit ...
in
Philadelphia Philadelphia, often called Philly, is the largest city in the Commonwealth of Pennsylvania, the sixth-largest city in the U.S., the second-largest city in both the Northeast megalopolis and Mid-Atlantic regions after New York City. Sinc ...
on March 10, 1797. In the paper, he named the then unknown animal ''Megalonyx'' ("giant claw") and compared each recovered bone to the corresponding bone in a
lion The lion (''Panthera leo'') is a large Felidae, cat of the genus ''Panthera'' native to Africa and India. It has a muscular, broad-chested body; short, rounded head; round ears; and a hairy tuft at the end of its tail. It is sexually dimorphi ...
. Jefferson did not attempt a definitive taxonomic classification and kept an open mind, writing “Let us only say then, what we may safely say, that he was more than three times as large as the lion”. In his postscript, Jefferson mentions the remains of a ''
Megatherium ''Megatherium'' ( ; from Greek () 'great' + () 'beast') is an extinct genus of ground sloths endemic to South America that lived from the Early Pliocene through the end of the Pleistocene. It is best known for the elephant-sized type species ' ...
'' discovered in Paraguay and notes its anatomical similarities to ''Megalonyx''. Contrary to the scientific consensus emerging at the time that
extinction Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually 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 ...
had played an important role in natural history, Jefferson believed in a "completeness of nature" whose inherent balance did not allow species to go extinct naturally. He asked
Lewis and Clark Lewis may refer to: Names * Lewis (given name), including a list of people with the given name * Lewis (surname), including a list of people with the surname Music * Lewis (musician), Canadian singer * "Lewis (Mistreated)", a song by Radiohead ...
, as they planned their famous expedition in 1804–1806, to keep an eye out for living specimens of ''Megalonyx'', as this would support his case. His idea made no headway and was later shown to be incorrect. His presentation to the American Philosophical Society in 1797 is often credited as the beginning of
vertebrate paleontology Vertebrate paleontology is the subfield of paleontology that seeks to discover, through the study of fossilized remains, the behavior, reproduction and appearance of extinct animals with vertebrae or a notochord. It also tries to connect, by us ...
in
North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
. In 1799,
Caspar Wistar Caspar Wistar may refer to: * Caspar Wistar (glassmaker) (1696–1752), Pennsylvania glassmaker and landowner * Caspar Wistar (physician) Caspar Wistar (September 13, 1761January 22, 1818) was an American physician and anatomist. He is sometim ...
correctly identified the remains as those of a giant ground sloth. In 1822, Wistar proposed naming the species ''Megalonyx jeffersonii'' in honor of the former statesman. Desmarest then published it as such. ''Megalonyx'' was first formally named by
Richard Harlan Richard Harlan (September 19, 1796 – September 30, 1843) was an American paleontologist, anatomist, and physician. He was the first American to devote significant time and attention to vertebrate paleontology and was one of the most importan ...
in 1825. Recent research confirms that the sloth bones were discovered in
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. Haynes Cave has been the only contender against Organ Cave as the discover ...
in
Monroe County, West Virginia Monroe County is a county in the U.S. state of West Virginia. As of the 2020 census, the population was 12,376. Its county seat is Union. Monroe County was the home of Andrew Summers Rowan of Spanish–American War fame, who is immortalized in ...
. For many decades in the twentieth century, the reported origin of Jefferson's "Certain Bones" was
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 1973, the Organ Cave System—also known as the Organ–Hedricks Cave System—was registered as a N ...
in what is now
Greenbrier County, West Virginia Greenbrier County () is a county in the U.S. state of West Virginia. As of the 2020 census, the population was 32,977. Its county seat is Lewisburg. The county was formed in 1778 from Botetourt and Montgomery counties in Virginia. History P ...
. This story was popularized in the 1920s by a local man, Andrew Price of Marlinton. The story came under scrutiny when in 1993 two fragments of a ''Megalonyx''
scapula The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eithe ...
were found in Haynes Cave in neighboring Monroe County. Smithsonian
paleontologist Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...
Frederick Grady presented evidence in 1995 confirming Haynes Cave as the original source of Jefferson's fossil. Jefferson reported that the bones had been found by
saltpeter Potassium nitrate is a chemical compound with the chemical formula . This alkali metal nitrate salt is also known as Indian saltpetre (large deposits of which were historically mined in India). It is an ionic salt of potassium ions K+ and nitrat ...
workers. He gave the cave owner's name as Frederic Crower. Correspondence between Jefferson and Colonel Stuart, who sent him the bones, indicates that the cave was located about five miles from Stuart's home and that it contained
saltpeter Potassium nitrate is a chemical compound with the chemical formula . This alkali metal nitrate salt is also known as Indian saltpetre (large deposits of which were historically mined in India). It is an ionic salt of potassium ions K+ and nitrat ...
vats. An investigation of property ownership records revealed "Frederic Crower" to be an apparent misspelling of the name Frederic Gromer. Organ Cave was never owned by Gromer, but Haynes Cave was. Two letters written by Tristram Patton, the subsequent owner of Haynes Cave, indicate that this cave was located in Monroe County near Second Creek. Monroe County had originally been part of Greenbrier County; it became a separate county shortly after the discovery of the bones. In his own letters Patton described the cave and indicated that more fossil bones remained inside. ''M. jeffersonii'' is still the most commonly identified species of ''Megalonyx''. It was designated the
state fossil Most American states have made a state fossil designation, in many cases during the 1980s. It is common to designate one species in which fossilization has occurred, rather than a single specimen, or a category of fossils not limited to a single ...
of
West Virginia West Virginia is a state in the Appalachian, Mid-Atlantic and Southeastern regions of the United States.The Census Bureau and the Association of American Geographers classify West Virginia as part of the Southern United States while the Bur ...
in 2008. ''M. leptostomus,'' named by Cope (1893), lived from the Blancan to the Irvingtonian. This species lived from Florida to Texas, north to Kansas and Nebraska, and west to New Mexico, Nevada, Oregon, and Washington. It is about half the size of ''M. jeffersonii''. It evolved into ''M. wheatleyi'', the direct ancestor of ''M. jeffersonii''. Species gradually got larger, with different species mostly based on size and geologic age.


Evolution

The first wave of Megalonychids came to North America by island-hopping across the
Central American Seaway The Central American Seaway (also known as the Panamanic Seaway, Inter-American Seaway and Proto-Caribbean Seaway) was a body of water that once separated North America from South America. It formed during the Jurassic (200–154 Ma) during the br ...
from
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...
, where ground sloths arose, prior to formation of the Panamanian land bridge. Based on molecular results, its closest living relatives are the
three-toed sloth The three-toed or three-fingered sloths are arboreal neotropical mammals . They are the only members of the genus ''Bradypus'' and the family Bradypodidae. The four living species of three-toed sloths are the brown-throated sloth, the maned sloth ...
s (''Bradypus''); earlier morphological investigations came to a different conclusion. ''M. jeffersonii'' lived from the
Illinoian Stage The Illinoian Stage is the name used by Quaternary geologists in North America to designate the period c.191,000 to c.130,000 years ago, during the middle Pleistocene, when sediments comprising the Illinoian Glacial Lobe were deposited. It precedes ...
during the
Middle Pleistocene The Chibanian, widely known by its previous designation of Middle Pleistocene, is an age in the international geologic timescale or a stage in chronostratigraphy, being a division of the Pleistocene Epoch within the ongoing Quaternary Period. The ...
(150,000 years BP) through to the
Rancholabrean The Rancholabrean North American Land Mammal Age on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from less than 240,000 years to 11,000 years BP, a p ...
of the
Late Pleistocene The Late Pleistocene is an unofficial Age (geology), age in the international geologic timescale in chronostratigraphy, also known as Upper Pleistocene from a Stratigraphy, stratigraphic perspective. It is intended to be the fourth division of ...
(11,000 BP). It belongs to the genus ''Megalonyx'', a name proposed by
Thomas Jefferson Thomas Jefferson (April 13, 1743 – July 4, 1826) was an American statesman, diplomat, lawyer, architect, philosopher, and Founding Fathers of the United States, Founding Father who served as the third president of the United States from 18 ...
, future president of the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
, in 1797. (Jefferson's surname was appended to the animal as the
specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...
in 1822 by the French zoologist
Anselme Gaëtan Desmarest Anselme Gaëtan Desmarest (6 March 1784 – 4 June 1838) was a French Zoology, zoologist and author. He was the son of Nicolas Desmarest and father of Eugène Anselme Sébastien Léon Desmarest. Desmarest was a disciple of Georges Cuvier and Alex ...
.) ''M. jeffersonii'' was probably descended from ''M. wheatleyi.''


Description

''Megalonyx'' was a large, heavily built herbivore about long. Its maximum weight is estimated at . 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 151px, Portion of a human skeleton, showing plantigrade habit In terrestrial animals, plantigrade locomotion means walking with the toes and metatarsals flat on the ground. It is one of three forms of locomotion adopted by terrestrial mammals. T ...
(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.


Paleobiology

During excavations at Tarkio Valley in southwest
Iowa Iowa () is a state in the Midwestern region of the United States, bordered by the Mississippi River to the east and the Missouri River and Big Sioux River to the west. It is bordered by six states: Wisconsin to the northeast, Illinois to the ...
, an adult ''Megalonyx'' was found in direct association with two juveniles of different ages, suggesting that adults cared for young of different generations.


Habitat

''Megalonyx'' ranged over much of North and
Central America Central America ( es, América Central or ) is a subregion of the Americas. Its boundaries are defined as bordering the United States to the north, Colombia to the south, the Caribbean Sea to the east, and the Pacific Ocean to the west. ...
. Their remains have been found as far north as
Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...
and the
Yukon Yukon (; ; formerly called Yukon Territory and also referred to as the Yukon) is the smallest and westernmost of Canada's three territories. It also is the second-least populated province or territory in Canada, with a population of 43,964 as ...
during
interglacial An interglacial period (or alternatively interglacial, interglaciation) is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age. The current Holocene in ...
intervals. ''M. jeffersonii'', also known as Jefferson's ground sloth, 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 The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico in ...
as well as along the west coast. It was the only ground sloth to range as far north as the present-day Yukon. Jefferson's ground sloth dwelled primarily in woodlands and forest, although they likely occupied a variety of habitats within these broad systems. Two recent studies were able to link directly dated specimens from the terminal Pleistocene with regional paleoenvironmental records, demonstrating that these particular animals were associated with spruce dominated, mixed conifer-hardwood habitat. In late 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 ). The
Firelands The Firelands, or Sufferers' Lands, tract was located at the western end of the Connecticut Western Reserve in what is now the U.S. state of Ohio. It was legislatively established in 1792, as the "Sufferers' Lands", and later became named "Fire Land ...
ground sloth fossil dated between 11,727 and 11,424 BCE represents the earliest-known hunting activity by
Ohio Ohio () is a state in the Midwestern region of the United States. Of the fifty U.S. states, it is the 34th-largest by area, and with a population of nearly 11.8 million, is the seventh-most populous and tenth-most densely populated. The sta ...
an Paleo-Indians.


References


Citations


Other sources

* (1871) Preliminary report on the vertebrata discovered in the
Port Kennedy Bone Cave The Port Kennedy Bone Cave is a limestone cave in the Port Kennedy section of Valley Forge National Historical Park, Pennsylvania, USA. The Bone Cave "contained one of the most important middle Pleistocene (Irvingtonian, approximately 750,000 y ...
. ''American Philosophical Society'', 12:73-102. * (1893) A preliminary report on the vertebrate paleontology of the Llano Estacado. ''4th Annual Report on the Geological Survey of Texas'': 136pp. * (1968) Plio-Pleistocene megalonychid sloths of North America. ''Bulletin of the Florida State Museum Biological Sciences'', 12(5):213-296.


External links


''Sloth Central''

Smithsonian National Zoological Park: At the Zoo - Slow and Steady Sloths
{{Taxonbar, from=Q134380 Prehistoric sloths Prehistoric placental genera Pliocene xenarthrans Pliocene mammals of North America Pleistocene xenarthrans Pleistocene mammals of North America Blancan Hemphillian Irvingtonian Rancholabrean Fossils of Canada Fossils of Guatemala Fossils of Honduras Fossils of Mexico Fossils of the United States Fossil taxa described in 1825 Taxa named by Richard Harlan Symbols of West Virginia Thomas Jefferson Ringold Formation Miocene Fauna