Megalonyx (
GreekGreek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical...
, "great claw") is an extinct
genusIn biology, a genus is a taxonomic unit used in the classification of living and fossil organisms. The term comes from Latin genus "descent, family, type, gender" , cognate with – genos, "race, stock, kin" ..In addition, genus is a taxonomic rank in the hierarchy In biology, a genus (plural:...
of giant ground sloths living from the
HemphillianThe Hemphillian 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 10,300,000 to 4,900,000 years BP, a period of . It is usually considered to overlap the Tortonian epoch of the Late...
of the
Late MioceneThe Late Miocene is a sub-epoch of the Miocene Epoch made up of two stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch....
(6 million years
BPBefore 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 1 January 1950 as the arbitrary origin of the age scale...
) through to the
RancholabreanThe 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 300,000 to 11,000 years BP, a period of . It is usually considered to overlap the Middle Pleistocene and Late...
of the
Late PleistoceneThe Late Pleistocene is a stage of the Pleistocene Epoch. The beginning of the stage is defined by the base of Eemian interglacial phase before final glacial episode of 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). Their closest living relatives are the
two-toed slothCholoepus is a genus of mammals 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...
s (
Choloepus).
Endemic to
North AmericaNorth America is the northern continent of the Americas, situated in the Earth's northern hemisphere and in the western hemisphere. It is bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the southeast by the Caribbean Sea, and on the west by the North Pacific...
, these animals are the most widespread fossils of the family
MegalonychidaeMegalonychidae is a group of sloths including the extinct Megalonyx and the living two toed sloths. Megalonychids first appeared in the early Oligocene, about 35 million years ago, in southern Argentina , and spread as far as the Antilles by the early Miocene...
. They evolved from
Pliometanastes with the earlier ancestral species being
Megalonyx wheatleyi. Their remains have been found as far north as
AlaskaAlaska is the largest state of the United States of America 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...
and the
YukonYukon , or The Yukon, is the westernmost and smallest of Canada's three federal territories. It was named after the Yukon River, Yukon meaning "Great River" in Gwich’in....
.
The generic name
Megalonyx was proposed by future U.S.
Megalonyx (
GreekGreek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical...
, "great claw") is an extinct
genusIn biology, a genus is a taxonomic unit used in the classification of living and fossil organisms. The term comes from Latin genus "descent, family, type, gender" , cognate with – genos, "race, stock, kin" ..In addition, genus is a taxonomic rank in the hierarchy In biology, a genus (plural:...
of giant ground sloths living from the
HemphillianThe Hemphillian 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 10,300,000 to 4,900,000 years BP, a period of . It is usually considered to overlap the Tortonian epoch of the Late...
of the
Late MioceneThe Late Miocene is a sub-epoch of the Miocene Epoch made up of two stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch....
(6 million years
BPBefore 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 1 January 1950 as the arbitrary origin of the age scale...
) through to the
RancholabreanThe 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 300,000 to 11,000 years BP, a period of . It is usually considered to overlap the Middle Pleistocene and Late...
of the
Late PleistoceneThe Late Pleistocene is a stage of the Pleistocene Epoch. The beginning of the stage is defined by the base of Eemian interglacial phase before final glacial episode of 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). Their closest living relatives are the
two-toed slothCholoepus is a genus of mammals 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...
s (
Choloepus).
Endemic to
North AmericaNorth America is the northern continent of the Americas, situated in the Earth's northern hemisphere and in the western hemisphere. It is bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the southeast by the Caribbean Sea, and on the west by the North Pacific...
, these animals are the most widespread fossils of the family
MegalonychidaeMegalonychidae is a group of sloths including the extinct Megalonyx and the living two toed sloths. Megalonychids first appeared in the early Oligocene, about 35 million years ago, in southern Argentina , and spread as far as the Antilles by the early Miocene...
. They evolved from
Pliometanastes with the earlier ancestral species being
Megalonyx wheatleyi. Their remains have been found as far north as
AlaskaAlaska is the largest state of the United States of America 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...
and the
YukonYukon , or The Yukon, is the westernmost and smallest of Canada's three federal territories. It was named after the Yukon River, Yukon meaning "Great River" in Gwich’in....
.
Fossils
The generic name
Megalonyx was proposed by future U.S. President
Thomas JeffersonThomas Jefferson was the third President of the United States , the principal author of the Declaration of Independence , and one of the most influential Founding Fathers for his promotion of the ideals of republicanism in the United States...
in 1797, based on fossil specimens of what later came to be called
Megalonyx jeffersoniiMegalonyx jeffersonii, or Jefferson's ground sloth, is an extinct species of giant ground sloth that lived from the Illinoian glaciation during the Middle Pleistocene through to the Rancholabrean of the Late Pleistocene . It was the last surviving member of the family Megalonychidae.This species...
that he had received from western
VirginiaThe Commonwealth of Virginia is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" because it is the birthplace of eight U.S. presidents. The geography and climate of the state are shaped by the Blue...
. His presentation to the
American Philosophical SocietyThe American Philosophical Society is a discussion group founded in 1743 by Benjamin Franklin as an offshoot of his earlier club, the Junto...
that year is often credited as the beginning of
vertebrate paleontologyVertebrate paleontology seeks to discover the behavior, reproduction and appearance of extinct animals with vertebrae or a notochord, through the study of their fossilized remains...
in
North AmericaNorth America is the northern continent of the Americas, situated in the Earth's northern hemisphere and in the western hemisphere. It is bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the southeast by the Caribbean Sea, and on the west by the North Pacific...
.
Ongoing excavations at Tarkio Valley in southwest
IowaIowa is a state located in the Midwestern region of the United States of America, an area often referred to as the "American Heartland." It derives its name from the Ioway people, one of the many American Indian tribes that occupied the state at the time of European exploration. Iowa was a part of...
may reveal something of the familial life of
Megalonyx. An adult was found in direct association with two juveniles of different ages, suggesting that adults cared for young of different generations.
Range
Megalonyx's range encompassed most of
North AmericaNorth America is the northern continent of the Americas, situated in the Earth's northern hemisphere and in the western hemisphere. It is bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the southeast by the Caribbean Sea, and on the west by the North Pacific...
from central
AlaskaAlaska is the largest state of the United States of America 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...
to central
FloridaFlorida is a state located in the southeastern region of the United States, bordering Alabama to the northwest and Georgia to the north. It was the 27th state admitted to the United States...
with
palynologyPalynology is the science that studies contemporary and fossil palynomorphs, including pollen, spores, orbicules, dinoflagellate cysts, acritarchs, chitinozoans and scolecodonts, together with particulate organic matter and kerogen found in sedimentary rocks and sediments...
records indicating this animal resided in a moist and cool climate. Records also indicate this was a
spruce-dominatedA spruce is a tree of the genus Picea , a genus of about 35 species of coniferous evergreen trees in the Family Pinaceae, found in the northern temperate and boreal regions of the earth. Spruces are large trees, from 20–60 m tall when mature, and can be distinguished by their whorled branches and...
environment. It should be noted that
M. jeffersoni was larger in size in the southern part of its range and smaller in the northern part.
Other sources
(1871) Preliminary report on the vertebrata discovered in the Port Kennedy Bone Cave.
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