Megatheriidae
Encyclopedia
Megatheriidae is a family of extinct
ground sloth
s that lived from approximately 23 mya—11,000 years ago, existing for approximately .
Megatheriids appeared later in the Oligocene, some 30 million years ago, also in South America. The group includes the heavily-built Megatherium
(given its name 'great beast' by Georges Cuvier
) and Eremotherium
. Other megatheriids, such as the more slightly built nothrotheres Hapalops
and Nothrotheriops
, reached a length of about 1.2 meters. The nothrotheres have recently been placed in their own family, Nothrotheriidae.
The skeletal structure of these ground sloths indicates that the animals were massive. Their thick bones and even thicker joints (especially those on the hind legs) gave their appendages tremendous power that, combined with their size and fearsome claws, provided a formidable defense against predators.
The earliest megatheriid in North America was Eremotherium eomigrans which arrived 2.2 million years ago, after crossing the recently formed Panama
nian land bridge. With more than five tons in weight, 6 meters in length, and able to reach as high as 17 feet (5.2 m), it was taller than an African Bush Elephant
bull. Unlike relatives, this species retained a plesiomorphic extra claw. While other species of Eremotherium had four fingers with only two or three claws, E. eomigrans had five fingers, four of them with claws up to nearly a foot long.
The last ground sloths in North America belonging to Nothrotheriops died so recently that their petrified dung (coprolite
s) has remained undisturbed in some caves, as if it were just recently deposited. One of the skeletons, found in a lava tube
(cave) at Aden Crater, adjacent to Kilbourne Hole
, New Mexico
, still had skin and hair preserved, and is now at the Yale Peabody Museum. The American Museum of Natural History
in New York City has a sample of dung with a note attached to it that reads "deposited by Theodore Roosevelt
". The largest samples of Nothrotheriops dung can be found in the collections of the Smithsonian Museum.
FAMILY †MEGATHERIIDAE Gray, 1821
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...
ground sloth
Ground sloth
Ground sloths are a diverse group of extinct sloths, in the mammalian superorder Xenarthra. Their most recent survivors lived in the Antilles, where it has been proposed they may have survived until 1550 CE; however, the youngest AMS radiocarbon date reported is 4190 BP, calibrated to c. 4700 BP...
s that lived from approximately 23 mya—11,000 years ago, existing for approximately .
Megatheriids appeared later in the Oligocene, some 30 million years ago, also in South America. The group includes the heavily-built Megatherium
Megatherium
Megatherium was a genus of elephant-sized ground sloths endemic to Central America and South America that lived from the Pliocene through Pleistocene existing approximately...
(given its name 'great beast' by Georges Cuvier
Georges Cuvier
Georges Chrétien Léopold Dagobert Cuvier or Jean Léopold Nicolas Frédéric Cuvier , known as Georges Cuvier, was a French naturalist and zoologist...
) and Eremotherium
Eremotherium
Eremotherium is an extinct genus of actively mobile ground sloth of the family Megatheriidae, endemic to North America and South America during the Pleistocene epoch...
. Other megatheriids, such as the more slightly built nothrotheres Hapalops
Hapalops
Hapalops is an extinct genus of ground sloth from the late Oligocene of South America.Though related to the giant Megatherium, Hapalops was much smaller, measuring about in length. Like most extinct sloths it is categorized as a ground sloth, but it is believed that the smaller size of Hapalops...
and Nothrotheriops
Nothrotheriops
Nothrotheriops is a genus of Pleistocene ground sloth found in North and South America. This genus of bear-sized xenarthran was related to the much larger, and far more famous Megatherium, although it has recently been placed in a different family, Nothrotheriidae.-Discovery and species:Fossils of...
, reached a length of about 1.2 meters. The nothrotheres have recently been placed in their own family, Nothrotheriidae.
The skeletal structure of these ground sloths indicates that the animals were massive. Their thick bones and even thicker joints (especially those on the hind legs) gave their appendages tremendous power that, combined with their size and fearsome claws, provided a formidable defense against predators.
The earliest megatheriid in North America was Eremotherium eomigrans which arrived 2.2 million years ago, after crossing the recently formed Panama
Panama
Panama , officially the Republic of Panama , is the southernmost country of Central America. Situated on the isthmus connecting North and South America, it is bordered by Costa Rica to the northwest, Colombia to the southeast, the Caribbean Sea to the north and the Pacific Ocean to the south. The...
nian land bridge. With more than five tons in weight, 6 meters in length, and able to reach as high as 17 feet (5.2 m), it was taller than an African Bush Elephant
African Bush Elephant
The African Bush Elephant or African Savanna Elephant is the larger of the two species of African elephant. Both it and the African Forest Elephant have usually been classified as a single species, known simply as the African Elephant...
bull. Unlike relatives, this species retained a plesiomorphic extra claw. While other species of Eremotherium had four fingers with only two or three claws, E. eomigrans had five fingers, four of them with claws up to nearly a foot long.
The last ground sloths in North America belonging to Nothrotheriops died so recently that their petrified dung (coprolite
Coprolite
A coprolite is fossilized animal dung. Coprolites are classified as trace fossils as opposed to body fossils, as they give evidence for the animal's behaviour rather than morphology. The name is derived from the Greek words κοπρος / kopros meaning 'dung' and λιθος / lithos meaning 'stone'. They...
s) has remained undisturbed in some caves, as if it were just recently deposited. One of the skeletons, found in a lava tube
Lava tube
Lava tubes are natural conduits through which lava travels beneath the surface of a lava flow, expelled by a volcano during an eruption. They can be actively draining lava from a source, or can be extinct, meaning the lava flow has ceased and the rock has cooled and left a long, cave-like...
(cave) at Aden Crater, adjacent to Kilbourne Hole
Kilbourne Hole
Kilbourne Hole is a maar volcanic crater, located west of the Franklin mountains of El Paso, Texas, in the Potrillo Volcanic Field of Doña Ana County, New Mexico. Nearby Hunt's Hole lies several miles just south of Kilbourne Hole. These holes are rare examples of volcanic action without a...
, New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
, still had skin and hair preserved, and is now at the Yale Peabody Museum. The American Museum of Natural History
American Museum of Natural History
The American Museum of Natural History , located on the Upper West Side of Manhattan in New York City, United States, is one of the largest and most celebrated museums in the world...
in New York City has a sample of dung with a note attached to it that reads "deposited by Theodore Roosevelt
Theodore Roosevelt
Theodore "Teddy" Roosevelt was the 26th President of the United States . He is noted for his exuberant personality, range of interests and achievements, and his leadership of the Progressive Movement, as well as his "cowboy" persona and robust masculinity...
". The largest samples of Nothrotheriops dung can be found in the collections of the Smithsonian Museum.
FAMILY †MEGATHERIIDAE Gray, 1821