''Megistonyx'' is an extinct genus 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 Cari ...

endemic to South America during the

Late Pleistocene The Late Pleistocene is an unofficial age in the international geologic timescale in chronostratigraphy, also known as Upper Pleistocene from a stratigraphic perspective. It is intended to be the fourth division of the Pleistocene Epoch within ...

(

Lujanian The Lujanian age is a South American land mammal age within the Pleistocene and Holocene epochs of the Neogene, from 0.8–0.011 Ma or 800–11 tya. It follows the Ensenadan. The age is usually divided into the middle Pleistocene Bonaerian stage ...

). It is known from one skeleton collected in the Andes of

Venezuela Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many islands and islets in ...

, and is closely related to '' Ahytherium''.

History of discovery

The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of seve ...

(and so far only known) specimen was found in a cave called ''Cueva de los Huesos'' (meaning "Bone Cave") on

Cerro Pintado Cerro Pintado is a mountain in South America. It has an elevation above sea level and sits on the international border between Colombia and Venezuela. See also * List of Ultras of South America This is a list of the 209 Ultra-prominent peak, u ...

, a mountain found in the

Serranía del Perijá The Serranía del Perijá, Cordillera de Perijá or Sierra de Perijá is a mountain range, an extension of the eastern Andean branch ( Cordillera Oriental), in northern South America, between Colombia and Venezuela, ending further north in the ...

range of the

Andes The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...

, in the extreme northernmost part of the

Sierra de Perijá National Park Sierra de Perijá National Park, also known as Perijá National Park, is a protected area in Venezuela. It is located in the Serranía de Perijá mountains on the border with Colombia, to the southwest of Zulia state and Lake Maracaibo. The park w ...

on the border between Venezuela and Colombia at an altitude of . The various known pieces of the skeleton were recovered in two expeditions to the cave in 1993 and 1997. The specimen was found in a scattered condition, with some bones being damaged, notably the skull was missing the left

Squamosal bone The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone. In most tetrapods, the squamosal and quadratojugal bones form the cheek series of the skull. The bone forms an ancestral co ...

. The specimen is currently known from the aforementioned skull, both a right and left

humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...

, a left

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 ...

, two

thoracic vertebrae In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebrae and they are intermediate in size between the cervical ...

, a complete

rib In vertebrate anatomy, ribs ( la, costae) are the long curved bones which form the rib cage, part of the axial skeleton. In most tetrapods, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the ch ...

and three rib fragments. There is apparently more of the specimen left in-situ in the cave. The age of the specimen was found to be approximately 17,300

Cal BP Before Present (BP) years, or "years before present", is a time scale used mainly in archaeology, geology and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Bec ...

Distribution and habitat

The specimen is approximately 17,000 years old, this would put the specimen just after the retreat of the glaciers after the

Last Glacial Maximum The Last Glacial Maximum (LGM), also referred to as the Late Glacial Maximum, was the most recent time during the Last Glacial Period that ice sheets were at their greatest extent. Ice sheets covered much of Northern North America, Northern Eu ...

, which could indicate a cold climate. However, the specimen is associated with fossils of ''

Neochoerus ''Neochoerus'' ("new hog") is an extinct genus of rodent closely related to the living capybara The capybaraAlso called capivara (in Brazil), capiguara (in Bolivia), chigüire, chigüiro, or fercho (in Colombia and Venezuela), carpincho ( ...

'' (an extinct

capybara The capybaraAlso called capivara (in Brazil), capiguara (in Bolivia), chigüire, chigüiro, or fercho (in Colombia and Venezuela), carpincho (in Argentina, Paraguay and Uruguay) and ronsoco (in Peru). or greater capybara (''Hydrochoerus hydro ...

) '' Mazama'' (brocket deer) and ''

Tayassu The white-lipped peccary (''Tayassu pecari'') is a species of peccary found in Central and South America and the only member of the genus ''Tayassu''. Multiple subspecies have been identified. White-lipped peccaries are similar in appearance t ...

'' (peccary), which could indicate a warmer, perhaps savanna-like climate.

References

{{Taxonbar, from=Q30693620 Prehistoric sloths Prehistoric placental genera Pleistocene xenarthrans Holocene extinctions Pleistocene mammals of South America Lujanian Pleistocene Venezuela Fossils of Venezuela Fossil taxa described in 2013