Description
''Diabolotherium'' is a relatively small member of the Megatherioidea, though its specific phylogenetic position is unclear. It is known from a number of individual bones and a partial skeleton. A complete skull is known, but has not yet been described.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 datin ...Etymology
The generic name commemorates the type location, Casa del Diablo Cave. The specific epithet ''nordenskioldi'' refers to Erland Nordenskioldi as the discoverer of the holotype, and was already in use by Lucas Kraglievich in 1926 when the specific epithet "Nothropus" ''nordenskioldi'' was assigned.Taxonomy
The taxon was originally described in 1926 by Kraglievich as a member of the genus '' Nothropus'', when it was redescribed in 2007, it was found to be distinct enough to be placed in the separate genus ''Diabolotherium'' and was placed in the familyPaleobiology
''Diabolotherium'' is noteworthy for its the long and slender limb bones, which are rarely found in other extinct sloths and usually appear shorter and more robust. However, they are similar to those of today's tree sloths. The clearly spherical head of the humerus is characteristic of all sloths, which enables a very flexible arm movement in connection with the shoulder blade. Above all, the design of the upper articular process of the ulna, the olecranon, is decisive for the main activity of secondary articular animals and other mammals. The olecranon is extremely long in burrowing secondary articulated animals, such as armadillos or some large ground sloths. This enables the animals to muster the strength they need to dig, as the triceps that attach here increases the leverage due to the greater length of the appendage. Purely terrestrial forms have a much shorter extension, but the shortest occurs in today's sloths hanging with their backs down in the branches. ''Diabolotherium'' has a longer olecranon than the recent sloths, but it is significantly shorter than that of burrowing representatives. Its proportions correspond roughly to those of the extinct ''Hapalops'', to which semi- scansorial locomotion is attributed, whereby the climbing method corresponded more to that of today's tamanduas. The fact that ''Diabolotherium'' was able to climb is supported by the upper joint capsule of the ulna, which circumscribes an open circle of about 105 ° and is therefore extraordinarily wide. Together with the lower joint of the humerus that engages here, it forms the elbow joint, The wide opening of the joint capsule of the ulna gave the forearm significantly more freedom of movement. In connection with the position of the spoke pushed in front of the ulna and its circular, upper head, it can be assumed that the forearm could be turned in and out very well and was overall very mobile. This resulted in a highly flexible upper-lower arm connection. Several bone ridges on the shaft of the spoke also show strongly developed forearm muscles, which in turn led to a more rotatable hand, which is also confirmed by the sometimes short design of some carpal bones. The three equally long rays of the hand in turn indicate an increased ability to grip, which was severely limited in the large ground sloths. ''Diabolotherium'' is one of the few extinct sloths known to have pursued this type of locomotion. The climbing locomotion of ''Diabolotherium'' was originally associated with a solely arboreal way of life, analogous to today's sloths or some forms known from the Lower Miocene of theReferences
{{Taxonbar, from=Q19278158 Prehistoric sloths Pleistocene xenarthrans Prehistoric placental genera Pleistocene mammals of South America Lujanian Pleistocene Peru Fossils of Peru Pleistocene Chile Fossils of Chile Holocene extinctions Fossil taxa described in 2007