Mylodon was named by Richard Owen on the basis of a nearly complete lower jaw with teeth, which was found by Charles Darwin in a consolidated gravel cliff at Bahía Blanca, during the survey expedition of HMS Beagle.

The discovery of fresh-looking samples of skin and dung sparked a small wave of expeditions during the early 20th century to search for a living example of the animal.

Well preserved samples of Mylodon remains have been discovered in the Cueva del Milodón site in Patagonia, Chile along the southern flank of Cerro Benítez in the year 1896.

[4] The American Museum of Natural History has exhibited a sample of Mylodon dung from Argentina with a note that reads "deposited by Theodore Roosevelt".

The flat, flap-like and largely indented structure of the molariform teeth can be emphasized as a characteristic of the mylodonts, which clearly differs from that of the Megatheriidae and Megalonychidae with their two transverse raised ridges per tooth.

The typically more complex bilobed design of the molar-like teeth of Glossotherium and Lestodon, caused by a central constriction, only occurred on the lower rearmost tooth in Mylodon.

The most important location for such finds is the Cueva del Milodón in the Chilean province of Última Esperanza, where the first skin parts were brought to light at the end of the 19th century.

[31][32][33] In the Pampa region, the northern limit was found approximately at the Chuí River in the southeastern Brazilian state of Rio Grande do Sul around 30 degrees south latitude.

[39] Among the early and more northerly finds of Mylodon is, for example, a skull from the El Palmar Formation in the Argentine province of Entre Ríos, which dates to the end of the last warm period about 80,000 years ago.

These include the important archaeological site of Paso Otero in Buenos Aires Province, the locality of Arroyo de Vizcaíno in southern Uruguay, and the Chuí River.

From here come, among other things, skeletal remains of two individuals of Mylodon, distributed in each case over a narrowly defined area, but in two different stratigraphic units and at a spatial distance of 21 m from each other.

Other finds belong to camels such as Lama, horses such as Hippidion or South American ungulates such as Macrauchenia, in addition, several predators are represented, including the jaguar, Smilodon as a member of the saber-toothed cats, and the giant bear form Arctotherium.

[51] Urumacotherium Pseudoprepotherium Paroctodontotherium Octodontotherium Brievabradys Lestodon Bolivartherium Thinobadistes Sphenotherus Lestobradys Pleurolestodon Glossotheridium Simomylodon Kiyumylodon Mylodon Paramylodon Glossotherium Recent molecular sequence results obtained using collagen[52] and mitochondrial DNA[53] extracted from fossils indicate that the closest living relatives of Mylodon are the two-toed sloths of genus Choloepus.

Owen, one of the most important explorers of the Victorian era, was concerned from 1836 with fossil finds brought back by Charles Darwin from his pioneering voyage on HMS Beagle to South America.

The collection also included a mandible from Punta Alta near Bahía Blanca in the south of the Argentina Buenos Aires Province (specimen number NHM 16617).

This form was based on a mandible and clavicle, both of which came from the Big Bone Lick in Boone County in the U.S. state of Kentucky, and which Richard Harlan had already described in 1831 under the species assignment Megalonyx laqueatus.

In contrast to Mylodon, for which Owen assumed a kinship proximity to the other large ground sloths known at the time, such as Megatherium or Megalonyx, he placed Glossotherium in a series with the anteaters and with the pangolins, respectively, and postulated an insectivorous lifestyle for the animals.

This occurred in the course of processing a nearly complete skeleton that had been discovered the year before in the flood plains of the Río de la Plata north of Buenos Aires.

The largely intact skull was characterized by a short and broad snout and by a dentition consisting of a total of 18 teeth, of which the foremost tooth in each case showed a canine design.

Based on the similarities in dental structure with the flat, molar-like teeth, Owen placed the skeleton in the genus Mylodon and introduced the new species M. robustus.

[57][60] A skull including mandible found at Pergamino in Buenos Aires Province served the Danish zoologist Johannes Theodor Reinhardt (1816-1882) in 1879 as the basis for a comprehensive description.

Reinhardt noticed similarities to M. darwinii in the construction of the lower jaw, but in the skull design his find deviated clearly from the broad-nosed M. robustus by the narrow snout.

The ungulates are mostly used as analogous examples, in which shapes with high tooth crowns and broad-lipped mouths are usually grass-eating, such as various cattle, horses or the white rhinoceros.

In contrast, those with low tooth crowns and narrow snouts such as the duiker or the black rhinoceros feed largely selective from various leaves and other soft vegetable foods.

A special feature is the closed nasal arch, which is heavily roughened in its front area and thus offers muscle attachment points for a mobile upper lip.

In contrast to the sometimes huge representatives of the Megatheriidae, the joint between the lower jaw and the skull of the Mylodonts was relatively low, roughly at the chewing level of the teeth.

The resulting decreasing lever arm of the masseter muscle experiences through the structure of the zygomatic arch, mainly of the descending process, a certain compensation, so that there should have been only minor differences to the Megatheria with regard to the biting force.

Such a digestive system could reduce the amount of processed food in the mouth and thus ultimately also have compensated for the small total chewing surface in Mylodon.

A functionally similar but fundamentally different hand position can be found in the ankle duct of the distantly related present-day great anteater.

The rare signs of wear and tear on the last phalanx, which are isolated from the Cueva del Milodón several times, can serve as an additional indicator of digging activities.