''Machlydotherium'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually 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 ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

cingulate Cingulata, part of the superorder Xenarthra, is an order of armored New World placental mammals. Dasypodids and chlamyphorids, the armadillos, are the only surviving families in the order. Two groups of cingulates much larger than extant arm ...

of uncertain systematic affinities, perhaps belonging to the

Pampatheriidae Pampatheriidae ("Pampas beasts") is an extinct family of large plantigrade armored armadillos related to extant armadillos in the order Cingulata. However, pampatheriids have existed as a separate lineage since at least the middle Eocene Muster ...

. It lived from the Middle

Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

to the Early

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

, and its fossilized remains were found in

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

Description

This animal is only known from isolated

osteoderm Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinct amp ...

s, who were large and thick, quite similar to those of the later

pampathere Pampatheriidae ("Pampas beasts") is an extinct family of large plantigrade armored armadillos related to extant armadillos in the order Cingulata. However, pampatheriids have existed as a separate lineage since at least the middle Eocene Mus ...

s. Some of these osteoderms, belonging to the fixed carapace typical of many cingulates, show the start of the differentiation of secondary figures, and large central follicles. The mobile osteoderms were distinguished from those of pampatheres by a little differentiated and rough surface. A bilobed tooth, similar to those of pampatheres, but whose abrasion surface draw a cusp in the anterior section, has also been attributed to the genus ''Machlydotherium''.

Classification

The genus ''Machlydotherium'' was first described in 1902 by

Florentino Ameghino Florentino Ameghino (born Giovanni Battista Fiorino Giuseppe Ameghino September 19, 1853 – August 6, 1911) was an Argentine naturalist, paleontologist, anthropologist and zoologist, whose fossil discoveries on the Argentine Pampas, especially ...

, the name itself being an anagram of '' Chlamydotherium'', another genus of cingulates. The type species, ''Machlydotherium asperum'', dates from the Late

, but osteoderms attributed to the genus have also been found in terrains dated from the Middle Eocene to the Early

. Ameghino described several species besides the type species, such as ''Machlydotherium ater'', ''M. sparsum'' and ''M. intortum'', the latter now erected as its own genus, '' Yuruatherium''. Due to the scarcity of its remains, its antiquity and the specificities of the shape of its osteoderms, ''Machlydotherium'' can hardly be placed in a specific clade of cingulate. It seems to have been close to the

s, the oldest of which only dating back from the Middle

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

. It is possible that ''Machlydotherium'' evolved independently from the pampatheres, becoming extinct without leaving known descendants during the Oligocene.

Bibliography

*F. Ameghino. 1902. Notices préliminaires sur des mammifères nouveaux des terrains Crétacé de Patagonie {preliminary notes on new mammals from the Cretaceous terrains of Patagonia]. Boletin de la Academia Nacional de Ciencias de Córdoba 17:5-70 *G. G. Simpson. 1948. The beginning of the age of mammals in South America. Part I. Bulletin of the American Museum of Natural History 91:1-232 *M. C. McKenna and S. K. Bell. 1997. Classification of Mammals Above the Species Level 1–640 * Ciancio M. R. Carlini A. A. Campbell K. E. Scillato-Yané G. J. . 2013. New Palaeogene cingulates (Mammalia, Xenarthra) from Santa Rosa, Perú and their importance in the context of South American faunas. Journal of Systematic Palaeontology 11:727–741. {{Taxonbar, from=Q60978086 Prehistoric cingulates Prehistoric placental genera Eocene xenarthrans Eocene genus first appearances Eocene mammals of South America Oligocene mammals of South America Oligocene xenarthrans Oligocene genus extinctions Paleogene Argentina Fossils of Argentina Fossils of Brazil Paleogene Brazil Tinguirirican Divisaderan Mustersan Fossil taxa described in 1927 Taxa named by Florentino Ameghino Golfo San Jorge Basin Sarmiento Formation