''Macroeuphractus'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of extinct armadillos from the Late Miocene to

Late Pliocene Late may refer to: * LATE, an acronym which could stand for: ** Limbic-predominant age-related TDP-43 encephalopathy, a proposed form of dementia ** Local-authority trading enterprise, a New Zealand business law ** Local average treatment effect, ...

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 sout ...

. The genus is noted for its large size, with ''Macroeuphractus outesi'' being the largest non- pampathere or glyptodont armadillo discovered, as well as its specializations for

carnivory A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other so ...

, unique among all

xenarthra Xenarthra (; from Ancient Greek ξένος, xénos, "foreign, alien" + ἄρθρον, árthron, "joint") is a major clade of placental mammals native to the Americas. There are 31 living species: the anteaters, tree sloths, and armadillos. ...

ns.

Description

There are three currently recognised species of ''Macroeuphractus'': ''M. outesi'', ''M. retusus'' and ''M. moreni''. The former, the type species, is known from one specimen from the

Buenos Aires Buenos Aires ( or ; ), officially the Autonomous City of Buenos Aires ( es, link=no, Ciudad Autónoma de Buenos Aires), is the capital and primate city of Argentina. The city is located on the western shore of the Río de la Plata, on South ...

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

. This specimen is composed of a fairly well preserved skull as well as numerous post-cranial elements. It represented a considerably large species at around , although it is possible that it was actually closer to 30 kg, at a little over a meter in length it would still be a decently sized predator.

Species

* ''M. retusus'' is known from a single lower jaw from the

Cerro Azul Formation The Cerro Azul Formation ( es, Formación Cerro Azul), in the Buenos Aires Province also described as Epecuén Formation, is a geological formation of Late Miocene (Tortonian, or Huayquerian in the SALMA classification) age in the Colorado Basin ...

, central

* ''M. moreni'' is known from various Late Miocene and Pliocene sites in the Río Quinto, Ituzaingó, Epecuén and Saldungaray Formations,

and the

Umala Umala is a location in La Paz in Bolivia. It is the seat of the Umala Municipality, the second municipal section of the Aroma Province Aroma is one of the twenty provinces of the Bolivian La Paz Department. It is situated in the southern part ...

and La Paz Formations, Bolivia''Macroeuphractus''
at Fossilworks.org

Classification

''Macroeuphractus'' is traditionally grouped with euphractines; it was named after its similarity with '' Euphractus'' itself. The most recent phylogenetic examinations confirm its status as at least a sister group to euphractines, along with '' Paleuphractus'', '' Doellotatus'' and '' Proeuphractus''.

Biology

''Macroeuphractus'' is one of the few known xenarthrans to have specialised extensively for a carnivorous lifestyle. Modern euphractine armadillos (such as the modern

six-banded armadillo The six-banded armadillo (''Euphractus sexcinctus''), also known as the yellow armadillo, is an armadillo found in South America. The sole extant member of its genus, it was first described by Swedish zoologist Carl Linnaeus in 1758. The six-b ...

) are fairly dedicated omnivores, but ''Macroeuphractus'' shows several features that indicate

hypercarnivory A hypercarnivore is an animal which has a diet that is more than 70% meat, either via active predation or by scavenging. The remaining non-meat diet may consist of non-animal foods such as fungi, fruits or other plant material. Some extant examp ...

: * large, conical caniniform teeth * an enlarged temporal fossa * more developed muscles pertaining to the temporalis musculature (as evidenced by the more prominent muscle scars) * a deeper rostrum * more powerful anterior teeth (particularly in the enlarged and caniniform M2) * a deeper and more robust zygomatic arch * a greater moment arm of the temporalis muscle than in other armadillos These features are unusual among xenarthrans but are more in line with predatory mammal groups. Like most armadillos, ''Macroeuphractus'' was fossorial, and it probably could dig out small and medium-sized mammals such as

caviomorph Caviomorpha is the rodent infraorder or parvorder that unites all New World hystricognaths. It is supported by both fossil and molecular evidence. The Caviomorpha was for a time considered to be a separate order outside the Rodentia, but is now ...

rodents, small

notoungulate Notoungulata is an extinct order of mammalian ungulates that inhabited South America from the early Paleocene to the Holocene, living from approximately 61 million to 11,000 years ago. Notoungulates were morphologically diverse, with forms resemb ...

s and argyrolagoidean paucituberculates. Species like ''Macroeuphractus outesi'' were fairly large and presumably had an

apex predator An apex predator, also known as a top predator, is a predator at the top of a food chain, without natural predators of its own. Apex predators are usually defined in terms of trophic dynamics, meaning that they occupy the highest trophic lev ...

status in their faunal communities.

Paleoecology

''Macroeuphractus moreni'' was a rather widespread species, and played a role in various faunal communities in the Miocene and Pliocene epochs of South America, while the other two species had a more limited range in

. The genus occurs in an epoch where

sparassodont Sparassodonta (from Greek to tear, rend; and , gen. , ' tooth) is an extinct order of carnivorous metatherian mammals native to South America, related to modern marsupials. They were once considered to be true marsupials, but are now though ...

phorusrhacid Phorusrhacids, colloquially known as terror birds, are an extinct clade of large carnivorous flightless birds that were one of the largest species of apex predators in South America during the Cenozoic era; their conventionally accepted temporal ...

s and

sebecid Sebecidae is an extinct family of prehistoric terrestrial sebecosuchian crocodylomorphs. The oldest known member of the group is ''Ogresuchus furatus'' known from the Upper Cretaceous (Maastrichtian) Tremp Formation (Spain). Sebecids were di ...

s entered in decline, and was among the various mammal groups to exploit this ecological vacancy prior to the arrival of North American carnivorans in the

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in ...

, alongside giant

opossums Opossums () are members of the marsupial order Didelphimorphia () endemic to the Americas. The largest order of marsupials in the Western Hemisphere, it comprises 93 species in 18 genera. Opossums originated in South America and entered North A ...

such as '' Thylophorops''.Prevosti, Francisco J.; Analía Forasiepi; Natalia Zimicz (2013). "The Evolution of the Cenozoic Terrestrial Mammalian Predator Guild in South America: Competition or Replacement?". Journal of Mammalian Evolution. 20: 3–21. doi:10.1007/s10914-011-9175-9. Nonetheless, ''Macroeuphractus'' still co-existed with late surviving sparassodonts such as ''

Thylacosmilus ''Thylacosmilus'' is an extinct genus of saber-toothed metatherian mammals that inhabited South America from the Late Miocene to Pliocene epochs. Though ''Thylacosmilus'' looks similar to the " saber-toothed cats", it was not a felid, like the ...

'' and phorusrhacids like '' Llallawavis''.

References

{{Taxonbar, from=Q28220739 Prehistoric cingulates Pliocene xenarthrans Prehistoric placental genera Miocene mammals of South America Pliocene mammals of South America Chapadmalalan Montehermosan Huayquerian Neogene Argentina Fossils of Argentina Cerro Azul Formation Ituzaingó Formation Neogene Bolivia Fossils of Bolivia Fossil taxa described in 1889