Macroeuphractus

''Macroeuphractus'' is a genus of extinct armadillos from the Late Miocene to Late Pliocene of South America. 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, unique among all xenarthrans.

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 Late Pliocene of Buenos Aires, Argentina. 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 , at a little over 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, central Argentina
* ''M. moreni'' is known from various Late Miocene and Pliocene sites in the Río Quinto, Ituzaingó, Epecuén and Saldungaray Formations, Argentina and the Umala 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) are fairly dedicated omnivores, but ''Macroeuphractus'' shows several features that indicate hypercarnivory:
* 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 rodents, small notoungulates and argyrolagoidean paucituberculates. Species like ''Macroeuphractus outesi'' were fairly large and presumably had an apex predator 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 Argentina. The genus occurs in an epoch where sparassodonts, phorusrhacids and sebecids 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, alongside giant opossums 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'' and phorusrhacids like '' Llallawavis''.

References

{{Taxonbar, from=Q28220739
Miocene xenarthrans
Prehistoric cingulates
Pliocene xenarthrans
Prehistoric placental genera
Neogene 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 1887