''Thylophorops'' is an extinct genus of didelphine

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 ...

from the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58South 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 ...

. Compared to their close didelphine cousins like the living '' Philander'' and ''

Didelphis ''Didelphis'' is a genus of New World marsupials. The six species in the genus ''Didelphis'', commonly known as Large American opossums, are members of the ''opossum'' order, Didelphimorphia. The genus ''Didelphis'' is composed of cat-sized om ...

'' (and like the still living ''

Lutreolina ''Lutreolina'' is a genus of opossum found in South America. Both extant species in this genus are known as lutrine opossums. They have an otter-like body plan and occasionally semiaquatic tendencies, hence the genus name ''Lutreolina'', which is ...

'') opossums, ''Thylophorops'' displays specialization towards

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 ...

, and one species, ''T. lorenzinii'', is the largest known opossum of all time, which could imply a macropredatory role.

Taxonomy

''Thylophorops'' is rather consistently recovered as a didelphine opossum, most often compared to and usually falling within the ''

'', '' Philander'' and ''

'' group. Within ''Thylophorops'' itself, there are three recognized species: * ''Thylophorops chapadmalensis'': The type species, known from the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Chapadmalalan) Chapadmalal Formation and other (up to

Uquian The Uquian age is a period of geologic time (3.0–1.5 Ma) within the Pliocene and Pleistocene epochs of the Neogene used more specifically with South American Land Mammal Ages The South American land mammal ages (SALMA) establish a geologic t ...

) formations in

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 ...

. It is known from a variety of skeletal remains, rendering it a fairly common species in the area. It is a large opossum species, comparable to the modern

Virginia opossum The Virginia opossum (''Didelphis virginiana''), also known as the North American opossum, is the only opossum living north of Mexico, its range extending south into Central America. It is the northernmost marsupial in the world. In the United S ...

in size. * ''Thylophorops lorenzinii'': Currently known only from the

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of sever ...

MLP 08-III-10-1, a lower jaw and skull fragment, coming from Late

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Buenos 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 ...

. It represents a juvenile individual, estimated to weight around , making it the largest known didelphid of all time. * ''Thylophorops perplana/perplanus'': The earliest known species, occurring in Early Pliocene Argentinian deposits.Goin, Francisco J.; Ulyses F. J. Pardinas (1996). "Revision de las especies del genero Hyperdidelphys Ameghino, 1904 (Mammalia, Marsupialia, Didelphidae. Su significacion filogenetica, estratigrafica y adaptativa en el Neogeno del Cono Sur sudamericano". Estudios Geológicos. 52 (5–6): 327–359. doi:10.3989/egeol.96525-6275.

Biology

''Thylophorops'' species (as well as several other contemporary opossum genera) show a high degree of speciation towards carnivory compared to most living didelphines. Their premolar and molar teeth were proportionally larger than those of living opossums and their grinding facets imply a more dedicated shearing action; these have been interpreted as "omnivory leading towards carnivory" and as more specialized carnivory in posterior studies. There is evidence that ''T. chapadmalensis'' re-appropriated burrows from other digging mammals, as well as outright consuming them. ''Thylophorops'' species as a whole tended to be terrestrial rather than arboreal.

Paleoecology

''Thylophorops'' lived at a time when South America's older predatory guilds were dismantling. It co-existed with only a few

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 ...

and

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 ...

taxa like ''

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 '' Llallawavis'', and it, as well as similar opossum species, evolved to fill the ecological blanks. A similar case is observed with the carnivorous armadillo '' Macroeuphractus'', a product of this same era of faunal turn-overs. As mentioned above, there is evidence of ''T. chapadmalensis'' predating on contemporary

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 ...

s and appropriating burrows, from them or other mammals such as armadillos.

References

{{Taxonbar, from=Q3805941 †Thylophorops Pliocene mammals of South America Prehistoric marsupial genera Chapadmalalan Huayquerian Uquian Neogene Argentina Fossils of Argentina Fossil taxa described in 1908 Taxa named by Florentino Ameghino