''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 Nort ...
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. 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 ...
'' (and like the still living '' Lutreolina'') opossums, ''Thylophorops'' displays specialization towards carnivory, 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 ''
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 ...
'', '' Philander'' and '' Lutreolina'' 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
The Chapadmalalan age is a period of geologic time (4.0–3.0 Ma) within the Pliocene epoch of the Neogene used more specifically with South American Land Mammal Ages. It follows the Montehermosan and precedes the Uquian
The Uquian age is a ...
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. It follows the Montehermosan and precedes the Ensenadan
The Ense ...
) 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 several ...
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 Am ...
. 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 and phorusrhacid 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 ...
'' 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
Armadillos (meaning "little armored ones" in Spanish) are New World placental mammals in the order Cingulata. The Chlamyphoridae and Dasypodidae are the only surviving families in the order, which is part of the superorder Xenarthra, alo ...
'' 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
Armadillos (meaning "little armored ones" in Spanish) are New World placental mammals in the order Cingulata. The Chlamyphoridae and Dasypodidae are the only surviving families in the order, which is part of the superorder Xenarthra, along ...