''Thylamys'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

opossum Opossums () are members of the marsupial order Didelphimorphia () endemic to the Americas. The largest order of marsupials in the Western Hemisphere, it comprises 126 species in 18 genera. Opossums originated in South America and entered North A ...

s in the family Didelphidae. The

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammals h ...

e are rounded rather than pointed. The females lack a pouch. The females'

nipple The nipple is a raised region of tissue on the surface of the breast from which, in lactating females, breast milk, milk from the mammary gland leaves the body through the lactiferous ducts to Breastfeeding, nurse an infant. The milk can flow th ...

s are arranged in two symmetrical rows on the abdomen. All species but ''T. macrurus'' store fat in their tails, although this is not necessarily true for all species in the genus. Fossils belonging to the genus date back to the

Miocene The Miocene ( ) is the first epoch (geology), 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 mea ...

, with the oldest specimens being found in the Cerro Azul Formation of

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

and the Honda Group of

Colombia Colombia, officially the Republic of Colombia, is a country primarily located in South America with Insular region of Colombia, insular regions in North America. The Colombian mainland is bordered by the Caribbean Sea to the north, Venezuel ...

. Genetic studies indicate that the genus may have originated around 14 million years ago.

Taxonomy

Cladogram of living ''Thylamys'' species. Other species of ''Thylamys''.''Thylamys''
at

Fossilworks Fossilworks was a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database, a large relational database assembled by hundreds of paleontologists from around the world. History Fossilworks was cr ...

.org * †''T. colombianus'' * '' T. fenestrae'' * †''T. minutus'' * †''T. pinei'' * †''T. zettii''

References

Opossums Marsupial genera Neogene animals of South America Quaternary animals of South America Lujanian Ensenadan Uquian Chapadmalalan Montehermosan Huayquerian Chasicoan Mayoan Laventan Colloncuran Taxa described in 1843 Taxa named by John Edward Gray Taxonomy articles created by Polbot {{marsupial-stub