''Thylamys'' 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 n ...

opossum 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 ...

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 mammal has ...

e are rounded rather than pointed. The females lack a

pouch Pouch may refer to: * A small bag such as a packet (container), teabag, money bag, sporran, fanny pack, etc. * Marsupium (disambiguation), especially pouch (marsupial), an anatomical feature in which young are carried * Cadaver pouch, a bod ...

. The females'

nipple The nipple is a raised region of tissue on the surface of the breast from which, in females, milk leaves the breast through the lactiferous ducts to feed an infant. The milk can flow through the nipple passively or it can be ejected by smooth ...

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 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 means "less recent" ...

, with the oldest specimens being found in 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 ...

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, t ...

and the Honda Group of Colombia. 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 is 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 cre ...

.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