The

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Caenolestidae contains the seven surviving species of shrew opossum: small,

shrew Shrews ( family Soricidae) are small mole-like mammals classified in the order Eulipotyphla. True shrews are not to be confused with treeshrews, otter shrews, elephant shrews, West Indies shrews, or marsupial shrews, which belong to dif ...

-like

marsupial Marsupials are a diverse group of mammals belonging to the infraclass Marsupialia. They are natively found in Australasia, Wallacea, and the Americas. One of marsupials' unique features is their reproductive strategy: the young are born in a r ...

s that are confined to the

Andes The Andes ( ), Andes Mountains or Andean Mountain Range (; ) are the List of longest mountain chains on Earth, longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range ...

mountains of

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

. The order is thought to have diverged from the ancestral marsupial line very early. They were once included in the superorder but it is now known that Ameridelphia is

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

, having given rise to

Australidelphia Australidelphia is a superorder of marsupials encompassing about three-quarters of all living marsupial species, including all those native to Australasia and one South American species, the monito del monte. Unlike other American marsupials, wh ...

, and thus could be considered an

evolutionary grade A grade is a taxon united by a level of morphological or physiological complexity. The term was coined by British biologist Julian Huxley, to contrast with clade, a strictly phylogenetic unit. Phylogenetics The concept of evolutionary grades ...

. Genetic studies indicate that they are the second most basal order of marsupials, after the didelphimorphs. As recently as 20 million years ago, at least seven genera were in South America. Today, just three genera remain. They live in inaccessible forest and grassland regions of the High Andes. Shrews were entirely absent from South America until the

Great American Interchange The Great American Biotic Interchange (commonly abbreviated as GABI), also known as the Great American Interchange and the Great American Faunal Interchange, was an important late Cenozoic paleozoogeographic biotic interchange event in which land ...

three million years ago, and are currently present only in the northwestern part of the continent. Traditionally, it was thought that shrew opossums lost ground to these and other

placental Placental mammals (infraclass Placentalia ) are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguished ...

invaders that fill the same

ecological niche In ecology, a niche is the match of a species to a specific environmental condition. Three variants of ecological niche are described by It describes how an organism or population responds to the distribution of Resource (biology), resources an ...

s. Evidence suggests, however, that both groups not only overlap, but do not seem to be in direct competition, and the marsupials' larger size seems to imply that they prey on shrews and rodents. Several opossums, such as '' Monodelphis'', also occupy small insectivore niches. Shrew opossums (also known as rat opossums or caenolestids) are about the size of a small rat (9–14 cm long), with thin limbs, a long, pointed snout and a slender, hairy tail. They are largely carnivorous, being active hunters of

insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...

earthworm An earthworm is a soil-dwelling terrestrial invertebrate that belongs to the phylum Annelida. The term is the common name for the largest members of the class (or subclass, depending on the author) Oligochaeta. In classical systems, they we ...

s, and small vertebrates. They have small eyes and poor sight, and hunt in the early evening and at night, using their hearing and long, sensitive

whisker Whiskers, also known as vibrissae (; vibrissa; ) are a type of stiff, functional hair used by most therian mammals to sense their environment. These hairs are finely specialised for this purpose, whereas other types of hair are coarser as t ...

s to locate prey. They seem to spend much of their lives in burrows and on surface runways. Like several other marsupials, they do not have a pouch, and it appears that females do not carry the young constantly, possibly leaving them in the burrow. Largely because of their rugged, inaccessible habitat, they are very poorly known and have traditionally been considered rare. Several ecological factors, including density of forest, contribute to the part of the forests the shrew opossums occupy. Recent studies suggest they may be more common than had been thought. Their

karyotype A karyotype is the general appearance of the complete set of chromosomes in the cells of a species or in an individual organism, mainly including their sizes, numbers, and shapes. Karyotyping is the process by which a karyotype is discerned by de ...

has also been described through contemporary research in order to better understand this organism.

Classification

* Genus ''

Caenolestes The common shrew opossums (genus ''Caenolestes'') are members of the family Caenolestidae. They are found in Colombia, Ecuador, Peru, and Venezuela. The most recently discovered species is ''C. sangay''. Phylogeny See also * List of mammal ...

'' Thomas 1895 ** ''C. caniventer'' ( Gray-bellied caenolestid) ** ''C. condorensis'' ( Andean caenolestid) ** ''C. convelatus'' ( Northern caenolestid) ** ''C. fuliginosus'' ( Dusky caenolestid) ** ''C. sangay'' ( Eastern caenolestid) * Genus †'' Caenolestoides'' Arbello, Martin & Cardoso 2021 ** †''C. miocaenicus'' Arbello, Martin & Cardoso 2021 * Genus †'' Gaimanlestes'' Arbello, Martin & Cardoso 2021 ** †''G. pascuali'' Arbello, Martin & Cardoso 2021 * Genus '' Lestoros'' Oehser 1934 ** ''L. inca'' (Peruvian or Incan caenolestid) * Genus †'' Pliolestes'' Reig 1955 ** †''P. tripotamicus'' Reig 1955 ** †''P. venetus'' Goin, Montalvo & Visconti 2000 * Genus †'' Pseudhalmarhiphus'' Ameghino 1903 ** †''P. guaraniticus'' (Ameghino 1899) Ameghino 1903 * Genus '' Rhyncholestes'' Osgood 1924 ** ''R. raphanurus'' ( Long-nosed caenolestid) * Genus †'' Stilotherium'' Ameghino 1887 ** †''S. parvum'' Arbello, Martin & Cardoso 2021 ** †''S. dissimile'' Ameghino 1887 However, Bublitz suggested in 1987 there were actually two ''Lestoros'' and ''Rhyncholestes'' species (those listed here plus ''L. gracilis'' and ''R. continentalis''). This is, however, not accepted by most scientists.

Fossils

Spatio-temporal locations of fossil species:Caenolestidae
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

Paleogene

;Eocene * '' Perulestes'' - Pozo Formation, Peru ;Barrancan * '' Progarzonia notostylopense'' -

Sarmiento Formation The Sarmiento Formation (Spanish language, Spanish: ''Formación Sarmiento''), in older literature described as the Casamayor Formation, is a geological formation in Chubut Province, Argentina, in central Patagonia, which spans around 30 million y ...

, Argentina ;

Deseadan The Deseadan () age is a period of geologic time (29.0–21.0 Ma) within the Oligocene epoch of the Paleogene to the Early Miocene epoch of the Neogene, used more specifically within the SALMA classification of South America. It follows the Tingu ...

* '' Pseudhalmarhiphus guaraniticus'' -

, Argentina

Neogene

; Colhuehuapian *

Pebas Formation The Pebas Formation is a stratigraphic unit#Lithostratigraphic units, lithostratigraphic unit of Miocene age, found in western Amazon rainforest, Amazonia. The geological formation, formation extends over , including parts of Brazil, Peru, Ecuador ...

, Amazon Basin * '' Caenolestoides miocaenicus'' -

, Colhue-Huapi Member * '' Gaimanlestes pascuali'' -

, Trelew Member * '' Stilotherium parvum'' -

, Colhue-Huapi Member ;

Laventan The Laventan () age is a period of geologic time (13.8 to 11.8 Ma) within the Middle Miocene epoch of the Neogene, used more specifically within the SALMA classification in South America. It follows the Colloncuran and precedes the Mayoan age. ...

* Honda Group, Bolivia ;

Huayquerian The Huayquerian () age is a period of geologic time (9.0–6.8 Ma) within the Late Miocene epoch of the Neogene, used more specifically within the SALMA classification. It follows the Chasicoan and precedes the Montehermosan age. Etymology T ...

* '' Pliolestes venetus'' - Cerro Azul Formation, Argentina ;Pliocene * Umala Formation, Bolivia ;

Montehermosan The Montehermosan age is a period of geologic time (6.8–4.0 Mya (unit), Ma) within the Miocene and Pliocene epochs of the Neogene used more specifically with South American Land Mammal Ages. It follows the Huayquerian and precedes the Chapadmalal ...

* '' Pliolestes tripotamicus'' - Argentina

References

{{DEFAULTSORT:Shrew Opossum Priabonian first appearances Mammals of the Andes Paleogene mammals of South America Deseadan Paleogene Argentina Fossils of Argentina Paleogene Peru Fossils of Peru Neogene mammals of South America Colhuehuapian Laventan Montehermosan Huayquerian Neogene Argentina Neogene Bolivia Fossils of Bolivia Quaternary mammals of South America Mammals described in 1898 Taxa named by Édouard Louis Trouessart