The

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

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 different fa ...

-like

marsupial Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a po ...

s that are confined to the

Andes The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...

mountains of

South 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 southe ...

. 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 In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

, having given rise to

Australidelphia Australidelphia is the superorder that contains roughly three-quarters of all marsupials, including all those native to Australasia and a single species — the monito del monte — from South America. All other American marsupials are members of ...

, 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. Definition An evolutionary grade is a group of ...

. Genetic studies indicate that they are the second most basal order of marsupials, after the

didelphimorph 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 ...

s. 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 lan ...

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 Marsupial Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsup ...

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 resources and competitors (for ...

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 ''Monodelphis'' is a genus of marsupials in the family Didelphidae, commonly referred to as short-tailed opossums. They are found throughout South America. , the most recently described species is ''M. vossi''. Species * Sepia short-tailed o ...

'', 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 pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...

earthworm An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; and they usually have setae on all segments. Th ...

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 Vibrissae (; singular: vibrissa; ), more generally called Whiskers, are a type of stiff, functional hair used by mammals to sense their environment. These hairs are finely specialised for this purpose, whereas other types of hair are coarser ...

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 metaphase 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 disce ...

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

Classification

Within the family of the Caenolestidae, seven extant species are known: * Genus ''

Caenolestes The common shrew opossums (genus ''Caenolestes'') are members of the family Caenolestidae. They are found in Colombia, Ecuador, Peru, and Venezuela Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República ...

'' ** Gray-bellied caenolestid, ''Caenolestes caniventer'' ** Andean caenolestid, ''Caenolestes condorensis'' ** Northern caenolestid, ''Caenolestes convelatus'' ** Dusky caenolestid, ''Caenolestes fuliginosus'' **

Eastern caenolestid The eastern caenolestid (''Caenolestes sangay'') is a shrew opossum found on the eastern slopes of the Andes in southern Ecuador. Etymology The origin of the genus name (''Caenolestes'') drives from the Greek words ''kainos'' ("new") and ''lest ...

, ''Caenolestes sangay'' * Genus '' Lestoros'' ** Peruvian or Incan caenolestid, ''Lestoros inca'' * Genus '' Rhyncholestes'' ** Long-nosed caenolestid, ''Rhyncholestes raphanurus'' 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.

Fossil species

Additionally, species from the fossil record are known:Caenolestidae
at

Fossilworks Fossilworks is a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database The Paleobiology Database is an online resource for information on the distribution and classification of fossil animals ...

.org

Paleogene

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

Sarmiento Formation The Sarmiento Formation (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 years from the mid- ...

, Argentina ;

Deseadan The Deseadan ( es, Deseadense) 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 fo ...

* '' Pseudhalmarhiphus guaraniticus'' -

, Argentina

Neogene

;

Colhuehuapian The Colhuehuapian age is a period of geologic time (21.0–17.5 Ma) within the Early Miocene epoch of the Neogene, used more specifically within the SALMA classification in South America. It follows the Deseadan and precedes the Santacrucian ag ...

Pebas Formation The Pebas Formation is a lithostratigraphic unit of Miocene age, found in western Amazonia. The formation extends over , including parts of Brazil, Peru, Ecuador and Colombia.Wesselingh et al., 2006 It is interpreted as representing the deposits ...

, Amazon Basin * '' Caenolestoides miocaenicus'' Arbello, Martin & Cardoso, 2021 -

, Colhue-Huapi Member * '' Gaimanlestes pascuali'' Arbello, Martin & Cardoso, 2021 -

, Trelew Member * '' Stilotherium parvum'' Arbello, Martin & Cardoso, 2021 -

, Colhue-Huapi Member ;

Laventan The Laventan ( es, Laventense) 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 ...

* Honda Group, Bolivia ;

Huayquerian The Huayquerian ( es, Huayqueriense) 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 Mayoan and precedes the Montehermosan age. ...

* '' Pliolestes venetus'' -

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 ;Pliocene *

Umala Formation Umala is a location in La Paz in Bolivia. It is the seat of the Umala Municipality, the second municipal section of the Aroma Province Aroma is one of the twenty provinces of the Bolivian La Paz Department. It is situated in the southern pa ...

, Bolivia ;

Montehermosan The Montehermosan age is a period of geologic time (6.8–4.0 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 Chapadmalalan The C ...

* '' Pliolestes tripotamicus'' - Argentina

References

{{DEFAULTSORT:Shrew Opossum Priabonian first appearances Marsupials of South America 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