Shrew opossum

Taxobox
name = Shrew opossums

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image_width = 240px
fossil_range = Late Oligocene - Recent (for its Order)
regnum = Animalia
phylum = Chordata
classis = Mammalia
infraclassis = Marsupialia
ordo = Paucituberculata
ordo_authority = Ameghino, 1894
familia = Caenolestidae
familia_authority = Trouessart, 1898
subdivision_ranks = Genera
subdivision = "Caenolestes"
"Lestoros"
"Rhyncholestes"

The biological order Paucituberculata contains the six surviving species of shrew opossum: small, shrew-like marsupials which are confined to the Andes mountains of South America. It is thought that the order diverged from the ancestral marsupial line very early. As recently as 20 million years ago, there were at least seven genera in South America. Today, just three genera remain. They live in inaccessible forest and grassland regions of the High Andes. Insectivores were entirely absent from South America until the Great American Interchange three Ma ago, and are currently present only in the northwestern part of the continent. Shrew opossums have lost ground to the these and other placental invaders that fill the same ecological niches. Nevertheless, the ranges of shrew opossums and insectivores overlap broadly.

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 insects, earthworms 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 whiskers to locate prey. They seem to spend much of their lives in underground burrows and on surface runways.

Largely because of their rugged, inaccessible habitat, they are very poorly known and have traditionally been considered rare. Recent studies suggest that they may be more common than had been thought.

Classification

Within the family of the Caenolestidae, six species are known:

* Genus "Caenolestes"
** Grey-bellied Shrew Opossum, "Caenolestes caniventer"
** Andean Shrew Opossum, "Caenolestes condorensis"
** Northern Shrew Opossum, "Caenolestes convelatus"
** Dusky Shrew Opossum, "Caenolestes fuliginosus"
* Genus "Lestoros"
** Peruvian or Incan Shrew Opossum, "Lestoros inca"
* Genus "Rhyncholestes"
** Long-nosed Shrew Opossum, "Rhyncholestes raphanurus"

However, Bublitz suggested in 1987 that 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.

References

*MSW3 Gardner|pages=19-20