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Shrew opossums Fossil range: Late Oligocene - Recent (for its Order)
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Infraclass: Marsupialia Order: Paucituberculata Ameghino, 1894 Family: Caenolestidae Trouessart, 1898
Genera
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. These shrew opossums fill the same ecological niche, but have lost ground to the placental invaders. Nevertheless, the ranges of the two groups overlap broadly.

Shrew opossums (also known as rat opossums) 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.

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.

• Gardner, Alfred (November 16, 2005). in Wilson, D. E., and Reeder, D. M. (eds): Mammal Species of the World, 3rd edition, Johns Hopkins University Press, 19-20. ISBN 0-801-88221-4.