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 7 genera in South America. Today, just 3 remain. They live in inaccessible forest and grassland regions of the High Andes.

Shrew or rat opossums are small, shrew-like animals, 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 spemd much of their lives in underground burrows and on surface runways.

Largely because of their rugged, inacessable 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:

• Grey-bellied Shrew Opossum , Caenolestes caniventer
• Condor Shrew Opossum , Caenolestes condorensis
• Blackish Shrew Opossum , Caenolestes convelatus
• Silky Shrew Opossum , Caenolestes fuliginosus
• Incan or Peruvian Shrew Opossum , Lestoros inca
• Chilean Shrew Opossum, Rhyncholestes raphanurus

However, Bublitz has suggested in 1987 that there might actually be two Lestoros and Rhyncholestes species (those listed here, L. gracilis and R. continentalis). This is, however, not accepted by most scientists.

See also: the magnorder Ameridelphia.