Fossil range: Late Oligocene–Recent (for its Order)
Paucituberculata (pronounced /ˌpɔːsɨˌtjuːbərkj
ʊˈlɑːtə/) 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 million years 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.
Within the family of the Caenolestidae, six species are known:
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.
Genera: †Abderites - Caenolestes - Lestoros - Rhyncholestes
Caenolestidae Trouessart, 1898
Type genus: Caenolestes Thomas, 1895