Temporal range: Late Oligocene–Recent
The order Paucituberculata // contains the seven surviving species of shrew opossum: small, shrew-like marsupials which are confined to the Andes mountains of South America. The order is thought to have diverged from the ancestral marsupial line very early. 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 three million years ago, and are currently present only in the northwestern part of the continent. Shrew opossums have lost ground to these and other placental invaders that fill the same ecological niches. Nevertheless, the ranges of shrew opossums and shrews 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 they may be more common than had been thought.
Within the family of the Caenolestidae, six species are known:
- Genus Caenolestes
- 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.
- Gardner, A.L. (2005). "Family Caenolestidae". In Wilson, D.E.; Reeder, D.M. Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. pp. 19–20. ISBN 978-0-8018-8221-0. OCLC 62265494.
- Ojala-Barbour, R. et al. (October 2013). "A new species of shrew-opossum (Paucituberculata: Caenolestide) with a phylogeny of extant caenolestids". Journal of Mammalogy 94 (5): 967–982. doi:10.1644/13-MAMM-A-018.1.