The biological order Paucituberculata contains the five 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, five species are known:
Shrewopossums are not well known because they are nocturnal—that is, they are active at night—and most inhabit inaccessible, mountainous regions.
Shrewopossums were more abundant in South America during prehistoric times, but now are confined to the alpine forests and meadows of the Andes mountains from southern Venezuela to Chile.
Shrewopossums spend most of their time on the ground, feeding on insects, spiders, grubs, and other invertebrates.
True opossums are found throughout the greater part of America from the United States to Patagonia, the number of species being largest in the more tropical parts (see Marsupialia).
The numerous cheek-teeth are crowned with minute sharply-pointed cusps, with which to crush the insects on which these creatures feed, for the opossums seem to take in South America the place in the economy of nature filled in other countries by hedgehogs, moles, shrews, andc.
The true opossums are typically represented by Didelphys marsupialis, a species, with several local races, ranging over the greater part of North America (except the extreme north).
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