Physical characteristics

Abrocoma have large eyes and ears on an elongated head. The ears are round rather than pointed. However, the nose assumes the typical long and pointed rat-like countenance. The cylindrical tail is covered by short and fine hairs, unlike the bushier and squirrel-like tail of true chinchillas. Another distinguishing feature is the double pair of nipples present on the upper belly of females.

Members of the genus Abrocoma have four digits on the forelimbs and five digits on the hindlimbs. Soles are uncov-

A captive ashy chinchilla rat (Abrocoma cinerea). (Photo by Dr. R. E. Martin/Mammal Images Library of the American Society of Mam-mologists.)

ered, while the tops of the feet are fur-covered. Small claws are present on the fore and hind feet. The claws are not exceptionally powerful, owing to their hollow structure. However, some stiffness is provided in the middle three toes of the hind feet by protruding upper hairs that act to form a grooming or utility comb.

Chinchilla rats are covered in fur that is gray or gray-brown in color. The belly is yellowish white or brown. The silky, thick fur resembles that of the highly prized fur of the family Chinchillidae, but is not as woolly in texture. Indeed, chinchilla rats are a source of false fur sold to unsuspecting buyers by unscrupulous merchants.

For its size, the members of Abrocoma possess a long intestinal tract. The combined small and large intestines coil for 8.2 ft (2.5 m), and the caecum extends for a further 7.9 in (20 cm). The intestines and other internal organs are well protected by the 17 pairs of ribs. No other rodent has as many ribs.

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