Thylamys karimii (Petter, 1968)

Russell A. Mittermeier & Don E. Wilson, 2015, Didelphidae, Handbook of the Mammals of the World – Volume 5 Monotremes and Marsupials, Barcelona: Lynx Edicions, pp. 129-186 : 175

publication ID


persistent identifier

treatment provided by


scientific name

Thylamys karimii


77. View Plate 9: Didelphidae

Karimi’s Fat-tailed Opossum

Thylamys karimii

French: Opossum de Karimi / German: Karimis Fettschwanzbeutelratte / Spanish: Marmosa coligruesa de Karimi

Other common names: Karimi’s Fat-tailed Mouse Opossum, Karimi’s Thylamys

Taxonomy. Marmosa karimii Petter, 1968 ,

“ région d’Exu , Pernambuco, Brazil.”

This species is monotypic.

Distribution. C & NE Brazil (Rondonia, Mato Grosso, Tocantins, Piaui, Pernambuco, Bahia, Goias, and Minas Gerais). View Figure

Descriptive notes. Head-body 7.9-12.9 cm, tail 6:9-10.6 cm; weight 16-43 g. Karimi’s Fat-tailed Opossum has brownish dorsal fur, with abundant four-color banded hairs, gray at bases, then brownish, then cream, and with dark tips. There are also sparse, gray-based, dark-tipped, long guard hairs. Body sides are slightly paler, with fewer but brighter guard hairs; banded hairs lack brownish band. Tricolored pattern typical of most species of Thylamys is inconspicuous in some specimens but clear in others, with a clear transition from mid-dorsal to lateral color. Head is colored as dorsum on crown and brighter in mid-rostral region, with creamy-white-based, dark-tipped hairs and three-color banded hairs (gray-based, creamy, and dark-tipped). Narrow brownish mid-rostral streak is usually present, and there are very narrow brownish eye-rings that extend to, but do not reach, nose or bases of ears. Tail length is ¢.85% of head-body length, and tail is proximally furred for less than 10 mm,slightly bicolored. When tail is incrassated (enlarged with stored fat), it reaches 3-5-5-5 mm in diameter. Ventral fur is creamy-white from chin and cheeks to inguinal region, with lateral bands of gray-based, creamy-white-tipped hairs that are usually faint and narrow but occasionally conspicuous, 3-8 mm width. Throat gland is present in both sexes. Fur is dense, short (3—4 mm) ventrally and longer (6-7 mm) dorsally, with even longer (8-9 mm) guard hairs. Forefeet and hindfeet are whitish, forelimbs are creamy-white dorsally and ventrally, hindlimbs are brownish dorsally and creamy-white ventrally, and ears are uniformly brownish and appear naked. Females lack a pouch, and nine mammae are present, four on each side and a medial mamma, or five on one side and four on the other without a medial mammal. Karimi’s Fat-tailed Opossum has a 2n = 14, FN = 24 karyotype, with all biarmed autosomes, and a biarmed X-chromosome and an acrocentric Y-chromosomes. An FN = 20 karyotype has also been reported. Skull size is sexually dimorphic.

Habitat. Open habitats in cerrado and caatinga, including grasslands, shrubby vegetation, dry forests, and savanna formations.

Food and Feeding. The type specimen of Karimi’s Fat-tailed Opossum, while kept in captivity, was kept alive on a diet including small birds, insects, chopped meat, mealworms, bananas, juicy fruits, and sweet biscuits. Its natural diet is unknown. Some observations reported for Karimi’s Fat-tailed Opossum were actually based on misidentified Agile Opossum ( Gracilinanus agilis ) and Agricola’s Opossum ( Cryptonanus agricolai ).

Breeding. Lactating female Karimi’s Fat-tailed Opossums were captured in the wet season (January-April), and juveniles were collected in dry and wet seasons, although more frequently in the dry season.

Activity patterns. Karimi’s Fat-tailed Opossum is apparently nocturnal. The captive type specimen was highly active at night and lethargic during the day when a drop in body temperature to about room temperature (c.20-25°C) was noted. It did not, however, survive a quick temperature drop to 15°C.

Movements, Home range and Social organization. The type specimen of Karimi’s Fattailed Opossum was captured inside a shallow dead-end burrow that may have been an abandoned lizard burrow. While kept in captivity for five months, it only moved on the ground and did not attempt to climb any bush.

Status and Conservation. Classified as Vulnerable on The IUCNN Red List. Karimi’s Fattailed Opossum has been assigned this status based on inferred rates of population decline derived from rates of habitat loss. Cerrado has been intensively deforested for conversion to large-scale agro-industrial monoculture (e.g. soy bean farming), which is threatening all species restricted to this region.

Bibliography. Astua (2010), Bonvicino et al. (2012), Carmignotto & Aires (2011), Carmignotto & Monfort (2006), Carvalho, Oliveira & Mattevi (2009), Carvalho, Oliveira, Nunes & Mattevi (2002), Creighton & Gardner (2007c), Giarla & Jansa (2014), Giarla et al. (2010), Melo & Sponchiado (2012), Palma, A.R.T. & Vieira (2012), Palma, R.E. et al. (2014), Petter (1968), Streilein (1982b).














Thylamys karimii

Russell A. Mittermeier & Don E. Wilson 2015

Marmosa karimii

Petter 1968