Thylamys velutinusvelvety fat-tailed opossum

Geographic Range

Thylamys velutinus occurs south of the Amazon Rainforest in the Brazilian states of Goiás, Minas Gerais, and São Paulo and the Distrito Federal (Carmignotto and Monfort 2006). (Carmignotto and Monfort, 2006)


Thylamys velutinus has been collected in the Cerrado (tropical savanna) ecoregion of Brazil. Like most other Thylamys species, T. velutinus appears to prefer open-canopy habitats instead of closed canopy forests. (Carmignotto and Monfort, 2006; Giarla, et al., 2010)

Physical Description

Like other members of its genus, Thylamys velutinus is notable for its incrassate (fattened) tail. The size of the tail varies by season in accordance with food availability. Although this species is a marsupial, females do not have a pouch. This species is bicolored, with darker dorsal fur and a gray ventral region. This species can be distinguished from its closest relative, Thylamys karimii, by gray hairs on its ventral region (as opposed to fully white hairs in T. karimii). Carmignotto and Monfort (2006) report head and body lengths that range from 79 to 110 mm (average 98 mm), tail lengths that range from 65 to 91 mm long (average 78 mm), and body weights that range from 13 to 35 g (average 24 g). (Carmignotto and Monfort, 2006; Giarla, et al., 2010)

  • Range mass
    13 to 35 g
    0.46 to 1.23 oz
  • Range length
    144 to 201 mm
    5.67 to 7.91 in
  • Average length
    176 mm
    6.93 in


No published studies have examined mating systems in Thylamys velutinus. However, Carmignotto and Monfort (2006) captured juvenile Thylamys karmii individuals (the closest relative to T. velutinus) in both the wet and dry season, which suggests that these species might breed year-round. (Carmignotto and Monfort, 2006; Giarla, et al., 2010)

Little is known about the reproductive behavior of Thylamys velutinus.

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual
  • viviparous

Little is known about parental investment in Thylamys velutinus. Like all marsupials, females nurse their highly altricial young. However, because members of the genus Thylamys lack a pouch (marsupium), the young must cling to their mother's venter. (Giarla, et al., 2010)

  • Parental Investment
  • altricial
  • female parental care
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female


The lifespan of this species is not known.


Little is known about the behavior of Thylamys velutinus. This species is likely solitary, as most small, insectivorous mammals are. As is the case for other members of this genus, Thylamys velutinus is likely nocturnal and probably enters torpor during the day.

Home Range

The home range of this species is not known.

Communication and Perception

Because this species is small and nocturnal, communication between individuals is likely primarily olfactory in nature. Palma (1997) reports that the olfactory and visual regions of another Thylamys species' brain are especially well developed. (Palma, 1997)

Food Habits

Little is known about the food habits of this species. Like other Thylamys species, Thylamys velutinus likely consumes insects and perhaps occasionally eats small vertebrates, leaves, fruit, seeds, and carrion (Palma 1997). (Palma, 1997)


Like other small mammals, Thylamys velutinus is likely well adapted to avoiding predators by being nocturnal and inconspicuous. No records of known predators are available.

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Thylamys velutinus likely acts as an important predator to many arthropod species and perhaps some small vertebrates. It is likely prey to both bird and medium-sized mammals, such as owls and foxes. It is also likely host to many ecto- and endoparasites. More specific information about the ecosystem role of Thylamys velutinus is not presently available.

Economic Importance for Humans: Positive

There are no known positive impacts of Thylamys velutinus on humans.

Economic Importance for Humans: Negative

There are no known negative effects of Thylamys velutinus.

Conservation Status

Thylamys velutinus is currently listed under "Least Concern" on the IUCN Red List.


Tom Giarla (author), University of Minnesota, Sharon Jansa (editor), American Museum of Natural History, Robert Voss (editor), American Museum of Natural History, Tanya Dewey (editor), University of Michigan-Ann Arbor.



living in the southern part of the New World. In other words, Central and South America.

World Map


uses sound to communicate


young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.


Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


an animal that mainly eats meat


uses smells or other chemicals to communicate


having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.


animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females


An animal that eats mainly insects or spiders.


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


active during the night


reproduction that includes combining the genetic contribution of two individuals, a male and a female


lives alone


uses touch to communicate


Living on the ground.


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.


A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.


movements of a hard surface that are produced by animals as signals to others


uses sight to communicate


reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.


Carmignotto, A., T. Monfort. 2006. Taxonomy and distribution of the Brazilian species of Thylamys (Didelphimorphia: Didelphidae). Mammalia, 70: 126–144.

Giarla, T., R. Voss, S. Jansa. 2010. Species Limits and Phylogenetic Relationships in the Didelphid Marsupial Genus Thylamys Based on Mitochondrial DNA Sequences and Morphology. Bulletin of the American Museum of Natural History, 346: 1-67.

Palma, R. 1997. Thylamys elegans. Mammalian Species, 572: 1-4.