Common Fat-tailed Mouse Opossum vs Humpback smooth hound

Thylamys pusillus compared with Mustelus whitneyi

Key Differences

• Common Fat-tailed Mouse Opossum is Least Concern while Humpback smooth hound is Critically Endangered.

Taxonomic Classification

Rank	Common Fat-tailed Mouse Opossum	Humpback smooth hound
Kingdom same	Animalia (Animals)	Animalia (Animals)
Phylum same	Chordata (Chordates)	Chordata (Chordates)
Class	Mammalia (Mammals)	Chondrichthyes (Cartilaginous Fish)
Order	Didelphimorphia (Didelphimorphia)	Carcharhiniformes (Ground Sharks)
Family	Didelphidae	Triakidae
Genus	Thylamys	Mustelus
Species	Thylamys pusillus	Mustelus whitneyi

Evolutionary Relationship

Common Fat-tailed Mouse Opossum and Humpback smooth hound share a common ancestor at the Phylum level: Chordata. (Chordates)

Conservation Status

Common Fat-tailed Mouse Opossum

LC — Least Concern

Humpback smooth hound

CR — Critically Endangered

Physical Characteristics

Attribute	Common Fat-tailed Mouse Opossum	Humpback smooth hound
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Common Fat-tailed Mouse Opossum

Habitat

Typically found in diverse terrestrial and aquatic ecosystems.

Humpback smooth hound

Habitat

Found across multiple habitat types including temperate broadleaf and mixed forests, temperate grasslands and steppes, and montane grasslands and shrublands, among 5 distinct biome types within the Neotropic biogeographic realm.

Range

Found in Chile. Currently classified as Critically Endangered on the IUCN Red List, this species faces significant conservation challenges across its range.

Common Fat-tailed Mouse Opossum

The Common Fat-tailed Mouse Opossum (<em>Thylamys pusillus</em>) is a small marsupial belonging to the genus Thylamys within the family Didelphidae. Like other members of its genus, this species typically stores fat in its tail, which becomes swollen during periods of food abundance and is metabolised during leaner times, a physiological adaptation that provides energy reserves. <em>Thylamys pusillus</em> is generally found in diverse terrestrial and aquatic ecosystems, often in dry woodlands, scrublands, and grassland habitats of South America. The species is assessed as Least Concern on the IUCN Red List, indicating it is not currently considered at risk of extinction. Detailed geographic range data are not available in the current record, but members of this genus are typically distributed across parts of Argentina, Bolivia, Paraguay, and Uruguay. Biological traits including average lifespan, body dimensions, and specific dietary composition remain poorly documented in the scientific literature, though Thylamys species are generally considered omnivorous, often consuming insects, small vertebrates, and plant material.