Common Fat-tailed Mouse Opossum vs Common Rustgill

Thylamys pusillus compared with Gymnopilus penetrans

Taxonomic Classification

Rank	Common Fat-tailed Mouse Opossum	Common Rustgill
Kingdom	Animalia (Animals)	Fungi (Fungi)
Phylum	Chordata (Chordates)	Basidiomycota (Club Fungi)
Class	Mammalia (Mammals)	Agaricomycetes (Mushrooms)
Order	Didelphimorphia (Didelphimorphia)	Agaricales (Gilled Mushrooms)
Family	Didelphidae	Hymenogastraceae
Genus	Thylamys	Gymnopilus
Species	Thylamys pusillus	Gymnopilus penetrans

Conservation Status

Common Fat-tailed Mouse Opossum

LC — Least Concern

Common Rustgill

LC — Least Concern

Physical Characteristics

Attribute	Common Fat-tailed Mouse Opossum	Common Rustgill
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Common Fat-tailed Mouse Opossum

Habitat

Typically found in diverse terrestrial and aquatic ecosystems.

Common Rustgill

Habitat

Typically found in forest floors, decomposing wood, and soil ecosystems.

Range

Distributed across Belgium, Denmark, Norway, Portugal, and Sweden.

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.

Common Rustgill

<em>Gymnopilus penetrans</em>, the common rustgill, is a saprotrophic basidiomycete fungus in the family Hymenogastraceae, commonly found across temperate regions of Europe and beyond. It has been recorded in Belgium, Denmark, Norway, Portugal, and Sweden, typically fruiting on decaying conifer wood, stumps, buried roots, and woody debris in forests and woodland habitats. The fruiting bodies are small to medium-sized mushrooms with tawny orange to rust-brown caps, typically 2–7 centimeters in diameter, and bright rusty-orange gills that give the species its common name. The stem is similarly colored and typically fibrous. As a wood-decaying fungus, common rustgill plays an important ecological role in the decomposition of dead conifer timber and the recycling of nutrients in forest ecosystems. The species produces minute, roughened, rusty-brown spores. It is assessed as Least Concern on the IUCN Red List. The common rustgill typically fruits from late summer through autumn. It may occasionally be confused with related <em>Gymnopilus</em> species; some members of the genus contain potentially toxic or psychoactive compounds, though <em>G. penetrans</em> is generally considered of low toxicity. Biological traits such as average lifespan and detailed dietary substrate specificity remain poorly documented in comprehensive ecological databases.