Described as a distinct species in 2018, this small nocturnal marsupial was split from the Gray Mouse Opossum complex, previously considered a single species widespread across Mexico. It is endemic to the Balsas River basin in south-central Mexico, one of the country's most heavily modified tropical dry forest habitats.
A tiny, mouse-like marsupial with semi-arboreal habits, greyish fur and the prominent dark eyes typical of nocturnal marsupials. The Balsas Gray Mouse Opossum is easily confused with other species of the genus Tlacuatzin, with which it was formerly grouped. It can only be reliably distinguished from them by genetic analysis or by its location within the Balsas basin.
Tiny 5-toed tracks, featuring the opposable thumb on the hind feet characteristic of marsupials, which is absent in the rodents with which it could be confused; given its lightness, they are only clearly registered in fine dust or mud. It is usually found near fruiting bushes and rocky outcrops.
Tropical dry forest, thorn scrub and pine-oak forest in the Balsas River basin, south-central Mexico.
Mainly insects, alongside occasional small lizards, bird eggs and fruit.
Solitary, nocturnal and semi-arboreal, maintaining a very small home range; it rarely travels more than 70 m between feeding sites.
Not evaluated by the IUCN, having been described as recently as 2018 following its split from the Tlacuatzin canescens complex. Its tropical dry forest habitat is among the most heavily transformed in Mexico.
Fragmentation of the Balsas basin tropical dry forest caused by agriculture and livestock farming.
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