Testiosallus

Testiosallus is an extinct genus of small mammal known from fragmentary fossils found in early Eocene deposits of Central Asia. The genus currently includes a single described species, Testiosallus centralis. It was established in a 2010 description based on isolated teeth and partial jaw elements.

Anatomical evidence suggests a small animal, with estimates of body mass around 80–120 grams. The dentition features sharp cusps on premolars and molars, with wear indicating an insectivorous diet, possibly supplemented by fruit. Postcranial remains are sparse, but limb fragments imply an agile creature capable of climbing and maneuvering in a forested environment.

The phylogenetic position of Testiosallus is uncertain. Some analyses place it near the base of Placentalia with unclear affinities; others suggest it represents an early, stem therian lineage. The limited material means robust phylogenetic placement remains elusive.

Geography and dating: Fossils derive from sedimentary formations in Central Asia, dating to the early Eocene, approximately 52–50 million years ago. The available record suggests Testiosallus may have been endemic to this region during that interval.

Significance: Testiosallus contributes to understanding early mammal diversification in Eurasia and illustrates the fragmentary nature of the early Eocene fossil record. Additional discoveries would help clarify its anatomy, ecology, and evolutionary relationships.