Osishinia

Osishinia is a genus of small, extinct mammals that lived during the Eocene epoch, approximately 56 to 34 million years ago. The genus is known from a single species, Osishinia minor, which was discovered in the Green River Formation of Wyoming, USA. Osishinia is notable for its small size, with the holotype specimen measuring only about 1.5 inches (3.8 cm) in length.

Osishinia is classified within the order Rodentia, but its exact placement within the rodent family tree remains uncertain. It is often considered a basal rodent, meaning it is one of the earliest diverging lineages within the order. This is suggested by its primitive dental and skeletal features, which are more similar to those of early rodents than to those of more derived rodents.

The genus name Osishinia is derived from the Osishin Member of the Green River Formation, where the fossil was found, and the Greek word "nia," meaning "dwarf," reflecting the small size of the animal. The specific epithet minor means "small" in Latin.

Osishinia provides valuable insights into the early evolution of rodents, helping scientists understand the origins and diversification of this diverse group of mammals. Despite its small size and limited fossil record, Osishinia plays an important role in our understanding of rodent evolution.