paramyids

Paramyids were an extinct group of early placental mammals that lived during the Paleocene and Eocene epochs. They are notable for being among the most successful and diverse mammal groups of that era. Fossil evidence suggests paramyids were widespread across North America, Europe, and Asia. Their diet likely varied, with some species adapted to herbivory and others to omnivory.

The exact taxonomic position of paramyids has been a subject of debate among paleontologists. Historically, they were often placed within the order Rodentia, due to superficial similarities in their dentition, particularly the presence of ever-growing incisors. However, more recent analyses, incorporating a broader range of anatomical and molecular evidence, have led to their classification in a separate order, Paramyida. This order is now considered to be a basal lineage within the Euarchontoglires superorder, which also includes rodents, lagomorphs, primates, and dermopterans.

Paramyids displayed a range of sizes, from small, shrew-like creatures to animals comparable to modern rabbits or small marmots. Their skeletal structure suggests they were generally terrestrial, though some may have been adept climbers or swimmers. The fossil record indicates a gradual evolutionary radiation of paramyids, with numerous genera and species identified, showcasing adaptations to different ecological niches. The eventual decline and extinction of paramyids is not fully understood, but likely involved competition with the evolving rodents, which eventually diversified and came to dominate the rodent niche.