Mesonychinae

Mesonychinae is an extinct subfamily of mesonychid mammals that lived during the Paleocene and Eocene epochs. These animals were among the earliest hoofed mammals and are considered by many paleontologists to be ancestral to modern cetaceans, such as whales and dolphins. Mesonychids, including the Mesonychinae, are characterized by their large, generalized carnivorous teeth and the presence of hooves on their feet. Their dental anatomy suggests an omnivorous or carnivorous diet, though some species may have also consumed plant matter.

Members of Mesonychinae were found in North America and Eurasia. They ranged in size from relatively small, dog-like creatures to larger, wolf-like animals. A notable genus within this subfamily is Mesonyx, which gives the subfamily its name. Another important genus is Pachyaena, a larger, more robust form. Fossil evidence indicates that mesonychids were terrestrial animals, likely inhabiting forests and open woodlands. Their evolutionary position has been a subject of debate, but strong skeletal and molecular evidence now points to a close relationship with artiodactyls (even-toed ungulates) and a divergence from the lineage leading to cetaceans. The extinction of Mesonychinae occurred by the late Eocene, possibly due to competition with more specialized ungulates that evolved during that period.