Dichobune

Dichobune is the type genus of the Dichobunoidea, an extinct paraphyletic superfamily consisting of some of the earliest artiodactyls known in the fossil record. It was a primitive artiodactyl genus that was endemic to western Europe and lived from the Middle Eocene (or possibly the Early Eocene) to the Early Oligocene. The type species Dichobune leporina was originally described as a species belonging to Anoplotherium beginning in 1804 by the French naturalist Georges Cuvier, who noted its small size. Cuvier assigned it to its own subgenus Dichobune in 1822; later naturalists promoted it to genus rank and observed that it was not close to the Anoplotheriidae as previously thought. Today, there are five valid species within Dichobune.

Dichobune has a somewhat elongated skull with a lengthy snout (with the snout of D. jehennei being particularly lengthy), large and semi-centred orbits, and a complete dentition of 44 teeth (the maximum in placental mammals), which mainly consists of brachyodont (low-crowned) and bunodont (round-cusped) cheek teeth. Its dental morphologies suggest that it could have had a frugivorous diet, meaning that leaves were probably only a minor component of its diet compared to the likes of fruits and seeds. Its foot morphology was primitive with unfused foot bones including a total of four digits each, only two middle ones of which are functional for didactyl (two-toed) movements. Dichobunoids were generally small mammals, especially in comparison to modern artiodactyls, but Dichobune was medium-sized in comparison to its close relatives. Earlier species of Dichobune were smaller-sized while some later species were larger, with the late-appearing D. jehennei being the largest species of the genus.

The European subfamily Dichobuninae made its appearance by the Early to Middle Eocene, with D. aff. robertiana being among the earliest representatives. During much of its existence, western Europe was an archipelago that was isolated from the rest of Eurasia, meaning that Dichobune lived in a tropical-subtropical environment with various other animals that also evolved with strong levels of endemism. It survived multiple faunal turnover events within Europe, including the large Grande Coupure extinction event that drove many of its close relatives to extinction and replaced them with immigrant faunas from eastern Eurasia. Its existence in the Early Oligocene was not particularly long, but it likely descended into Metriotherium, a dichobunid that lasted up to the Late Oligocene and briefly coexisted with it.