Neocynodesmus Macdonald 1963 The genus Leptocyon (Greek: leptos slender + cyon dog) includes 11 species and was the first canine.

They first appeared in North America around 34 million years ago in the Oligocene, at the same time as the Borophaginae, with whom they share features, indicating that these were two sister groups.

At the close of their genus 9 million years ago one Leptocyon lineage resembled the modern fox.

[1] Leptocyon were small-bodied, fox-like animals with a long, narrow jaw and delicate teeth.

They were probably omnivorous, feeding on small animals and fruit in a diet that remained relatively unchanged during the Miocene.