Leptocyon
The genus Leptocyon includes 11 species and is the oldest known canine. They were small and weighed around. 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. Borophaginae skull and dentition were designed for a powerful killing bite compared with the Leptocyon which were designed for snatching small, fast-moving prey. The species L. delicatus is the smallest canid to have existed. At the close of their genus 9 million years ago one Leptocyon lineage resembled the modern fox.
File:Fossil red fox skull compared to Leptocyon vafer skull cast .jpg|left|thumb|L. vafer skull cast of a specimen from California, compared to a red fox skull. At the American [Museum of Natural History|AMNH].
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.