Diacodexis is an extinct genus of small herbivorous mammals belonging to the family Diacodexeidae[1][2][3] that lived in North America, Europe and Pakistan from 55.4 mya to 46.2 mya and existing for approximately 9.2 million years.

In life, it would have resembled a modern duiker, measuring about 50 centimetres (1.6 ft) in body length, but with a much longer tail.

[4] D. ilicis possessed a very simple neocortex, characterised by an almond-shaped gyrus instead of parallel sulci as some earlier authors had believed.

[5] As suggested by its long legs, Diacodexis is believed to have been fast-running, capable of leaping relatively far.

Diacodexis was widespread, with fossils having been found in Pakistan, Europe, and North America.