Diacodexis is a genus of very primitive ungulate that lived during the Eocene epoch of North America, Europe and Asia. It belonged to the Dichobunidae family and represented one of the earliest known ungulates. In life, Diacodexis would have resembled a duiker or chevrotain with a long tail. Each foot retained several toes with small hooves. They were probably fast-running animals due to their long limbs and slender build body. The shape of their teeth suggests they were browsers, feeding on small leaves in the undergrowth of dense forests or semi-open landscapes.
Diacodexis secans is one of many species within its genus. At least 14 species are currently known. Fossils of D. secans have been found in the USA of North America, dating from the Eocene epoch. The genus has been widely applied to many species of primitive ungulate and therefore contains several species that are in need revision. D. secans was about the size of a cat, reaching 50 cm in length (without the tail) and weighted about 3 kg.
E. D. Cope. 1881. On the Vertebrata of the Wind River Eocene beds of Wyoming. Bulletin of the United States Geological and Geographical Survey 6(1):183-202