Gomphos elkema (Gervais 1877) Paleocene ~55 mya was described as the earliest and most complete ancestor to modern rabbits. Derived from a sister to Plesiadapis, Gomphos phylogenetic preceded Oryctolagus, a living rabbit genus.
Distinct from Plesiadapis, the skull of Gomphos had a slightly downturned forehead and rostrum. Incisors 1 and 2 worked together against the lower two incisors. The jugal was more robust. A unique small process topped the orbit. The orbit was larger. The angular process of the mandible was large and descended with a large hook.
The forelimb and scapula were more gracile. The metacarpals were longer. The unguals were larger.
The ilium was longer. The femur was shorter and the tibia was both larger and longer. The foot was larger and longer with an elongated calcaneal heel.