Omomyids were small-bodied, tarsier-like primates that lived on the northern continents between 56 and 37 million years ago (Ma). They represent the earliest known definitive primates in the fossil record, appearing slightly earlier than members of the other large Eocene primate radiation, Adapiformes. Both of these groups, together with extant crown primates, constitute Euprimates and share typical features, such as the presence of nails instead of claws on most digits, an opposable hallux (big toe), and a postorbital bar. Additionally, most omomyids were orthograde, leaping forms with relatively large hands and elongate foot bones. They had globular braincases and large, front-facing orbits. Omomyids were most abundant and diverse in North America, less so in Europe, and rare but present in Asia during the Eocene. The appearance of omomyids at 56 Ma indicates that the split between the two great groups of living primates, Strepsirrhini and Haplorhini, occurred before this time.