Two specimens of Onychonycteris were found in the Green River Formation in 2003, and placed in a new family when the discovery was published in Nature, in February 2008.
Dua spesimen dari Onychonycteris ditemukan di Green River Formation tahun 2003, dan diletakkan dalam familia baru saat penemuannya dimuat di majalah Nature, bulan Februari 2008.