Onychodectes, [193];

O. tissonensis, [193]

Onychogale, [134]

Onychomys, [479]

Opolemur, [544]

Opossum, [155];

Thick-tailed, [156];

Virginian, [155]

Orang Utan, [580], [581], [582], [583], [587], [589]

Orca, [375];