Otavia antiqua is an early sponge-like fossil found in Namibia in the Etosha National Park. It is claimed to be the oldest animal fossil, being found in rock aged between 760 and 550 million years ago. The genus was named after the Otavi group in which the fossils were found. The oldest fossils are prior to the Cryogenian glaciations, but the latest found were from the Nama group rocus which are from the Ediacaran period.
The shape of the fossils is irregular but rounded. The size varies from a third of a millimeter to 5 mm (0.20 in). They are hollow inside, and have many small holes connecting the interior to the outside. The material of the outer wall is predominantly calcium phosphate.