Arimasia germsi is an extinct sponge from the late Ediacaran, with possible affinities to the Archaeocyatha.

Estimated to be about 543 million years old, A. germsi has been identified as possibly being the oldest known archaeocyathan to date.

[1] The generic name Arimasia is derived from Arimas farm, the type locality of the fossil material.

The specific name germsi is derived from the surname of Gerard J.B. Germs, celebrating the 50th anniversary of his Ph.D. dissertation on The stratigraphy and paleontology of the lower Nama Group, South West Africa.

It features a sealed rounded base, with a circular opening at the top, which extends into the cone.