Amplinus bituberculosus is a species of millipede in the family Aphelidesmidae that is endemic to San Vito, Costa Rica, where it was found on 17–18 April 1972.
The head have a deep median sulcus, which is sharply impressed and is extended between antennae and almost next to the posterior edge of the vertex.
The metazonites ventral surface is conic and tuberculate at the same time, and is located next to the keels, or rather to the posterior base which is next to it.
The last segments sides are parallel and end up with a rounded and acute apex.
The opening of the gonopod have a posterior with raised rim that ends into an angular and sometimes rounded shoulder.