Sphaeriodesmus filamentosus is a species of millipede in the family Sphaeriodesmidae that is endemic to San Vito, Costa Rica.
The antennal second, third, and fifth joints are almost equal in length, while the sixth one is the longest and the fourth is the shortest.
The first segment is almost trapezoidal shaped and is twice as wide and long as the rest.
The anterior margin is almost parallel while posterior one is straight and rounded.
The clypeus have anterior rows of 18-20 setae, each of which is different in length.