Sipunculus (Sipunculus) longipapillosus Murina, 1968  

Elongate papillae in the middle of the trunk distinguish this species from other congeners, but it can be confused with Xenosiphon branchiatus, which has similar elongate papillae in the same trunk region. However, the elongate papillae in S. longipapillosus are arranged in longitudinal rows, whereas those in X. branchiatus are diagonal.