[3][4] Fossils of Plumulites were mostly known from isolated sclerites, and originally considered as arthropod or an echinoderm.

However, complete sclerite assemblages of P. richorum described in 1979 has shown that this animal is more likely to be annelid worm, the group which includes modern-day earthworm, leech and bristleworm.

[5] According to complete specimens, this animal is surrounded by pairs of outer and interior shell plates.

[6] Specimen of P. bengtsoni shows soft tissue including parapodia and chaetae.

[2] Preservation of jaw element of P. bengtsoni leads conclusion that machaeridians should be placed within the crown group of Phyllodocida.