It is known from only a single species, P. atavus, found in the Cambrian Stage 3 aged Chengjiang Biota of Yunnan, China.
The head bore a pair of small frontal appendages and ventrally directed circular mouth.
[1] In the original description, The trunk appendages were interpreted as swimming flaps, which suggest a nektonic life style and close relationship with stem-group arthropods such as the "gilled lobopodians" Kerygmachela and Pambdelurion, opabiniids and radiodonts.
[1] However, recent research suggests it may instead be a larval siberiid, a group of benthic lobopodian nest within arthropod stem-group, and the trunk appendages were re-interpreted as stout lobopods.
Since it may represent the larva of any described siberiids from the same strata (e.g. Megadictyon, Jianshanopodia) and cannot be accurately identified, Parvibellus is considered to be a nomen dubium.