Monotypic artiopod genera

Helmetia is an extinct genus of arthropods from the middle Cambrian (Wuliuan). Fossils of the type species Helmetia expansa have been found in the Burgess Shale of Canada. It is characterized by a pair of spines in front of its head. It is classified under Conciliterga, a group of trilobitomorph artiopod.

Retifacies abnormalis is an extinct arthropod that lived in the lower Cambrian (about 518 million years ago). Its fossil remains have been found in the Maotianshan Shales of Yunnan, China. It is a member of the Artiopoda, and closely related to Pygmaclypeatus.

Kodymirus is an extinct genus of Early Cambrian arthropod, known from the Czech Republic. Although it possessed great appendage-like raptorial arms, it was not homologous with those of megacheirans. Kodymirus is currently considered a member of Vicissicaudata, closely related to aglaspidids, and more distantly to trilobites. It is part of a small and low-diversity Paseky Shale fauna group, which dwelt in brackish waters.

Cheloniellon is a monotypic genus of cheloniellid arthropod, known only by one species, Cheloniellon calmani, discovered from the Lower Devonian Hunsrück Slate of Germany.