Hardieopterids are defined as kokomopteroids with lateral pleurae on their metastoma and pretelson, large lunate scales on the posterior margin of the carapace and a clavate telson. The opisthosoma shows both a second and fourth order differentiation into a mesosoma and metasoma. Appendages II-IV are unknown, though appendage V is spiniferous and VI is non-spiniferous as in the genus Hardieopterus.[2]
The Hardieopteridae display some adaptations towards sweep-feeding, such as a broadening of the metastoma and the spines of the anterior prosomal appendages and may even have been benthic bottomdwellers living partially buried in the substrate.[2]