Hymenocarina

Canadaspis ("Shield of Canada") is an extinct genus of bivalved Cambrian marine arthropod, known from North America and China. They are thought to have been benthic feeders that moved mainly by walking and possibly used its biramous appendages to stir mud in search of food. They have been placed within the Hymenocarina, which includes other bivalved Cambrian arthropods.

Waptia is an extinct genus of marine arthropod from the Middle Cambrian of North America. It grew to a length of , and had a large bivalved carapace and a segmented body terminating into a pair of tail flaps. It was an active swimmer and likely a predator of soft-bodied prey. It is also one of the oldest animals with direct evidence of brood care. Waptia fieldensis is the only species classified under the genus Waptia, and is known from the Burgess Shale Lagerstätte of British Columbia, Canada. Specimens of Waptia are also known from the Spence Shale of Utah, United States.

Odaraia is an extinct genus of bivalved hymenocarine arthropod with a single known species Odaraia alata, found in the Middle Cambrian Burgess Shale in British Columbia, Canada.

Tuzoia (from Mount Tuzo, a mountain in the Canadian Rockies) is an extinct genus of large bivalved arthropod known from Early to Middle Cambrian marine environments from what is now North America, Australia, China, Europe and Siberia. The large, domed carapace reached lengths of , making them amongst the largest known Cambrian arthropods.

Perspicaris (from the Latin perspicax, meaning “sharp-sighted,” and caris, “crab/shrimp”) an extinct genus of bivalved arthropod from the Cambrian period. Fossils have been found in North America, primarily the Burgess Shale of British Columbia, Canada but also possibly the Wheeler Shale, Marjum Formation, Pioche Shale and Bloomington Formation. Two named species are known from the Burgess Shale Perspicaris dictynna and Perspicaris recondita, which differ in maximum size ( in P. recondita vs in P. dictynna), as well as proportions of the tail. Both species have a pair of stalked eyes, as well

Hymenocarina is an order of extinct marine arthropods known from the Cambrian. They possess bivalved carapaces, typically with exposed posteriors. Members of the group are morphologically diverse and had a variety of ecologies, including as filter feeders and as predators. Recent research has generally considered them to be stem or crown group members of Mandibulata, due to the presence of mandibles in well-preserved species.

Balhuticaris is a genus of extinct bivalved (referring to the carapace) hymenocarine arthropod that lived in the Cambrian aged Burgess Shale in what is now British Columbia around 506 million years ago. This extremely multisegmented (with over 100 segments) arthropod is the largest member of the group, and it was even one of the largest animals of the Cambrian, with individuals reaching lengths of 245 mm (9 in). Fossils of this animal suggests that gigantism occurred in more groups of Arthropoda than had been previously thought. It also presents the possibility that bivalved arthropo

Tokummia is a genus of fossil hymenocarine arthropod, known only by one species, '''Tokummia katalepsis''', from the middle Cambrian (508 million years old) Burgess Shale as found in a quarry in Marble Canyon in Canada.

Branchiocaris is an extinct genus of Cambrian bivalved arthropod. The type and best known species, Branchiocaris pretiosa, was described from the Burgess Shale of British Columbia, Canada, in 1929, originally placed in Protocaris, and was placed into its own distinct genus by Briggs in 1976. Several other possible species have been described from Cambrian deposits in China, and it is also possibly known from Cambrian deposits in Utah.

Jugatacaris is an extinct genus of bivalved arthropod known from a single species, Jugatacaris agilis found in the Cambrian Stage 3 aged Chengjiang biota of Yunnan, China. The carapace is around in length, with a pronounced ridge at the top of the carapace separating the two valves, which formed a fin-like structure raised above the carapace. The head has a pair of stalked eyes, as well as a dumbbell shaped medial eye between them. The head also bore a pair of mandibles as well as at least one and possibly two pairs of antennae. The trunk had up to 65 segments, each with biramous (two-branched

thumb|left|Life restoration Fibulacaris is a monotypic genus of fossil arthropod known only by one species, Fibulacaris nereidis, discovered from the Cambrian Burgess Shale of Canada. It was characterized by a bivalved carapace with an inverted rostrum, sandwiching the slender body with stalked eyes and homonomous appendages. It was probably an actively swimming filter feeder and possibly swam upside-down like some branchiopod crustaceans and horseshoe crabs. Phylogenetic analysis suggest it was a relative or member of Hymenocarina, which contains other bivalved arthropods.