Canadaspis 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 6.65 cm (3 in), 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.
Perspicaris 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, as well as proportions of the tail. Both species have a pair of stalked eyes, as well as a pair of large segmented antennae. The tail is forked and spiny. They are thought to have been active swimmers (nektonic).
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.
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. Branchiocaris pretiosa is around 80–90 millimetres (3.1–3.5 in) in length, with a highly segmented trunk, consisting of at least 44 ring-like segments, terminating in a forked tail telson. At the front of the animal is a pair of short segmented tapered antennules with at least 20 segments, as well as a pair of claw appendages. It was likely an active swimmer, and used the claw appendages to bring food to the mouth.
Tuzoia 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 180 millimetres (7.1 in), making them amongst the largest known Cambrian arthropods.
Clypecaris is genus of bivalved Cambrian arthropod known from the Chengjiang biota of Yunnan, China. The genus was initially described for the type species C. pteroidea by Hou, 1999. A second species C. serrata was described by Yang et al. in 2016. The species are primarily distinguished by the presence of a serrated edge on the front of the carapace of C. serrata. C. serrata is noted for the modification of an anterior pair of limbs into spined grasping appendages, indicating a predatory lifestyle. It is unknown whether a similar structure was present in C. pteroidea.Clypecaris is considered to likely be a member or a close relative of Hymenocarina, and is closely related to Perspicaris. As well as to Ercaicunia.
Ercaicunia is genus of bivalved Cambrian arthropod from the Chengjiang biota of Yunnan, China. It contains a single species, E. multinodosa that was described by Luo et al. in 1999. The total length of the body ranges from 8 to 11 millimetres. The bivalved carapace covered about a third of the total body-length, and has up to six serrations on its forward edge. The head has a pair of large uniramous antennae, as well as a smaller pair of secondary antennae, as well as pair of mandibles and maxillae. The trunk has 16 pairs of biramous appendages. Specimens were CT scanned in 2019, which suggested it to be a stem-group crustacean. Other subsequent studies have recovered it as a member of Hymenocarina, which contains other bivalved Cambrian arthropods.
Haikoucaris is a genus of megacheiran arthropod that contains the single species Haikoucaris ercaiensis. It was discovered in the Cambrian Chengjiang biota of China.
Pectocaris is an extinct genus of bivalved arthropods from the Cambrian Maotianshan Shales, Yunnan Province of China. There are currently four known species within the genus.
Radiodonta is an extinct order of stem-group arthropods that was successful worldwide during the Cambrian period. Radiodonts are distinguished by their distinctive frontal appendages, which are morphologically diverse and were used for a variety of functions. Radiodonts were among the earliest large predators, but they also included sediment sifters and filter feeders. Some of the most famous species of radiodonts are the Cambrian taxa Anomalocaris canadensis, Hurdia victoria, Peytoia nathorsti, Titanokorys gainesi, Cambroraster falcatus and Amplectobelua symbrachiata. The later surviving members include the subfamily Aegirocassisinae from the Early Ordovician of Morocco and the Early Devonian member Schinderhannes bartelsi from Germany.
Marble Canyon surrounds Tokumm Creek just above its confluence with the Vermilion River, at the north end of Kootenay National Park in the Canadian Rockies of British Columbia. South of the canyon on Highway 93 is Numa Falls on the Vermilion River.
Tokummia is a genus of fossil hymenocarine arthropod, known only by one species, Tokummiakatalepsis, from the middle Cambrian Burgess Shale as found in a quarry in Marble Canyon in Canada.
Hymenocarina is an order of extinct 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.
Titanokorys is a genus of extinct hurdiid (peytoiid) radiodont that existed during the mid Cambrian. It is the largest member of its family from the Cambrian, with a body length of 50 cm (20 in) long, making it one of the largest animals of the time. It bears a resemblance to the related genus Cambroraster. Fossils of T. gainesi were first found within the Marble Canyon locality within the Burgess Shale in 2018. The fossils were not named until 2021 because they were assumed to be giant specimens of Cambroraster.
Erratus is an extinct genus of marine arthropod from the Cambrian of China. Its type and only species is Erratus sperare. Erratus is likely one of the most basal known arthropods, and its discovery has helped scientists understand the early evolution of arthropod trunk appendages. Some of the stem-arthropods like radiodonts did not have legs, instead they had flap like appendages that helped them swim. Erratus on the other hand had not only flaps but also a set of primitive legs. It also supported the theory that the gills of aquatic arthropods probably evolved into the wings and lungs of terrestrial arthropods later in the Paleozoic.
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.
Nereocaris is an extinct genus of bivalved hymenocarine arthropod that lived in the Cambrian aged Burgess Shale in what is now British Columbia around 506 million years ago. Two species are known.
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 28 to 37 millimetres 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 antennules. The trunk had up to 65 segments, each with biramous appendages. The appendages had thin endopods with 30 podomeres, each bearing a spiny endite, with the endopods ending with a terminal claw. The appendages also had overlapping flap-like exopods, which are elongated, being at maximum eight times as long as they are wide, which on their posterior edge are covered with setae. The trunk ended with a forked tail. It was likely an actively swimming filter feeder, using its constantly beating appendages to sift food from the water column, which was then passed forward along the U-shaped food groove between the appendage pairs towards the mouth. While initially placed as a crustaceanomorph, later studies considered to be a member of Hymenocarina, which contains numerous other similar bivalved Cambrian arthropods.
Isoxyids are members of the order Isoxyida and the family Isoxyidae, a group of basal arthropods that existed during the Cambrian period. It contains two genera, Isoxys, with 20 species found worldwide, and Surusicaris known from a single species found in the Burgess Shale of Canada. They are distinguished by their bivalved carapaces and pair of upward curving grasping frontal appendages.
