Naraoiidae is a family, of extinct, soft-shelled trilobite-like arthropods, that belongs to the order Nektaspida. Species included in the Naraoiidae are known from the second half of the Lower Cambrian to the end of the Upper Silurian. The total number of collection sites is limited and distributed over a vast period of time: Maotianshan Shale and Balang Formation (China), Burgess Shale and Bertie Formation (Canada), the Šárka Formation, Emu Bay Shale (Australia), Idaho and Utah (USA). This is probably due to the rare occurrence of the right circumstances for soft tissue preservation, needed for these non-calcified exoskeletons.
Sidneyia is an extinct marine arthropod known from fossils found from the Early to the Mid Cambrian of China and the Mid Cambrian Burgess Shale of British Columbia, Canada.
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.
Misszhouia is a genus of small to average sized marine trilobite-like arthropods within the Naraoiidae family, that lived during the early Cambrian period. The species are M. longicaudata, from the Maotianshan Shales, described in 1985, and M. canadensis, from the Burgess Shale and described in 2018, although later species may belongs to genus Naraoia instead.
A number of assemblages bear fossil assemblages similar in character to that of the Burgess Shale. While many are also preserved in a similar fashion to the Burgess Shale, the term "Burgess Shale-type fauna" covers assemblages based on taxonomic criteria only.
Haikoucaris is a genus of megacheiran arthropod that contains the single species Haikoucaris ercaiensis. It was discovered in the Cambrian Chengjiang biota of China.
Isoxys is a genus of extinct bivalved Cambrian arthropod; the various species of which are thought to have been freely swimming predators. It had a pair of large spherical eyes, and two large frontal appendages used to grasp prey.
Parapaleomerus is a genus of strabopid of small size found in Chengjiang biota, China. It contains one species, P. sinensis. Unlike the other members of Strabopida, Parapaleomerus lacks dorsal eyes and only possesses ten trunk tergites. The telson has been described as trapezoidal. All the trunk tergites are straight and increasingly curve backwards abaxially from T4–10. Specimens of Parapaleomerus sinesis are typically dorsoventrally compressed. The exoskeleton of P. sinensis has a semi-elliptical head shield that lacks any indication of the presence of dorsal eyes. The largest specimen described is recorded as 9.2 cm long, with a maximum width of 9 cm.
Primicaris is genus of Cambrian arthropod from the Chengjiang biota of China and the Burgess Shale of Canada. It contains a single described species, P. larvaformis.
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.
Eoredlichia is an extinct genus of trilobite of average to large size. It lived during the early Cambrian in the Chengjiang fauna of Yunnan, China, and in Australia and Thailand. Eoredlichia is compounded of the Greek ἠώς and Redlichia, a later but related genus, so it means "early Redlichia". The species epithet intermedia means intermediate, indicating it is morphologically intermediate between other species. Eofallotaspis gives rise to Lemdadella, and thence to Eoredlichia and the other Redlichiidae.
Kiisortoqia soperi is an extinct species of arthropod from the Early Cambrian Sirius Passet Lagerstätte in Greenland. While it had a superficially trilobite-like bodyform, it also possessed large frontal appendages similar to those of radiodonts.
Squamacula is an extinct artiopodan arthropod from the Cambrian Series 2. The type species S. clypeata was described in 1997 from the Chengjiang biota of Yunnan, China. At the time of description there were only two known specimens of S. clypeata, but now there are at least six known specimens. In 2012 a second species S. buckorum was described from the Emu Bay Shale of Australia.
Luohuilinella is an extinct genus of xandarellid artiopodan arthropod known from the Chengjiang biota of China. The type species Luohuilinella rarus was described in 2012. A second species Luohuilinella deletres was described in 2018. Both taxa are rare components of the assemblage. Like other Xandarellids and most artiopodans, it possessed an unmineralised exoskeleton. The type and currently only known specimen of L. rarus is known from a dorsal exoskeleton, around 17 mm long and 9 mm wide which consists of 27 tergites with pronounced pleural spines. L. deletres is much larger, with specimens being over 10 cm long, L. deletres possessed at least 11 pairs of biramous appendages. Both taxa are dorsoventrally flattened, making a benthic or nektobenthic lifestyle probable. Both taxa have pronounced notches in the cephalon to accommodate the stalked eyes.
Retifacies abnormalis is an extinct arthropod that lived in the lower Cambrian. 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.
Cheloniellon is a monotypic genus of cheloniellid arthropod, known only by one species, Cheloniellon calmani, discovered from the Lower Devonian Hunsrück Slate of Germany.
Kylinxia is a genus of extinct arthropod described in 2020. It was described from six specimens discovered in Yu'anshan Formation in southern China. The specimens are assigned to one species Kylinxia zhangi. Dated to 518 million years, the fossils falls under the Cambrian period. Announcing the discovery on 4 November 2020 at a press conference, Zeng Han of the Nanjing Institute of Geology and Paleontology, said that the animal "bridges the evolutionary gap from Anomalocaris to true arthropods and forms a key ‘missing link’ in the origin of arthropods," which was "predicted by Darwin’s evolutionary theory." The same day the formal description was published in Nature.
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.
Fengzhengia is an extinct genus of arthropod known from a single species, Fengzhengia mamingae from the Cambrian aged Chengjiang Biota of Yunnan, China. It is thought to be a basal arthropod, as one of the most basal members of Deuteropoda. Like other basal deuteropods, Fengzhengia has an upward curling pair of "frontal appendages" with at least 6 segments which bear endites, contrasting with the downward curving pair of frontal appendages possessed by radiodonts. The head has a pair of stalked eyes. The trunk had 15 tergites the first nine of which had upward facing spines, with the trunk terminating with a tail fan. The trunk seemingly had pairs of biramous limbs, with paddle-shaped exopods. It is thought to have been nektobenthic, and either a scavenger or a predator. A close relationship with the genus Kylinxia has been suggested.
Sklerolibyon is an extinct genus of megacheiran arthropod, known from the Cambrian aged Chengjiang biota of Yunnan, China. It is a member of the family Jianfengiidae, alongside Jianfengia and Fortiforceps, and possibly also Parapeytoia. Specimens are around 2.5 centimetres (0.98 in) in length. The body is greatly elongated, and head shield is heavily sclerotised, with a pair of spines radiating outward from the sides. Alongside the pair of great appendages, there are a pair of stalked eyes and at least two other pairs of limbs on the cephalon. The trunk has 34 segments with corresponding biramous appendages, with typically megacheiran paddle-shaped exopods. The tail is unknown but like Jianfengia probably ended in a telson spine.
