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.
Hallucigenia is a genus of lobopodian, known from Cambrian aged fossils in Burgess Shale-type deposits in Canada and China, and from isolated spines around the world. The generic name reflects the type species' unusual appearance and eccentric history of study; when it was erected as a genus, H. sparsa was reconstructed as an enigmatic animal upside down and back to front. Lobopodians are a grade of Paleozoic panarthropods from which the velvet worms, water bears, and arthropods arose.
The Maotianshan Shales (帽天山页岩) are a series of Early Cambrian sedimentary deposits in the Chiungchussu Formation, famous for their Konservat Lagerstätten, deposits known for the exceptional preservation of fossilized organisms or traces. The Maotianshan Shales form one of some forty Cambrian fossil locations worldwide exhibiting exquisite preservation of rarely preserved, non-mineralized soft tissue, comparable to the fossils of the Burgess Shale of British Columbia, Canada. They take their name from Maotianshan Hill in Chengjiang County, Yunnan Province, China.
Aysheaia is an extinct genus of soft-bodied lobopodian, known from the Middle Cambrian Burgess Shale of British Columbia, Canada
Nectocaris is a genus of squid-like animal of controversial affinities known from the Cambrian period. The initial fossils were described from the Burgess Shale of Canada. Other similar remains possibly referrable to the genus are known from the Emu Bay Shale of Australia and Chengjiang Biota of China.
Sidneyia is an extinct arthropod known from fossils found from the Early to the Mid Cambrian of China and the Mid Cambrian Burgess Shale of British Columbia, Canada.
The Emu Bay Shale is a geological formation in Emu Bay, South Australia, containing a major Konservat-Lagerstätte. It is one of two in the world containing Redlichiidan trilobites. The Emu Bay Shale is dated as Cambrian Series 2, Stage 4, correlated with the upper Botomian Stage of the Lower Cambrian.
Cheloniellida is a taxon of extinct Paleozoic arthropods. As of 2018, 7 monotypic genera of cheloniellids had been formally described, whose fossils are found in marine strata ranging from Ordovician to Devonian in age. Cheloniellida has a controversial phylogenetic position, with previous studies associated it as either a member or relative of various fossil and extant arthropod taxa. It was later accepted as a member of Vicissicaudata within Artiopoda.
The Kaili Formation(凯里組) is a stratigraphic formation which was deposited during the Lower and Middle Cambrian. The formation is approximately 200 metres (660 ft) thick and was named after the city Kaili in the Guizhou province of southwest China.
Pambdelurion is an extinct genus of panarthropod from the Cambrian aged Sirius Passet site in northern Greenland. Like the morphologically similar Kerygmachela from the same locality, Pambdelurion is thought to be closely related to arthropods, combining characteristics of "lobopodians" with those of primitive arthropods.
Parapeytoia is a genus of extinct arthropod that lived over 530 million years ago in the Maotianshan shales of prehistoric China. It was interpreted as an anomalocaridid (radiodont) with legs, but later studies reveal it was a megacheiran, a group of arthropods which are no longer thought to be closely related to the radiodonts.
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.
Megacheira is an extinct class of predatory arthropods defined by their possession of spined "great appendages". Their taxonomic position is controversial, with studies either considering them stem-group euarthropods, or stem-group chelicerates. The homology of the great appendages to the cephalic appendages of other arthropods is also controversial. Uncontested members of the group were present in marine environments worldwide from the lower to middle Cambrian.
Pectocaris is an extinct genus of bivalved arthropods from the Cambrian Maotianshan Shales, Yunnan Province of China. There are currently three known species within the genus.
Marrellomorpha are an extinct group of arthropods known from the Cambrian to the Early Devonian. They lacked mineralised hard parts, so are only known from areas of exceptional preservation, limiting their fossil distribution. The best known member is Marrella, with thousands of specimens found in the Cambrian aged Burgess Shale of Canada. The group is divided up into two major orders, Marrellida and Acercostraca. Marrellida is recognised by the possession of head shields with two or three pairs of elongate spine-like projections, and three pairs of uniramous appendages on the cephalon, while Acercostraca generally have large ovoid carapaces that cover the entire upper half of the body, and five pairs of uniramous cephalic appendages. Both groups have unbranched antennules and a segmented trunk with biramous appendages. Recent research has suggested the previously enigmatic Cambrian trilobite-like arthropods Skania and Primicaris belong to this group. Their phylogenetic position is uncertain, various studies have alternatively placed them in the Arachnomorpha as relatives of Artiopoda, as related to Mandibulata, or as stem group euarthropods.
Omnidens amplus, meaning "large all-tooth", is an extinct species of large Cambrian animal known only from a series of large mouth apparatus, originally mistaken as the mouthparts of anomalocaridids. When first named, it was interpreted as a giant priapulid, but is now considered a panarthropod. Its mouth apparatus closely resembles that of the smaller gilled lobopodian Pambdelurion, indicating it is likely to have been a close relative of that species, with which it may be synonymous. With a maximum estimated body length of 1.5 metres (4.9 ft), Omnidens is suggested to have been the largest known free-living Cambrian organism. Omnidens fossils are found in the Maotianshan Shales.
Thelxiope is a genus of Cambrian and Ordovician arthropod. Four named species are known, the type species T. palaeothalassia is known from the Burgess Shale, Canada T. holmani is from the Wheeler Shale of Utah, Thelxiope tangi from the Linyi Lagerstätte of Shandong, China, and T. spinosa, which is known from both the Linyi Lagerstätte and the Wheeler Shale. An indeterminate species is also known from the Ordovician (Floian) Fezouata Formation in Morocco. It is a member of Mollisoniida, alongside close relatives Mollisonia, Corcorania and Urokodia. They are suggested to be stem-chelicerates.
The Artiopoda is a grouping of extinct arthropods that includes trilobites and their close relatives. It was erected by Hou and Bergström in 1997 to encompass a wide diversity of arthropods that would traditionally have been assigned to the Trilobitomorpha. Trilobites, in part due to their mineralising exoskeletons, are by far the most diverse and long lived members of the clade, with most records of other members, which lack mineralised exoskeletons, being from Cambrian deposits.
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.
Hallucigeniidae is a family of extinct worms belonging to the group Lobopodia that originated during the Cambrian explosion. It is based on the species Hallucigenia sparsa, the fossil of which was discovered by Charles Doolittle Walcott in 1911 from the Burgess Shale of British Columbia. The name Hallucigenia was created by Simon Conway Morris in 1977, from which the family was erected after discoveries of other hallucigeniid worms from other parts of the world. Classification of these lobopods and their relatives are still controversial, and the family consists of at least four genera.
