Cambrian genus extinctions

Helmetia is an extinct genus of arthropods from the middle Cambrian (Wuliuan). Fossils of the type species Helmetia expansa have been found in the Burgess Shale of Canada. It is characterized by a pair of spines in front of its head. It is classified under Conciliterga, a group of trilobitomorph artiopod.

Choia is a genus of extinct demosponge ranging from the Cambrian until the Lower Ordovician periods. Fossils of Choia have been found in the Burgess Shale in British Columbia; the Maotianshan shales of China; the Wheeler Shale in Utah; the Itajaí Basin in Brazil; and the Lower Ordovician Fezouata formation. It was first described in 1920 by Charles Doolittle Walcott.

Orthrozanclus (from Greek + ( + ), "dawn scythe") is a genus of sea creatures known from two species, O. reburrus from the Middle Cambrian (~) Burgess Shale and O. elongata from Early Cambrian (~) Maotianshan Shales. Animals in this genus were one to two centimeters long, with spikes protruding from their armored bodies. The placement of this genus into a specific family is not universally accepted.

Stromatoveris psygmoglena is a genus of fossil organism from the Chengjiang deposits of Yunnan that was originally aligned with the fossil Charnia (strictly, the Charniomorpha) from the Ediacara biota. However, such an affinity was thought to be developmentally implausible and so S. psygmoglena was thought to be either a sessile basal ctenophore, or a sessile organism closely related to ctenophores instead. Nevertheless, a 2018 phylogenetic analysis by Jennifer Hoyal Cuthill and Jian Han indicated that Stromatoveris was a member of Animalia and closely related to ediacaran frond-like lifeforms

Hymenocaris is a genus of Cambrian marine arthropod. The type species, Hymenocaris vermicaudata is known from the Upper Cambrian (Furongian) Ffestiniog Formation, in North Wales, United Kingdom.

Misszhouia is a genus of small to average sized (up to long) 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.

Ellipsocephalus Zenker, 1833, is a genus of blind Cambrian trilobite, comprising benthic species inhabiting deep, poorly lit or aphotic habitats. E. hoffi is a common trilobite mainly from central Europe (Czech Republic).

Emuella is a genus of Cambrian trilobites of the family Emuellidae. Its fossils have been found in South Australia.

Takakkawia is a genus of sponge in the order Protomonaxonida and the family Takakkawiidae. It is known from the Middle Cambrian Burgess Shale that reached around 4 cm in height. Its structure comprises four columns of multi-rayed, organic spicules (perhaps originally calcareous or siliceous) that align to form flanges. The spicules form blade-like structures, ornamented with concentric rings.

Jianshanopodia is a monotypic genus of Cambrian lobopodian, discovered in the Maotianshan Shales of Yunnan, China.

Cucumericrus ("cucumber-leg") is an extinct genus of stem-arthropod. The type and only species is Cucumericrus decoratus, with fossils discovered from the Maotianshan Shales of Yunnan, China.

Louisella is a genus of worm known from the Middle Cambrian Burgess Shale. It was originally described by Charles Walcott in 1911 as a holothurian echinoderm, and represents a senior synonym of Miskoia, which was originally described as an annelid. 48 specimens of Louisella are known from the Greater Phyllopod bed, where they comprise < 0.1% of the community. It has been stated to have palaeoscolecid-like sclerites, though this is not in fact the case.

Eoredlichia is an extinct genus of trilobite of average to large size (up to long, or when including the spine on the ninth thorax segment pointing horizontally to the back, that itself equals the main body length). It lived during the early Cambrian (late Atdabanian) in the Chengjiang fauna of Yunnan, China, and in Australia and Thailand. Eoredlichia is compounded of the Greek (eos, dawn) 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

Retifacies abnormalis is an extinct arthropod that lived in the lower Cambrian (about 518 million years ago). 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.

Balcoracania dailyi is a small (typically about ) trilobite of the family Emuellidae. Its fossils have been found in south Australia and Antarctica.

Echmatocrinus brachiatus is an extinct species of Cambrian animal which resembles a crinoid or an octocoral. Its exact taxonomy is still a subject of debate. It is known only from the Burgess Shale. Around 20 specimens of Echmatocrinus are known; these comprise <0.02% of the community.

thumb|left|Kootenia assemblage at the Geological Museum in Copenhagen

Siberion is an extinct genus of lobopodian from the Sinsk biota of Russia. Its anatomy, including the proboscis-like organ projecting from the face and prominent grasping first pair of appendages, suggests that xenusians like this organism may have been phylogenetically related to anomalocaridids, like Anomalocaris. Only two incomplete specimens are known, and the probability of finding more is low, as the Sinsk Algal Lens has been nearly destroyed by commercial fossil collectors.

Anabarites is a problematic lower Cambrian genus, and is one of the small shelly fossils. It was abundant in the early Tommotian and is also found in the Nemakit-Daldynian. The fossils represent the triradially symmetrical mineralised tube in which the organism dwelt; it was sedentary. It is named after the Anabar region in Yakutia, Russia; its name does not imply 'heavy'.

Asaphiscus is a genus of trilobite that lived in the Cambrian. Its remains have been found in Australia and North America, especially in Utah.

left|thumb|Life restoration

left|thumb|Life restoration Paucipodia inermis is a lobopod known from the Lower Cambrian Chengjiang lagerstätte.

Skania is a Cambrian fossil arthropod. The type species, S. fragillis, is known from the Burgess Shale of British Columbia, Canada. A second possible species "S." sundbergi is known from the Kaili Formation of China, but its placement within the genus has been questioned.

Omnidens, meaning "all-tooth", is an extinct genus of large Cambrian animal known only from a series of large mouth apparatus and sclerotized talon-like structures, 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 a maximum estimated body length of , Omnidens is suggested to have been the largest known free-living Cambrian org

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&nbsp;mm (9&nbsp;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

Herpetogaster is an extinct cambroernid genus of animal from the Early Cambrian Chengjiang biota of China, Balang Formation of China, Pioche Formation of Nevada and Middle Cambrian Burgess Shale of Canada containing the species Herpetogaster collinsi and Herpetogaster haiyanensis.

Yawunik is an extinct genus of Cambrian megacheiran ("Great appendage" arthropod) known from the Burgess Shale in Canada ( Marble Canyon locality). The type species has been named Yawunik kootenayi after the Kootenay, both a geographic area (and National Park, where the fossil was found) and North American First Nation, also known as the Ktunaxa. The genus name is derived from , the name of a primordial sea monster in Ktunaxa mythology. The fossil dates back to 508 million years ago.

Molaria is a genus of Cambrian arthropod, the type species M. spinifera is known from the Middle Cambrian Burgess Shale. 144 specimens of Molaria are known from the Greater Phyllopod bed, where they comprise 0.27% of the community. A second species M. steini was described from the Sirius Passet in Greenland in 2017.

Yunnanocephalus is a genus of ptychopariid trilobite. It lived during the late Atdabanian and Botomian stages, in what are currently Antarctica, Australia and China. It was a "moderately common" member of the Chengjiang Fauna.

Emeraldella is a genus of arthropod known from the Middle Cambrian of North America. The type species E. brocki was described in 1912 from the Burgess Shale. 21 specimens of Emeraldella are known from the Greater Phyllopod bed, where they comprise < 0.1% of the community. A re-study on the species was done in 2012. A second species E. brutoni is known from the Wheeler Shale, which was described in 2011. An additional specimen of E. brutoni was described in 2019, which revealed more of the anatomy. It has been placed as a basal member of the clade Vicissicaudata within Artiopoda, a group of art

Zhongxiniscus is a genus of primitive chordate from eastern Yunnan that lived during the Early Cambrian. Known from a single specimen, it had a small, broad and short, fish-like body that was roughly ten millimeters in length. It possessed S-shaped myomeres, numbering roughly seven per one millimeter of length. Two triangular fins are evident on the dorsal margin.

Plectronoceras is the earliest known shelled cephalopod, dating to the Late Cambrian. None of the fossils are complete, and none show the apex or aperture of the shell. Approximately half of its shell was filled with septa; 7 were recorded in a shell. Its shell contains transverse septa separated by about half a millimetre, with a siphuncle on its concave side. Its morphology matches closely to that hypothesised for the last common ancestor of all cephalopods.

Kodymirus is an extinct genus of Early Cambrian arthropod, known from the Czech Republic. Although it possessed great appendage-like raptorial arms, it was not homologous with those of megacheirans. Kodymirus is currently considered a member of Vicissicaudata, closely related to aglaspidids, and more distantly to trilobites. It is part of a small and low-diversity Paseky Shale fauna group, which dwelt in brackish waters.

Xianguangia is a soft-bodied stem ctenophore assigned to Dinomischiidae from the Chengjiang Biota of China.

Acmarhachis is a genus of trilobites in the order Agnostida, which lived in what are now Australia (Queensland, Tasmania), Canada (British Columbia, Newfoundland, Northwest Territories), China (Anhui), Kazakhstan, Russia (Kharaulakh), and the US (Alaska, Alabama, Nevada, Maryland, Vermont). It was described by Resser in 1938, and the type species is Acmarhachis typicalis.

Pahvantia is an extinct genus of hurdiid radiodont from the Cambrian period. It is known by a single species, Pahvantia hastata, described from Wheeler Shale and Marjum Formation in Utah. Although it was once considered as a filter feeder based on the large number of putative setae on the frontal appendage, these structures were later interpreted as fossil material of the "trunk" section.

fossil genus of trilobites

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.

Hazelia is a genus of spicular Cambrian demosponge known from the Burgess Shale, the Marjum formation of Utah, and possibly Chengjiang. It was described by Charles Walcott in 1920.

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.

Abakania is an extinct genus of corynexochid trilobite in the family Corynexochidae. It lived during the Botomian stage, which lasted from approximately 524 to 518.5 million years ago. This faunal stage was part of the Cambrian Period.

Cricocosmia is an abundant palaeoscolecid worm endemic to the Early Cambrian Chengjiang Biota of Yunnan, China. It resembles modern priapulids, and holds a pivotal role in understanding the evolution of early ecdysozoans. It possessed paired lateral sclerites and paired ventral projections which have been compared with early panarthropod legs. It was a detritivore, living in shallow horizontal burrows, sometimes in great concentration.

Chengjiangocaris is an extinct genus of fuxianhuiid arthropod known from the Cambrian of South China. It contains two species, C. longiformis which was described in 1991. C. kunmingensis was described in 2013 by Javier Ortega-Hernández and colleagues. One specimen of C. kunmingensis shows detailed evidence of a nervous system. The nervous system of the chengjiangocaris is and has always been very complex to understand but a recent discovery of the ladder like ventral nerval cords and segmental ganglia of the related chengjiangocaris together with the brain provides the most comprehensive recon

Tommotia is a small shelly fossil from the Early Cambrian Period. Originally, only a cone-shaped shell was recognized, which was originally thought to be an early cephalopod, with either squid-like tentacles or a snail-like foot. More recent investigation has shown that the cone is not the remains of a complete animal, but a sclerite of a larger, soft-bodied animal that would have resembled a chiton or a sea mouse. The fossils called Camanella may be another type of sclerite from the same animal.

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.

Yochelcionella is an extinct genus of basal molluscs which lived during the Tommotian epoch, the first epoch of the Cambrian period. This genus is often reconstructed to resemble snails.