Cambrian genus extinctions

Pikaia gracilens is an extinct, primitive chordate marine animal known from the Middle Cambrian Burgess Shale of British Columbia. Described in 1911 by Charles Doolittle Walcott as an annelid, and in 1979 by Harry B. Whittington and Simon Conway Morris as a chordate, it became "the most famous early chordate fossil", or "famously known as the earliest described Cambrian chordate". It is estimated to have lived during the latter period of the Cambrian explosion. Since its initial discovery, more than a hundred specimens have been recovered.

Hallucigenia is a genus of lobopodian known from Cambrian-aged fossils in Burgess Shale-type deposits in Canada (Burgess Shale) 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.

Wiwaxia is a genus of prehistoric soft-bodied animals that were covered in carbonaceous scales and spines that protected it from predators. Wiwaxia fossils—mainly isolated scales, but sometimes complete, articulated fossils—are known from early Cambrian and middle Cambrian fossil deposits across the globe. The living animal would have measured up to when fully grown, although a range of juvenile specimens are known, the smallest being long.

Yunnanozoon lividum (from Yunnan, and Ancient Greek ζῷον (zôion), meaning "animal", with specific name coming from Latin lividum; (lead-coloured), referring to preserved colour of specimens) is an extinct species of bilaterian animal from the Lower Cambrian Chengjiang biota of Yunnan province, China. Its affinities have long been the subject of controversy.

Nectocaris is a genus of squid-like animal 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.

Aysheaia is an extinct genus of soft-bodied lobopodian, known from the Middle Cambrian Burgess Shale of British Columbia, Canada.

Ottoia is a stem-group archaeopriapulid worm known from Cambrian fossils. Although priapulid-like worms from various Cambrian deposits are often referred to Ottoia on spurious grounds, the only clear Ottoia macrofossils come from the Burgess Shale of British Columbia, which was deposited . Microfossils extend the record of Ottoia throughout the Western Canada Sedimentary Basin, from the mid- to late Cambrian. A few fossil finds are also known from China.

Marrella is an extinct genus of marrellomorph arthropod known from the Middle Cambrian of North America and Asia. It is the most common animal represented in the Burgess Shale of British Columbia, Canada, with tens of thousands of specimens collected. Much rarer remains are also known from deposits in China.

Hurdia is an extinct genus of hurdiid radiodont that lived 505 million years ago during the Cambrian Period. Fossils have been found in North America, China, and the Czech Republic.

Amplectobelua (meaning "embracing beast") is an extinct genus of late Early Cambrian amplectobeluid radiodont, a group of stem arthropods that mostly lived as free-swimming predators during the first half of the Paleozoic Era.

Kerygmachela kierkegaardi is a kerygmachelid gilled lobopodian from the Cambrian Stage 3 aged Sirius Passet Lagerstätte in northern Greenland. Its anatomy strongly suggests that it, along with its relative Pambdelurion whittingtoni, was a close relative of radiodont (Anomalocaris and relatives) and euarthropods. The generic name "Kerygmachela" derives from the Greek words Kerygma (proclamation) and Chela (claw), in reference to the flamboyant frontal appendages. The specific name, "kierkegaardi" honors Danish philosopher Søren Kierkegaard.

is an extinct genus of lobopodian worm characterized by its net-like sclerite armour plates, known from Cambrian deposits around the world. Soft-bodied fossils which preserve more than the sclerites are only known from the Chengjiang Lagerstätte of Yunnan, China.

Sanctacaris is a Middle Cambrian arthropod from the Burgess Shale of British Columbia. It was most famously regarded as a stem-group chelicerate, a group which includes horseshoe crabs, spiders and scorpions, although subsequent phylogenetic studies have not always supported this conclusion. Its chelicerate affinities regain support in later observations, alongside the reassignment of Habelia optata as a sanctacaridid-related basal chelicerate. It has been placed as a member of the extinct family Sanctacarididae alongside Wisangocaris and Utahcaris.

Naraoia is a genus of small-to-average-size (about long) marine arthropods within the family Naraoiidae, that lived from the early Cambrian to the late Silurian period. The species are characterized by a large alimentary system and sideways oriented antennas.

Alalcomenaeus is one of the most widespread and longest-surviving arthropod genera of the Early and Middle Cambrian. Known from over 300 specimens in the Burgess Shale and the Chengjiang biota. It is a member of the family Leanchoiliidae in the group Megacheira.

Amiskwia is a genus of soft-bodied marine animals known from fossils of the Middle Cambrian Lagerstätten both in the Burgess Shale in British Columbia, Canada and the Maotianshan shales of Yunnan Province, China. It is interpreted as a member of the clade Gnathifera sensu lato or as a basal cucullophoran.

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.

Leanchoilia is a megacheiran marine arthropod known from Cambrian deposits of the Burgess Shale in Canada and the Chengjiang biota of China.

Metaspriggina is a genus of chordate initially known from two specimens in the Middle Cambrian Burgess Shale and 44 specimens found in 2012 at the Marble Canyon bed in Kootenay National Park.

300px|left|thumb|Reconstruction of the head region of Cambroraster falcatus. A: Dorsal view, B: Ventral view, Ey: Eye, Fa: Frontal appendage, He:H-element, Bp: Bilobate posterior region, Lp: Posterolateral process, Oc: Oral cone, Pe: P-element, Pn: P-element neck Cambroraster is an extinct monotypic genus of hurdiid radiodont, dating to the middle Cambrian, and represented by the single formally described species Cambroraster falcatus. Hundreds of specimens were found in the Burgess Shale, and described in 2019. A large animal (for its era) at up to (but not as long as Titanokorys at ), it is

Fuxianhuia is a genus of Lower Cambrian fossil arthropod known from the Chengjiang fauna in China. Its purportedly primitive features have led to it playing a pivotal role in discussions about the euarthropod stem group. Nevertheless, despite being known from many specimens, disputes about its morphology, in particular its head appendages, have made it one of the most controversial of the Chengjiang taxa, and it has been discussed extensively in the context of the arthropod head problem.

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.

Dinomischus is an extinct genus of stalked filter-feeding animals within the Cambrian period, with specimens known from the Burgess Shale, the Maotianshan Shales, the Kaili Formation and the Marjum Formation. While long of uncertain affinities, recent studies have suggested it to be a stem-group ctenophore.

Redlichia is a genus of redlichiid trilobite in the family Redlichiidae, with large to very large species (up to long). Fossils of various species are found in Lower Cambrian (Toyonian)-aged marine strata from China, Korea, Pakistan, the Himalayas, Iran, Spain, southern Siberia, and Antarctica, and from Middle Cambrian (Ordian)-aged marine strata of Australia.

Utaurora is an extinct genus of opabiniid, which were stem-arthropods closely related to true arthropods and radiodonts; the type species is U. comosa. The animal's fossils come from the Cambrian of Utah. This genus is the only other known unquestionable opabiniid, with the other being Opabinia itself. There are other animals like Myoscolex and Mieridduryn that could be opabiniids, but the classification of those two genera is still debated.

Burgessochaeta is an extinct genus of polychaete annelids from the Middle Cambrian. Its fossils have been found in the Burgess Shale in British Columbia, Canada. The genus was described by Conway Morris (1979) and re-examined by Eibye-Jacobsen (2004).

Olenellus is an extinct genus of redlichiid trilobites, with species of average size (about long). It lived during the Botomian and Toyonian stages of the Lower Cambrian (Olenellus-zone), , in what is currently North America, part of the palaeocontinent Laurentia.

Titanokorys is a genus of extinct hurdiid (peytoiid) radiodont (a grouping of primitive stem arthropods which lived during the early Paleozoic) that lived during the Miaolingian epoch of the middle Cambrian. It is the largest member of its family from the Cambrian, with an estimated body length of around long, making it one of the largest animals of the time. It bears a resemblance to the related, and contemporary, genus Cambroraster. Fossils of T. gainesi were first found within the Marble Canyon locality of the Burgess Shale in 2018, however the fossils were not named until 2021 because they

Yohoia is an extinct genus of fossil megacheiran arthropod from the Cambrian period. The type species, Yohoia tenuis, has been found in the Burgess Shale formation of British Columbia. 711 specimens of Yohoia are known from the Greater Phyllopod bed, where they comprise 1.35% of the community. In 2015, Conway Morris et al. reported another species, Y. utahana, from the Marjum Formation, Utah.

Paradoxides is a genus of large to very large trilobite found throughout the world during the Middle Cambrian period. One record-breaking specimen of Paradoxides davidis, described by John William Salter in 1863, is . The cephalon was semicircular with free cheeks ending in long, narrow, recurved spines. Eyes were crescent shaped providing an almost 360° view, but only in the horizontal plane. Its elongate thorax was composed of 19–21 segments and adorned with longish, recurved pleural spines. Its pygidium was comparatively small. Paradoxides is a characteristic Middle-Cambrian trilobite of th

Xenusion auerswaldae is an early lobopodian known from three specimens found in glacial erratics on the Baltic coast of Germany. Another specimen, discovered shortly after the holotype, was briefly observed but soon went missing. Except for this lost specimen, the fossils probably originated in the Kalmarsund Sandstone of Southern Sweden, which was deposited in the Lower Cambrian (Upper Tommotian–Lower Atdabanian; Stages 2→3). It is the oldest currently known lobopodian with soft body fossils.

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.

Diania is an extinct genus of lobopodian panarthropod found in the Lower Cambrian Maotianshan shale of China, represented by a single species - D. cactiformis. Known during its investigation by the nickname "walking cactus", this organism belongs to a group known as the armoured lobopodians, and has a simple worm-like body with robust, spiny legs. Initially, the legs were thought to have a jointed exoskeleton and Diania was suggested to be evolutionarily close to early arthropods, but many later studies have rejected this interpretation.

Caryosyntrips ("nutcracker") is an extinct genus of stem-arthropod which known from Canada, United States and Spain during the middle Cambrian. It was first named by Allison C. Daley and Graham E. Budd in 2010, with the type species being Caryosyntrips serratus.

Conulariida are an extinct group of medusozoan cnidarians known from fossils spanning from the latest Ediacaran up until the Late Triassic. They are almost exclusively known from their hard external structures (alternatively referred to as a theca, periderm or test), which were pyramidal in shape and made up of numerous lamellae (thin layers). They are thought to have been sessile animals that grew with the narrower tip anchored to the seafloor, with the wider end bearing an array of tentacles used to ensnare prey.

Parapeytoia is a genus of Cambrian arthropod. The type and only described species is Parapeytoia yunnanensis, which lived over 518 million years ago (Cambrian Stage 3) in the Maotianshan shales of Yunnan, China. Unidentified fossils from the same genus have also been discovered from the nearby Wulongqing Formation (Cambrian Stage 4).

The halkieriids are a group of fossil organisms from the Lower to Middle Cambrian. Their eponymous genus is Halkieria .

Eldonia is an extinct soft-bodied cambroernid best known from the Fossil Ridge outcrops of the Burgess Shale, particularly in the 'Great Eldonia layer' in the Walcott Quarry. In addition to over 550 specimens collected by Walcott, 224 specimens of Eldonia are known from the Greater Phyllopod bed, where they comprise 0.43% of the community. Species also occur in the Chengjiang biota, and Siberia.

Odontogriphus (from , 'tooth' and , 'riddle') is a genus of soft-bodied animals known from middle Cambrian Lagerstätte. Reaching as much as in length, Odontogriphus is a flat, oval bilaterian which apparently had a single muscular foot and a "shell" on its back that was moderately rigid but of a material unsuited to fossilization.

Kylinxia is a genus of extinct arthropod described in 2020. It was described from six specimens discovered in Yu'anshan Formation (Maotianshan Shales) 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 "predicte

thumb|right|250px|Elrathia kingii growth series with holaspids ranging from 16.2 mm to 39.8 mm in length

Olenoides is a genus of trilobite from the Cambrian period. Its fossils can be found with soft body parts intact in the Burgess Shale in Canada. Fossils of this genus can also be found in the Wheeler Shale and Marjum Formation of Utah in the United States of America, among other localities. Species within this genus range in size, with most being medium-sized trilobites (Olenoides Serratus from the Burgess Shale can be up to 9 centimeters in length). Specimens of Olenoides Superbus, pictured on the right, an especially large species, can reach sizes of well over 10 centimeters in length. Oleno

thumb|Haplophrentis carinatus from the Stephen Formation, Burgess Shale (Middle Cambrian), Burgess Pass, British Columbia, Canada. Haplophrentis is a genus of tiny shelled hyolithid which lived in the Cambrian Period. Its shell was long and conical, with the open end protected by an operculum, from which two fleshy arms called helens protruded at the sides. These arms served to elevate the opening of the shells above the sea floor, acting like stilts.

Banffia is a genus of animals described from Middle Cambrian fossils. The genus commemorates Banff, Alberta, near where the first fossil specimens were discovered. Its placement in higher taxa is controversial, with it mostly being considered to be a member of the enigmatic phylum Vetulicolia.

thumb|270x270px|Agnostus sp. from the Middle Cambrian of Couloma, Hérault, France. Max Rouger Collection.

Vetulicola is an extinct genus of marine animal discovered from the Cambrian of China. It is the eponymous member of the enigmatic taxon Vetulicolia, which is of uncertain affinities but may belong to the deuterostomes. The name was derived from Vetulicola cuneata, the first species described by Hou Xian-guang in 1987 from the Lower Cambrian Chiungchussu Formation in Chengjiang, China.

thumb|Diagrammatic Reconstruction of Facivermis yunnanicus Facivermis (meaning "torch worm" ) is a genus of sessile lobopodian from the Lower Cambrian Maotianshan shales of China

thumb|Restoration Zhongjianichthys is an extinct genus of primitive jawless fish that lived in the Cambrian Period, approximately 518 million years ago, in what is now Southwest China. As a myllokunmingiid, it is considered one of the earliest known vertebrates in the fossil record alongside the other two identified genera, Haikouichthys and Myllokunmingia. Like its confamilials, its fossils were found in the Maotianshan Shales in Yunnan province.

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.

Cathaymyrus is a genus of Early Cambrian chordate known from the Chengjiang biota in Yunnan Province, China. Both species have a long segmented body with no distinctive head. The segments resemble v-shaped muscle blocks found in cephalochordates such as Amphioxus. A long linear impression runs along the "back" of the body looking something like a chordate notochord.

Siphusauctum, also known as the tulip animal, is an extinct genus of filter-feeding animals that lived during the Middle Cambrian.

Lingulella is a genus of phosphatic-shelled brachiopod. It is known from the Middle Cambrian Burgess Shale (Canada) to the Upper Ordovician Bromide Formation (United States) in North America. 346 specimens of Lingulella are known from the Greater Phyllopod bed, where they comprise 0.66% of the community.

Isoxys (meaning "equal surfaces") 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 (which are the most commonly preserved feature of the soft-bodied anatomy), and two large frontal appendages used to grasp prey.

Habelia is a genus of extinct arthropod from the Middle Cambrian, thought to be one of the earliest known relatives of chelicerates. Its fossils have been found in the Burgess Shale in British Columbia, Canada. Fifty-four specimens of Habelia are known from the Greater Phyllopod bed, where they comprise 0.1% of the community.

Lyrarapax is a radiodont genus of the family Amplectobeluidae that lived in the early Cambrian period 518 million years ago. Its fossils were found in the Maotianshan Shales of China. The first species, Lyrarapax unguispinus was described in 2014, with a second species, Lyrarapax trilobus being described in 2016, differing principally in the morphology of its frontal appendages.

left|thumb|248x248px|Fossil specimen, Geological Museum of China Cardiodictyon is a genus of lobopodian known from 518 millions years old Chengjiang Lagerstätte. 525 millions years old partial fossil is also reported. It has ~25 pairs of legs, each associated with a pair of dorsal plates.

Burgessia is a genus of arthropod known from the mid-Cambrian aged Burgess Shale of British Columbia, Canada. It is relatively abundant, with over 1,700 specimens having been collected.

Yuyuanozoon magnificissimi, from the Cambrian Stage 3 Chengjiang lagerstatte, is the largest known vetulicolian, an extinct species of marine animal, with specimens up to 20 cm in length compared to 5–14 cm for other vetulicolian species.

Pomatrum is an extinct vetulicolian, the senior synonym of Xidazoon; the latter taxon was described by Shu, et al. (1999) based on fossils found in the Qiongzhusi (Chiungchussu) Formation, Yu'anshan Member (Eoredlichia zone), Lower Cambrian, Haikou, (Kunming), about 50 km west of Chengjiang, China.

Vauxia is an extinct genus of demosponge that had a distinctive branching mode of growth. Each branch consisted of a network of strands. Vauxia also had a skeleton of spongin (flexible organic material) common to modern day sponges. Much like Choia and other sponges, Vauxia fed by extracting nutrients from the water.