The Rostroconchia is a class of extinct molluscs dating from the early Cambrian to the Late Permian. They were initially thought to be bivalves, but were later given their own class. They have a single shell in their larval stage, and the adult typically has a single, pseudo-bivalved shell enclosing the mantle and muscular foot. The anterior part of the shell probably pointed downward and had a gap from which the foot could probably emerge. Rostroconchs probably lived a sedentary semi-infaunal lifestyle. There were probably more than 1,000 species of members of this class.
The small shelly fauna, small shelly fossils (SSF), or early skeletal fossils (ESF) are mineralized fossils, many only a few millimetres long, with a nearly continuous record from the latest stages of the Ediacaran to the end of the Early Cambrian Period. They are very diverse, and there is no formal definition of "small shelly fauna" or "small shelly fossils". Almost all are from earlier rocks than more familiar fossils such as trilobites. Since most SSFs were preserved by being covered quickly with phosphate and this method of preservation is mainly limited to the late Ediacaran and early Cambrian periods, the animals that made them may actually have arisen earlier and persisted after this time span.
Radiodonta is an extinct order of stem-group arthropods that was successful worldwide during the Cambrian period. They may be referred to as radiodonts, radiodontans, radiodontids, anomalocarids, or anomalocaridids, although the latter originally refer to the family Anomalocarididae, which previously included all species of this order but is now restricted to only a few species. Radiodonts are distinguished by their distinctive frontal appendages, which are morphologically diverse and used for a variety of functions. Radiodonts included the earliest large predators known, 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 gainessii, Cambroraster falcatus and Amplectobelua symbrachiata, the Ordovician Aegirocassis benmoulai and the Devonian Schinderhannes bartelsi.
Tommotiids are Cambrian (Terreneuvian) shelly fossils thought to belong to the Brachiopod + Phoronid lineage (Brachiozoa).
The origin of the brachiopods is uncertain; they either arose from reduction of a multi-plated tubular organism, or from the folding of a slug-like organism with a protective shell on either end. Since their Cambrian origin, the phylum rose to a Palaeozoic dominance, but dwindled during the Mesozoic.
The palaeoscolecids are a group of extinct ecdysozoan worms resembling armoured priapulids. They are known from the Lower Cambrian to the late Silurian; they are mainly found as disarticulated sclerites, but are also preserved in many of the Cambrian lagerstätten. They take their name from the typifying genus Palaeoscolex. Other genera include Cricocosmia from the Lower Cambrian Chengjiang biota.
Stenothecoida is a taxon of bivalved fossils from the Early to middle Cambrian period. They look a bit like brachiopods or bivalve molluscs.
Mongolitubulus is a form genus encapsulating a range of ornamented conical small shelly fossils of the Cambrian period. It is potentially synonymous with Rushtonites, Tubuterium and certain species of Rhombocorniculum, and owing to the similarity of the genera, they are all dealt with herein. Organisms that bore Mongolitubulus-like projections include trilobites, bradoriid arthropods and hallucigeniid lobopodians.
Eccentrotheca is a genus of sclerite-bearing marine organism known from Cambrian deposits. Its sclerite form rings that are stacked to produce a widening-upwards conical scleritome. Individual plates have been homologized with the valves of brachiopods, and a relationship with the phoronids is also likely at a stem-group level. Its pointed end terminated in a stub that probably fastened it to a hard sea floor; its open end has been interpreted as a filter-feeding aperture.
Watsonella is a genus of 'mollusc' known from early (Terreneuvian) Cambrian strata.
Mickwitziids are a Cambrian group of shelly fossils with originally phosphatic valves, belonging to the Brachiopod stem group, and exemplified by the genus Mickwitzia – the other genera are Heliomedusa and Setatella. The family Mickwitziidae is conceivably paraphyletic with respect to certain crown-group brachiopods.
The Shackleton Limestone is a Cambrian limestone formation of the Byrd Group of Antarctica. The age of the formation is established to be Cambrian Stage 3, dated at ranging from 520 to 516 Ma. This period correlates with the End-Botomian mass extinction. Fossils of trilobites and Marocella mira and Dailyatia have been found in the formation, named after Ernest Shackleton, who led a failed expedition into Antarctica. At time of deposition, the Antarctic Plate has been established to be just south of the equator as part of the supercontinent Pannotia, contrasting with its present position at 82 degrees southern latitude.
Pseudorhabdosynochus americanus is a diplectanid monogenean parasitic on the gills of groupers. It was described as Diplectanum americanum by Price in 1937 and transferred to the genus Pseudorhabdosynochus by Kritsky and Beverley-Burton in 1986. The species was redescribed by Kritsky, Bakenhaster and Adams in 2015.
Pseudorhabdosynochus justinella is a diplectanid monogenean parasitic on the gills of the red grouper, Epinephelus morio. It has been described by Kritsky, Bakenhaster and Adams in 2015.
Pseudorhabdosynochus sulamericanus is a diplectanid monogenean parasitic on the gills of the snowy grouper, Epinephelus niveatus, the Warsaw grouper, Epinephelus nigritus and the Haifa grouper, Epinephelus haifensis. It has been described by Santos, Buchmann & Gibson in 2000 , redescribed by Kritsky, Bakenhaster and Adams in 2015. and again redescribed by Chaabane, Justine, Gey, Bakenhaster & Neifar in 2016.
Cincta is an extinct class of echinoderms that lived only in the Middle Cambrian epoch. Homostelea is a junior synonym. The classification of cinctans is controversial, but they are probably part of the echinoderm stem group.
Tannuolina is a genus of tommotiid, belonging to the brachiopod stem lineage.
Micrina is an extinct genus of tommotiids with affinities to brachiopods.
Left-right asymmetry, (LR asymmetry) is the process in early embryonic development that breaks the normal symmetry in the bilateral embryo. In vertebrates, left-right asymmetry is established early in development at a structure called the left-right organizer and leads to activation of different signalling pathways on the left and right of the embryo. This in turn cause several organs in adults to develop LR asymmetry, such as the tilt of the heart, the different number lung lobes on each side of the body and the position of the stomach and spleen on the right side of the body. If this process does not occur correctly in humans it can result in the syndromes heterotaxy or situs inversus.
Collinsovermis is a genus of extinct worm belonging to the group Lobopodia and known from the middle Cambrian Burgess Shale in British Columbia, Canada. It is monotypic having only one species, Collinsovermis monstruosus. After its initial discovery in 1983, Desmond H. Collins popularised it as a unique animal and was subsequently dubbed "Collins' monster" for its unusual super armoured body. The formal scientific description and name were given in 2020.
