The Cambrian Period is the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ago (mya) to the beginning of the Ordovician Period 485.4 mya. Its subdivisions, and its base, are somewhat in flux.
Aysheaia is an extinct genus of soft-bodied lobopodian, known from the Middle Cambrian Burgess Shale of British Columbia, Canada
Helicoplacus is the earliest well-studied fossil echinoderm. Fossil plates are known from several regions. Complete specimens were found in Lower Cambrian strata of the White Mountains of California.
Pareiasaurs are an extinct clade of large, herbivorous parareptiles. Members of the group were armoured with osteoderms which covered large areas of the body. They first appeared in southern Pangea during the Middle Permian, before becoming globally distributed during the Late Permian. Pareiasaurs were the largest reptiles of the Permian, reaching sizes equivalent to those of contemporary therapsids. Pareiasaurs became extinct at the end of the Permian during the Permian-Triassic extinction event.
Dikarya is a subkingdom of Fungi that includes the divisions Ascomycota and Basidiomycota, both of which in general produce dikaryons, may be filamentous or unicellular, but are always without flagella. The Dikarya are most of the so-called "higher fungi", but also include many anamorphic species that would have been classified as molds in historical literature. Phylogenetically the two divisions regularly group together. In a 1998 publication, Thomas Cavalier-Smith referred to this group as the Neomycota.
The "Cambrian substrate revolution" or "Agronomic revolution", evidenced in trace fossils, is a sudden diversification of animal burrowing during the early Cambrian period.
The Cambrian explosion, Cambrian radiation,Cambrian diversification, or the Biological Big Bang refers to an interval of time approximately 538.8 million years ago in the Cambrian Period of early Paleozoic when there was a sudden radiation of complex life and practically all major animal phyla started appearing in the fossil record. It lasted for about 13 – 25 million years and resulted in the divergence of most modern metazoan phyla. The event was accompanied by major diversification in other groups of organisms as well.
Leptocleididae is a family of small-sized plesiosaurs that lived during the Early Cretaceous period. They had small bodies with small heads and short necks. Leptocleidus and Umoonasaurus had round bodies and triangle-shaped heads. Leptocleidids have been found in what were shallow nearshore, freshwater and brackish habitats. Hilary F. Ketchum and Roger B. J. Benson (2010), transferred Brancasaurus, Kaiwhekea, Nichollssaura and Thililua to this family. However, Ketchum and Benson (2011) reassigned Kaiwhekea and Thililua to their original positions, as an elasmosaurid and a polycotylid, respectively.
Ancalagon minor is an extinct priapulid worm known from the Cambrian Burgess Shale.
Archaeopriapulida is a group of priapulid worms known from Cambrian lagerstätte. The group is closely related to, and very similar to, the modern Priapulids. It is unclear whether it is mono- or polyphyletic. Despite a remarkable morphological similarity to their modern cousins, they fall outside of the priapulid crown group, which is not unambiguously represented in the fossil record until the Carboniferous. In addition to well-preserved body fossils, remains of several archaeopriapulid taxa are known to have been preserved primarily as organic microfossils, such as isolated scalids and pharyngeal teeth. They are probably closely related or paraphyletic to the palaeoscolecids; the relationship between these basal worms is somewhat unresolved.
Gnathifera is a clade of generally small spiralians characterized by complex jaws made of chitin. It comprises the phyla Gnathostomulida, Rotifera and Micrognathozoa. Chaetognatha has recently been recognised as closely related to the group, with it either being included within Gnathifera or the broader group Chaetognathifera. It may also include the Cycliophora.
Aldanellidae is an extinct family of paleozoic molluscs that have been assigned to the Gastropod stem group but may also belong to a paraphyletic "Monoplacophora".
Stenothecidae is an extinct family of fossil univalved Cambrian molluscs which may be either gastropods or monoplacophorans.
In zoology, an ambulacrum is an elongated area of the shell of an echinoderm in which a row of tube feet are arranged. It is pluralized as ambulacra. The area on the shell between ambulacra is known as an interambulacrum.
Leptocleidia is a clade of plesiosauroids. The group was erected in 2007 as Leptocleidoidea. Although established as a clade, the name Leptocleidoidea implies that it is a superfamily. Leptocleidoidea is placed within the superfamily Plesiosauroidea, so it was renamed Leptocleidia by Hilary F. Ketchum and Roger B. J. Benson (2010) to avoid confusion with ranks. Leptocleidia is a node-based taxon which was defined by Ketchum and Benson as "Leptocleidus superstes, Polycotylus latipinnis, their most recent common ancestor and all of its descendants".
Stereom is a calcium carbonate material that makes up the internal skeletons found in all echinoderms, both living and fossilized forms. It is a sponge-like porous structure which, in a sea urchin may be 50% by volume living cells, and the rest being a matrix of calcite crystals. The size of openings in stereom varies in different species and in different places within the same organism. When an echinoderm becomes a fossil, microscopic examination is used to reveal the structure and such examination is often an important tool to classify the fossil as an echinoderm or related creature.
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.
Soluta is an extinct class of echinoderms that lived from the Middle Cambrian to the Early Devonian. The class is also known by its junior synonym Homoiostelea. Soluta is one of the four "carpoid" classes, alongside Ctenocystoidea, Cincta, and Stylophora, which made up the obsolete subphylum Homalozoa. Solutes were asymmetric animals with a stereom skeleton and two appendages, an arm extending anteriorly and a posterior appendage called a homoiostele.
Ctenocystoidea is an extinct clade of echinoderms, which lived during the Cambrian and Ordovician periods. Unlike other echinoderms, ctenocystoids had bilateral symmetry, or were only very slightly asymmetrical. They are believed to be one of the earliest-diverging branches of echinoderms, with their bilateral symmetry a trait shared with other deuterostomes. Ctenocystoids were once classified in the taxon Homalozoa, also known as Carpoidea, alongside cinctans, solutes, and stylophorans. Homalozoa is now recognized as a polyphyletic group of echinoderms without radial symmetry. Ctenocystoids were geographically widespread during the Middle Cambrian, with one species surviving into the Late Ordovician.
This is a list of the biota of the Burgess Shale, a Cambrian lagerstätte located in Yoho National Park in Canada.
