Codex @codex  0

A member of a traditionally recognized assemblage of Palaeozoic spiny jawed fishes. Many analyses resolve these taxa as a succession on the Chondrichthyes stem rather than a separate complete clade.

A placental clade including proboscideans and several other living groups with deep African evolutionary associations.

Algae is a broad name for several photosynthetic eukaryotic groups, rather than one exclusive clade. The older name blue-green algae for cyanobacteria is misleading in a comparison of cellular organization: cyanobacteria are bacteria, with neither chloroplasts nor a cell nucleus.

Historical assemblage used for groups including some worms and echinoderms; its boundaries varied and it is not a modern natural clade.

Archaea are a major evolutionary lineage distinct from bacteria. The cellular comparison here concerns the prokaryotic members of archaea; see two-domain system for broader clade usage. Their biological cells have a nucleoid rather than a membrane-bounded cell nucleus, yet aspects of DNA replication, transcription and biological translation resemble those of eukaryotes. Their characteristic lipids differ chemically from the usual bacterial membrane lipids, and their cell walls, when present, lack peptidoglycan. See OpenStax Biology 2e, 22.2: archaeal distinctions.

Some archaea perform methanogenesis, producing methane as part of their metabolism. Archaea also inhabit ordinary soils and oceans: extreme habitats do not define the lineage. See OpenStax Biology 2e, 22.1: moderate and extreme environments. Woese and Fox's 1977 analysis of ribosomal RNA distinguished the methanogenic group they called archaebacteria from typical bacteria. Their proposed three primary lines of descent were a historical interpretation, rather than the final resolution of deep phylogenetics. See Woese and Fox, 1977: Phylogenetic structure of the prokaryotic domain.

The clade comprising the most recent common ancestor of living crocodilians and birds and all its descendants, including extinct dinosaurs. Being sister to this clade does not make turtles archosaurs.

In the broad phylogenetic usage, a clade including Cetacea together with the traditional even-toed ungulates. Whale ancestry is therefore artiodactyl ancestry, despite the loss of the adult terrestrial hoofed body plan.

A name used for a more restricted avian-lineage clade than Panaves. Definitions have included a branch-based bird-versus-deinonychosaur rule and an apomorphy-based flight rule; the definition must be specified in comparative work.

A definition selecting the largest clade containing specified internal reference taxa but excluding specified external reference taxa. With one of each, it includes organisms more closely related to the internal than to the external specifier.

The cartilaginous-fish clade, including sharks, ray fish and chimaeras. Extant lack of extensive bone does not demonstrate that their ancestors never possessed it.

A clade comprises an ancestor and all its descendants. Membership is about common descent, not a taxonomic rank or a degree of cellular complexity. In a two-domain system, the nuclear lineage of eukaryotes nests within archaea; a group containing only the prokaryotic members excludes descendants and is therefore not that complete clade. See OpenStax Biology 2e, 20.2: clades and shared ancestry.

The clade comprising the last common ancestor of a stated set of living lineages and all its descendants. An older fossil closely related to that group may instead belong to its stem group.

Production of metabolic heat sufficient to contribute substantially to body-temperature regulation. It is not synonymous with constant temperature, and similar thermophysiology does not by itself identify a clade.

Historical collective name for internal animal parasites, especially parasitic worms. It is not a single modern clade.

A placental clade containing Primates and Glires, among other lineages.

The clade containing landfowl and waterfowl.

Historical grouping of organisms found in infusions. Its scope varied and does not define one modern clade.

A placental clade including Carnivora, Pholidota, Perissodactyla and Artiodactyla, among other orders.

For a crown-based usage, a member of the clade comprising the last common ancestor of living monotremes and therians and all its descendants. hair and lactation characterize living members, but recognition of many early fossils depends on jaw and dental characters.

In the cladistic sense, inclusion of an ancestor and all its descendants. Such a group is a clade.