Search results
Results From The WOW.Com Content Network
The crown age of a clade refers to the age of the most recent common ancestor of all of the species in the clade. The stem age of a clade refers to the time that the ancestral lineage of the clade diverged from its sister clade. A clade's stem age is either the same as or older than its crown age. [15] Ages of clades cannot be directly observed.
SAR or Harosa is a highly diverse clade of eukaryotes, often considered a supergroup, [2] that includes stramenopiles (heterokonts), alveolates, and rhizarians. [3] [4] [5] It is a node-based taxon, including all descendants of the three groups' last common ancestor, [6] and comprises most of the now-rejected Chromalveolata. [2]
It is thus a way of defining a clade, a group consisting of a species and all its extant or extinct descendants. For example, Neornithes (birds) can be defined as a crown group, which includes the most recent common ancestor of all modern birds, and all of its extant or extinct descendants.
The CAM clade is a clade containing the Archaeplastida (Plantae sensu lato) and the clade Pancryptista (which, in turn, contains Cryptista and Microheliella maris).This clade is supported by phylogenomic analyses from 2022 that mainly support the clade Pancryptista, but also mention that Archaeplastida's closest lineage is Pancryptista, making them sister taxa. [1]
Willi Hennig 1972 Peter Chalmers Mitchell in 1920 Robert John Tillyard. The original methods used in cladistic analysis and the school of taxonomy derived from the work of the German entomologist Willi Hennig, who referred to it as phylogenetic systematics (also the title of his 1966 book); but the terms "cladistics" and "clade" were popularized by other researchers.
The clade shown by the dashed lines in each figure is specified by the ancestor X. Using the hypothesis that the relationships are as in the left tree diagram, the clade includes X, A, B and C. Using the hypothesis that the relationships are as in the right tree diagram, the clade includes X, A and B.
The term sister group is used in phylogenetic analysis, however, only groups identified in the analysis are labeled as "sister groups".. An example is birds, whose commonly cited living sister group is the crocodiles, but that is true only when discussing extant organisms; [3] [4] when other, extinct groups are considered, the relationship between birds and crocodiles appears distant.
One study based on DNA analysis suggests that Scandentia and Primates are sister clades, but does not discuss the position of Dermoptera. [9] Although it is known that Scandentia is one of the most basal Euarchontoglires clades, the exact phylogenetic position is not yet considered resolved, and it may be a sister of Glires, Primatomorpha or Dermoptera or to all other Euarchontoglires.