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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.
A clade located within a clade is said to be nested within that clade. In the diagram, the hominoid clade, i.e. the apes and humans, is nested within the primate clade. Two clades are sisters if they have an immediate common ancestor. In the diagram, lemurs and lorises are sister clades, while humans and tarsiers are not.
In terms of mtDNA, however, it appears that modern humans and Neanderthals form a sister clade, with Denisovans as basal outgroup. The split of Neanderthal and modern human mtDNA is dated to about 498–295 kya, i.e. significantly younger than the date estimated based on nuclear DNA.
One small clade of fish, showing how venom has evolved multiple times. [10]Taxonomy is the identification, naming, and classification of organisms. Compared to systemization, classification emphasizes whether a species has characteristics of a taxonomic group. [6]
Amborella trichopoda, the most basal extant angiosperm. The flowering plant family Amborellaceae, restricted to New Caledonia in the southwestern Pacific, [n 9] is a basal clade of extant angiosperms, [13] consisting of the most species, genus, family and order within the group that are sister to all other angiosperms (out of a total of about 250,000 angiosperm species).
Haplogroup R, or R-M207, is a Y-chromosome DNA haplogroup.It is both numerous and widespread among modern populations. Some descendant subclades have been found since pre-history in Europe, Central Asia and South Asia.
Clade T is a total group or pan-group, its extant species organized into crown groups C1 and C2.Within clade T are sister clades T1 and C2. Clade T1 is composed of crown group C1 and the stem group S1 which is the set of extinct species that are closer to C1 than any other crown group of extant species.
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.