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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.
Whippomorpha is a suborder located within the Order Artiodactyla, and the clade Cetancodontamorpha. It contains the clades Hippopotamoidea (ancestors of hippopotamuses) and Cetaceamorpha (ancestors of whales and dolphins). Whippomorpha is considered a sister clade to Ruminantia (which contains cattle, sheep and deer), as well as the extinct ...
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.
Branches down to the divergence to the next significant (e.g. extant) sister are considered stem-groupings of the clade, but in principle each level stands on its own, to be assigned a unique name. For a fully bifurcated tree, adding a group to a tree also adds an additional (named) clade, and a new level on that branch.
Overall, studies using mitochondrial DNA have tended to group them as a sister clade to Ferungulata (carnivorans+ungulates+pholidotans), while studies using nuclear DNA have identified them as 1) a sister clade to Afrotheria, 2) a sister clade to all placentals except Afrotheria, or 3) a trichotomy (three-way split): Afrotheria, Xenarthra, and ...
A case of clade I mpox has been confirmed in California, the Centers for Disease Control and Prevention said on Saturday, marking the first case of the strain the United States. The CDC said the ...
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.
An mpox case in Sweden this month prompted the World Health Organization to declare a public health emergency, but the potentially-deadly strain of the virus has not yet made it to the United ...