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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.
Captorhinidae was transferred to Eureptilia, while Parareptilia included turtles alongside many of the taxa named as such by Gauthier et al. (1988). There was one major exception: mesosaurs were placed outside both groups, as the sister taxon to the crown group Reptilia. Mesosaurs were still considered sauropsids, as they were closer to ...
Gnathifera is a member of Spiralia. It is the sister taxon of a clade comprising all other spiralians. [1] [19] An alternative phylogeny place Gnathifera into a main spiralian clade Platyzoa s.l. as sister clade to Mesozoa and Platyhelminthes. [21]
The term paraphyly, or paraphyletic, derives from the two Ancient Greek words παρά (pará), meaning "beside, near", and φῦλον (phûlon), meaning "genus, species", [2] [3] and refers to the situation in which one or several monophyletic subgroups of organisms (e.g., genera, species) are left apart from all other descendants of a unique common ancestor.
In a 2012 molecular study, von Reumont et al. challenge the monophyly of Vericrustacea: they present four versions of Pancrustacea cladogram (figures 1–4), and in all four figures Remipedia is a sister group to Hexapoda, and Branchiopoda is a sister group to (Remipedia + Hexapoda). Thus, their data strongly suggest that Branchiopoda is more ...
The name plesion has a long history in biological systematics, and plesion group has acquired several meanings over the years. One use is as "nearby group" (plesion means close to in Greek), i.e. sister group to a given taxon, whether that group is a crown group or not. [22]
A concept based on purely morphological characteristics pictures the Placozoa as the nearest relative of the animals with true tissues . The taxon they share, called the Epitheliozoa , is itself construed to be a sister group to the sponges ( Porifera ):
In the late 20th century, it was recognized that the order Thysanura was paraphyletic, thus the two suborders were each raised to the status of an independent monophyletic order, with Archaeognatha sister taxon to the Dicondylia, including the Zygentoma. [5] The order Archaeognatha is cosmopolitan; it includes roughly 500 species in two ...