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A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. [1] The term is often applied to groups that share similar features known as homoplasies , which are explained as a result of convergent evolution .
In taxonomy, a group is polyphyletic if it consists of clades from multiple separate branches of the tree of life, not forming a complete clade. This classification is often due to phenotypes that have converged or reverted so as to appear to be the same but which have not been inherited from common ancestors.
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.
A polyphyletic assemblage is one which is neither monophyletic nor paraphyletic. A polyphyletic assemblage is characterized by one or more homoplasies: character states which have converged or reverted so as to be the same but which have not been inherited from a common ancestor. No systematist recognizes polyphyletic assemblages as ...
Thus the thelodonts are generally thought to represent a polyphyletic group, [12] although there is no firm agreement on this point; if they are monophyletic, there is no firm evidence on what their ancestral state was.
The term monophyly, or monophyletic, derives from the two Ancient Greek words μόνος (mónos), meaning "alone, only, unique", and φῦλον (phûlon), meaning "genus, species", [4] [5] and refers to the fact that a monophyletic group includes organisms (e.g., genera, species) consisting of all the descendants of a unique common ancestor.
The term "clade" was coined in 1957 by the biologist Julian Huxley to refer to the result of cladogenesis, the evolutionary splitting of a parent species into two distinct species, a concept Huxley borrowed from Bernhard Rensch.
The Thermoanaerobacterales is a polyphyletic order of bacteria placed within the polyphyletic class Clostridia, and encompassing four families: the Thermoanaerobacteraceae, the Thermodesulfobiaceae, the Thermoanaerobacterales Family III. Incertae Sedis, and the Thermoanaerobacterales Family IV.