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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.
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 ...
The group that includes mammals and birds, both "warm-blooded" homeothermic animals (in red) is polyphyletic. Homeothermy, homothermy or homoiothermy [1] is thermoregulation that maintains a stable internal body temperature regardless of external influence.
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 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.
Cladogram (family tree) of a biological group. The last common ancestor is the vertical line stem at the bottom. The blue and orange subgroups are clades; each shows its common ancestor stem at the bottom of the subgroup branch.
Pachydermata is an obsolete order of mammals described by Gottlieb Storr, Georges Cuvier, and others, at one time recognized by many systematists.The grouping is polyphyletic, so the order is no longer in use as a biological classification.