Palaeos: Palaeos Cladistics
and systematics

Definition: Monophyly

Monophyletic Taxa

monophyletic taxon
graphic © Darren Abbey

The Monophyletic taxon,also called a clade, is the building block of the cladistic system of taxonomy.  It refers to any group of organisms that includes the most recent common ancestor of all those organisms and all the descendants of that common ancestor.

Examples:  Insects, Vertebrates, Mammalia, Angiosperms, etc, etc.

A definition of monophyly, from Glossary of Phylogenetic Systematics by Günter Bechly:

"monophyletic group (= monophylum): In a hierarchical system of descent, an ancestor (stem-species) and all of his descendants (descendant species) together form a closed community of descent that is called a monophyletic group (sensu HENNIG; = holophyletic group sensu ASHLOCK) or monophylum. Monophyletic groups can be discovered (not defined!) by synapomorphies. The term monophyly is always referring to groups of hierarchically reproducing entities (species) and consequently can not be applied to (or within) a single biospecies or even to a single organism..."
© Günter Bechly

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non-quoted text by M. Alan Kazlev (Creative Commons Attribution 3.0 Unported License), cladogram graphic © Darren Abbey, reproduced with permission
page uploaded 20 May 2002 (originally uploaded on Kheper Site 13 November 1998)
checked ATW040703 last modified MAK090828, edited RFVS111203