monophyla

Monophyla is a term used in some biological classifications to denote a monophylum, a group that descends from a single common ancestor and includes all of that ancestor's descendants. In modern cladistics, the equivalent concept is a monophyletic group or clade. The plural form monophyla comes from Greek roots meaning “single race.”

In usage, monophyla can appear in historical or taxonomically oriented writings, but contemporary practice typically prefers the term monophyletic group to describe the property, and clade to name the group itself. The essential idea is that a monophylum represents an evolutionary lineage that is complete, containing the common ancestor and every descendant, with no exclusions.

Monophyla is distinguished from paraphyla (paraphyletic groups), which omit some descendants of the most recent common ancestor, and from polyphyla (polyphyletic groups), which collect descendants from multiple, distant ancestors. Because of these distinctions, the concept of a monophylum underpins attempts to reflect evolutionary relationships in classification.

Examples often cited as monophyletic include major animal and plant lineages such as Mammalia or Angiospermae, which in current understanding are treated as clades that include all descendants of their most recent common ancestor. In practice, taxonomists may refer to these groups by their clade names and describe their monophyly rather than using the explicit taxon name Monophyla. The term remains a historical or alternative phrasing for the same fundamental concept.