Taxonomy
C
Clade
/ /kleɪd/ /
Etymology:
From Greek klados — "branch"
Quick Definition
A monophyletic group comprising an ancestor and all of its descendants, as shown on a phylogenetic tree.
📖 Full Definition
A clade (also called a monophyletic group) includes a single common ancestor and all organisms descended from it. Cladistics is the methodology of classifying organisms based entirely on their inferred evolutionary history (phylogeny), with all taxa being clades. Modern fish systematics uses molecular phylogenies to define and diagnose clades. Traditional Linnaean ranks (order, family) do not necessarily correspond to clades — many traditional fish "groups" (e.g. "sharks," "bony fishes") are grades, not clades, because they exclude some descendants.
💡 Examples & Context
"Reptilia" as classically defined is not a clade because it excludes birds, which are descended from dinosaurs — a reptile group. "Tetrapoda" is a true clade.