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"group of organisms evolved from a common ancestor," 1957, from Greek klados "young branch, offshoot of a plant, shoot broken off," from PIE *kele-, possibly from root *kel- "to strike, cut" (see holt).
A grouping of organisms made on the basis of phylogenetic relationship, rather than purely on shared features. Clades consist of a common ancestor and all its descendants. The class Aves (birds) is a clade, whereas the class Reptilia (reptiles) is not, since it does not include birds, which are descended from the dinosaurs, a kind of reptile. Many modern taxonomists prefer to use clades in classification, and not all clades correspond to traditional groups like classes, orders, and phyla. Compare grade.