Definition of autapomorphy
: a specialized character or trait that is unique to a monophyletic taxonomic group … An eversible penis is a synapomorphy that unites lizards and snakes in a common monophyletic group, the Squamata, but is an autapomorphy of the Squamata within a larger monophyletic assemblage. — Robert L. Carroll, Patterns and Processes in Vertebrate Evolution, 1997 These species share key traits as autapomorphies of their clade—and since these traits help to construct the relevant environment, sufficient similarity becomes, in part, an active construction of related organisms, not only a happenstance of common externalities. — Stephen Jay Gould, The Structure of Evolutionary Theory, 2002
autapomorphous\ȯ-ˌta-pə-ˈmȯr-fəs\ play adjective The Chondrichthyes are a monophyletic clade and are principally distinguished on the basis of two unique autapomorphous character sets. — Eileen D. Grogan and Richard Lund, in Biology of Sharks and their Relatives, 2004
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