Also found in: Dictionary, Thesaurus, Encyclopedia, Wikipedia.
n. pl. plesiomor·phies
An evolved character or trait that is shared by some or all members of a phylogenetic group and their common ancestor but is not unique to that group. A segmented spinal column is a plesiomorphy of mammals, being present as well in other groups such as fishes, reptiles, amphibians, and birds.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.