plesiomorphy


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Related to plesiomorphy: Cladistic analysis, Plesiomorphic

plesiomorphy

(plē′sē-ə-môr′fē, plē′zē-)
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.

ple′si·o·mor′phic adj.
References in periodicals archive ?
It can be considered as a plesiomorphy, because there is no other evidence on the existence of a close relationship among these three taxa or it can be considered as a convergence character; the long III segment (long labium) has developed independently in these groups.
Concluding that the dicotyledonous embryo is a plesiomorphy among seed plants implies that the monocotyledonous embryo of monocots is a distinctive autapomorphy for this class of angiosperms.
The presence of only one gland type in the adhesive organ is interpreted as a plesiomorphy when viewed in combination with the retention of other primitive traits (Tyler et al., 1980).
(1995) - specifically, the resolution of Anomochloa and Streptochaeta as elements of the earliest lineage of grasses to diverge from the line that includes all others - the pseudospikelets present in these taxa can be regarded either as a synapomorphy of this lineage (i.e., Anomochlooideae) or as a plesiomorphy of the grasses that is retained only in these two genera, though in modified form in Streptochaeta (Judziewicz & Soderstrom, 1989).