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Reference.org
Plesiomorphy and symplesiomorphy
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<p>In <a href="/facts/Phylogenetics/bw4rsovt">phylogenetics</a>, a plesiomorphy ("near form") and symplesiomorphy are synonyms for an ancestral <a href="/facts/Phenotypic_trait/seYSUTul">character</a> shared by all members of a <a href="/facts/Clade/XefyYmWn">clade</a>, which does not distinguish the clade from other clades. </p><p>Plesiomorphy, symplesiomorphy, <a href="/facts/Apomorphy_and_synapomorphy/t21GWRl1">apomorphy, and synapomorphy</a> all mean a trait shared between species because they share an ancestral species. </p><p>Apomorphic and synapomorphic characteristics convey much information about evolutionary clades and can be used to define taxa. However, plesiomorphic and symplesiomorphic characteristics cannot. </p><p>The term <i>symplesiomorphy</i> was introduced in 1950 by German <a href="/facts/Entomology/zTtUNTWm">entomologist</a> <a href="/facts/Willi_Hennig/HtLMfBY9">Willi Hennig</a>. </p>