plesiomorphicadj.
/ˌpliːzɪəˈmɔːfɪk/, U.S. /ˈˌplisiəˈmɔrfɪk/ΘΚΠ
the world > matter > chemistry > crystallography (general) > crystal (general) > structures and forms > [adjective] > plesiomorphous
plesiomorphous1832
plesiomorphic1849
1849 H. McMurtrie Lexicon Scientiarum Plesiomorphic.., applied to Crystals of which the form is nearly similar.
1854 J. W. Draper Kane's Elements Chem. (Amer. ed.) 225 By change of figure, when brought to ordinary temperatures, the small plesiomorphic differences may have occurred.
2. Taxonomy. Of a trait or characteristic: primitive and ancestral; spec. present in organisms outside a clade or group under consideration, and so not distinctively characteristic of members of that clade or group (and presumed to derive from a more distant common ancestor). Cf. plesiomorphous adj. 2. Opposed to apomorphic.
ΚΠ
1959 Systematic Zool. 8 117 Characters are either plesiomorphic (= primitive, generalized, conservative, and so on), or are apomorphic (= derived, specialized, progressive, and so on).
1970 Geogr. Rev. 60 415 Methods of character analysis used in currently popular numerical taxonomy frequently result in significant associations between plesiomorphic characters.
1983 Systematic Bot. 8 318 Greater leaf-cushion height than width appears to be plesiomorphic and thus of limited usefulness.
2002 S. J. Gould Struct. Evolutionary Theory x. 1167 [One of] the two canonical and most anatomically extensive examples of evolution from homonomy to regional specialization and complexity in the evolution of insects and other arthropods—evolution from the plesiomorphic state of walking legs on all post-oral segments.
This entry has been updated (OED Third Edition, September 2006; most recently modified version published online March 2022).
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adj.1849