symplesiomorphy, n. Taxon.
Brit. /sɪmˈpliːzɪə(ʊ)mɔːfi/, U.S. /sɪmˈplisiəˌmɔrfi/
[‹ sym- prefix + plesio- comb. form + -morphy comb. form. Compare slightly later symplesiomorphic adj.]
The possession by two or more organisms or taxa of a shared primitive or ancestral character not exclusive to or characteristic of them in particular; the shared character itself. Cf. synapomorphy n. at syn- prefix Affix 1
| 1959 Systematic Zool. 8 118/1 Either characters are plesiomorphic..or are apomorphic..and their value for the classification varies according to their nature (symplesiomorphy, synapomorphy, autapomorphy, etc.). 1988 I. Tattersall et al. Encycl. Human Evol. & Prehist. 135/2 The placenta is a synapomorphy of placental mammals but is a symplesiomorphy (shared primitive character) when two mammalian groups (e.g. Rodentia and Primates) are being compared. 1990P. C. Sereno in K. Carpenter & P. J. Currie Dinosaur Systematics (1992) i. 10 Nearly all systematists now agree that phylogenetic affinity can only be inferred from synapomorphies and not from symplesiomorphies. 2002 S.J. Gould Struct. Evolutionary Theory x. 1132 Rhodopsin operates in sensitivity towards light in all three multicellular kingdoms—suggesting a symplesiomorphy of great phyletic depth. |