Glossary of "Cladistics (2nd ed.)" by Kitching et al. (1998)
- A coding to denote character states that cannot logically be observed in some taxa (e.g. the condition of tooth characters in modern turtles). Computer programs evaluate these as missing data coded as question marks. Also known as illogical coding.
- Kitching, I. J., Forey, P. L. Humphries, C. J. & Williams, D. M. 1998. Cladistics, 2nd ed.: the Theory and Practice of Parsimony Analysis. -xii + 228 pp. Oxford University Press, New York.