Quantitative handling of characters useful in snake systematics with particular reference to intraspecific variation in the Ringed Snake Natrix natrix (L.)

This paper is based on the numerous characters used in a biometric study of the intraspecific variation of Natrix natrix (L.). These characters are drawn from the internal morphology, scalation, colour pattern, body proportions, dentition and dermal sense organs. The criteria involved in selecting these characters for taxonomic work are considered. The alternative methods for quantifying the above features are discussed and so are the theoretical problems involved in coding the continuous characters. The value of the characters in studying the geographic variation, ontogenetic variation and sexual dimorphism in N. natrix is indicated. The use of a wider range of characters than just the scalation and colour pattern is urged when diagnosing the lower taxonomic levels of ophidians. The neglected internal morphology may well be able to supply characters to this end.