For spiders, morphological differentiation within genitalic traits is the main diagnostic criterion of a species. Beside some well-described exceptions of genitalic polymorphism and crypticity, spider genitalic variation is seldom quantitatively analyzed. Using geometric morphometrics landmark analysis, we report clear evidence of quantitative interspecific divergence and intraspecific variation in the genital shape of three species of the genus Paratrechalea (P. azul, P. ornata and P. galianoae). The genitalic species recognition was very consistent with our quantitative data for both sexes. Interspecific variation suggested a character displacement pattern between two syntopic populations of P. azul and P ornata, and also a possible case of species crypticity in P. ornata that will involve splitting the Uruguayan populations from the Brazilian ones.