Fig. 1
From: Digit ratio in the common toad Bufo bufo: the effects of reduced fingers and of age dependency
Two alternative finger numbering protocols for anuran forelimbs, reflecting the hypotheses that the fifth (variant I) or the first (variant II) digit was reduced during phylogenesis. The upper and lower parts of the figure show which fingers are used to measure digit ratios in each of the adopted protocols, with the results presented in the form of box plots. It should be noted that 2D:3D in variant I corresponds to 3D:4D in variant II; similarly, 2D:4D corresponds to 3D:5D, and 3D:4D corresponds to 4D:5D. Although variant I is predominantly used in research, it is variant II that probably reflects the actual finger numbering in anurans (see in text: Limb and finger development in anurans). Asterisks indicate the statistical significance level of the difference in digit ratios between sexes (gray box plots - male; white box plots – female; levels of significance: ***p < 0.001, **p < 0.01). The illustration of an anuran forelimb was adapted from [27]