A Palearctic green toad from the Bufo viridis subgroup (see Stöck et al. 2006 for details). This species is a medium- to large-sized green toad that differs from all others, especially all circum-Mediterranean green toad species, by its distinct mitochondrial haplotype group. Bufo siculus exhibits strong variability in coloration with adult males showing less contrast in marbled patterns than females. Brownish to olive (but barely bright greenish) spots often form light dorsal stripes (not to be confused with a yellowish pigmented stripe), a character rarely found in other green toads of Italy, but which is quite common in B. boulengeri from North Africa. The new species is distinguishable from its geographic neighbor, B. balearicus, which exhibits pinhead-sized red (female B. balearicus) or brownish (male B. balearicus) spots around tips of lateral glands, by the lack of these spots. Bufo siculus almost never shows a reddish-orange coloration, characteristic of many B. balearicus, the only form of the subgroup with which it may co-occur on Sicily. In Sicily, the ratio VDT/ ED [vertical diameter of the tympanum (VDT) divided by the diameter of the eye (ED)] is smaller in B. siculus [0.530 (max) ≥ 0.381 (mean) ≤ 0.247 (min) (N = 42)] than in allo- or parapatric B. balearicus [0.622 ≥ 0.478 ≤ 0.345 (N = 31)], but similar to that of African B. boulengeri [0.527 ≥ 0.362 ≤ 0.25 (N = 29)]. In life, B. siculus has a dark yellowish-golden iris.
Taken with permission from Stöck et al. (2008). See open-access journal article at: http://www.biomedcentral.com/1471-2148/8/56