Micro-computed tomography is a powerful tool towards the detailed reconstruction of internal and external morphology, in particular for ossified and other dense tissues. Here, we document and compare the amount of calcification in the skin of the head and the parotoids (the external skin glands) in males and females of the common and spined toads, Bufo bufo and B. spinosus. In some anurans including Bufo species, a specific acellular calcified tissue layer (the Eberth-Katschenko layer) within the dermis has been documented. Using micro-CT scan and standard histological techniques, we detected additional calcium deposits located in the dermal layer stratum spongiosum, above the Eberth-Katschenko layer. The data show that the level of calcification and the presence of the additional calcium deposits is size- and sex-related, increasing in the order from B. bufo males, B. spinosus males, B. bufo females to B. spinosus females. The least variable are B. spinosus females that have dense additional calcium deposits in parotoids, dorsal and ventral skin, as armour protecting their heads. Three-dimensional volume renderings and cross-sectional slices obtained by micro-CT scan used in this study indicate that this approach is a promising technique for further studies on Bufo skin anatomy and geographic variation in skin calcification.

Bufo bufo and B. spinosus collection material were analyzed to estimate the calcification level in the head skin. Information on species, sex and locality are provided. The dataset ID corresponds to files containing individual's trans-axial slices of the head region obtained with a high-resolution micro-CT scanner (Xradia Versa 520, Carl Zeiss X-Ray Microscopy Inc., Pleasanton, CA, USA, in Naturalis Biodiversity Centre, Leiden, The Nederlands). Museum code: ZMA.RenA, Naturalis Biodiversity Center, Leiden, The Netherlands. 

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