2016), alligators (Vickaryous and Hall, 2008) and lizards (Zylberberg and Castanet, 1985 Levrat‐Calviac and Zylberberg, 1986 Vickaryous et al. However, in reptiles, including dinosaurs (e.g. in Dasypus novemcinctus (Linnaeus, 1758), the nine‐banded armadillo, is comparable with intramembranously derived elements of the human skull (Vickaryous and Sire, 2009). Previous work has shown that OD development is not homogenous across vertebrates (Vickaryous and Sire, 2009) the mode of development of some ODs in mammals, e.g. 2011), evolutionary origin, and homology across species (de Buffrénil et al. The histological organisation of skeletally mature ODs provides information about their mode of development (Moss, 1972 de Buffrénil et al. They are often referred to as 'ossicles', 'bony plates' or 'dermal armour', among other synonyms. Osteoderms (ODs), a term which literally means 'bone in the skin', are hard tissue organs embedded into the dermis of vertebrates (Moss, 1972), forming part of the dermal (integumentary) skeleton of tetrapods (Vickaryous and Sire, 2009). These data allow greater understanding of the comparative histological appearance of the dermal bones of lizards and highlight their structural diversity. The histology of the mineralised tissues observed in these two reptile taxa provides insights into the mechanism of formation of lizard ODs and presents a direct comparison of the histological properties between the ODs of the two species. Thus, in these two species, ODs differ both in terms of their structural composition and in details of their skeletogenesis. komodoensis are composed of a core of woven bone surrounded by parallel‐fibred bone without a capping tissue. suspectum are composed of three main tissue types, a superficial layer, herein identified as osteodermine, capping a base composed of Sharpey‐fibre bone and lamellar bone rich in secondary osteons (Haversian bone tissue). Histological analysis showed that the ODs of H. We describe the histological appearance of the osteoderms (ODs) of Heloderma suspectum and Varanus komodoensis using multiple staining and microscopy techniques to yield information about their morphology and development.