Geckos with armor

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Gekkota-0015.jpgGekkota-0015.jpg

Osteoderms, bones that form in dermal tissue maybe a continuous or patchy layer of hard tissue in the dermis, a trait that is found in many lineages of tetrapods, including frogs, dinosaurs, leatherback turtles, crocodilians, and lizards. The result is armored skin. Osteoderms are uncommon in gekkotans (geckos and flap-footed lizards) and only known to occur in three genera: Geckolepis, Gekko, and Tarentola. In a new paper Laver et al. (2020) report on the armored dermis in the Tokay gecko (Gekko gecko), one of the best-studied geckos due to its large size and large distribution. The cranial dermal bone development was previously investigated, but details of osteoderm development along a size gradient remain less well-known. Similarly, a comparative survey of additional species within the Gekko clade to has not yet been completed. Laver et al. studied a large sample of gekkotans (38 taxa), including 18 specimens of G. gecko, using X-rays and high-resolution computed tomography for visualizing and quantifying the dermal armor in situ. Results from this survey confirm the presence of osteoderms in a second species within this genus, Gekko reevesii, which exhibits discordance in timing and pattern of osteoderm development when compared with its sister taxon, G. gecko. The authors discuss the developmental
sequence of osteoderms in these two species and explore in detail the formation and functionality of these enigmatic dermal ossifications. They also conducted a comparative analysis of endolymphatic sacs in a wide array of gekkotans to explore previous ideas regarding the role of osteoderms as calcium reservoirs. The authors found that G. gecko and other gecko species with osteoderms have greatly enlarged endolymphatic sacs relative to their body size, when compared to species without osteoderms, suggesting that these membranous structures might fulfill a major role of calcium storage even in species with osteoderms.

Laver RJ, Morales CH, Heinicke MP, Gamble T, Longoria K, Bauer AM, Daza JD. The development of cephalic armor in the tokay gecko (Squamata: Gekkonidae: Gekko gecko). Journal of morphology. 2020 Feb;281(2):213-28.

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