Body size miniaturization in a lineage of colubrid snakes: Implications for cranial anatomy

As body size strongly determines the biology of an organism at all levels, it can be expected that miniaturization comes with substantial structural and functional constraints. Dwarf snakes of the genusEirenisare derived from big, surface-dwelling ancestors, considered to be similar to those of the sister genusDolichophis. To better understand the structural implications of miniaturization on the feeding apparatus inEirenis, the morphology of the cranial musculoskeletal system ofDolichophis schmidtiwas compared with that of the miniatureEirenis punctatolineatusandE. persicususing high-resolution mu CT data. The gape index was compared betweenD. schmidtiand 14Eirenisspecies. Our results show a relatively increased neurocranium size and decreased maximal jaw muscle force inE. persicus, compared with theD. schmidti, and an intermediate situation inE. punctatolineatus. A significant negative allometry in gape index relative to body size is observed across the transition from theDolichophistoPediophisandEirenissubgenera. However, the gape index relative to head size showed a significant negative allometry only across the transition from theDolichophistoPseudocyclophissubgenus. InDolichophis-Eirenisdwarfing lineages, different structural patterns are observed through miniaturization, indicating that overcoming the challenge of miniaturization has achieved via different adaptations