Patterns of morphological evolution in the raptorial appendages of praying mantises

Mantodea (praying mantises) is a group of exclusively predatory insects, which, together with nonraptorial blattodeans (cockroaches and termites) and groups exclusively found in the fossil record, form the group Dictyoptera. A central characteristic of Mantodea is the specialization of their first pair of legs as raptorial grasping appendages, but the evolution from walking to raptorial legs is not yet fully understood. Here, we trace the evolution of the raptorial appendages in Dictyoptera through time using a morphometric (morphospaces) approach. We also describe two new mantodean nymphs preserved in amber from the Cretaceous and Eocene, which expand the scarce mantodean fossil record. Blattodean and mantodean appendages appear distinct in morphospace, but several appendages of fossil non-mantodeans can be considered raptorial, providing a potential transitional link between walking and raptorial morphotypes. Therefore, we discuss potential mantodean affinities for other predatory fossil dictyopterans. We examine changes across extant mantodeans, characterized by a straightening of the tibia especially associated with the rise of the diversification of the Mantidea and discuss whether a thickening of the femur could reflect an early adaptation to cursorial hunting.