An Integrative View of Lepidosaur Cranial Anatomy, Development, and Diversification

Abstract

There are over 10,300 recognized reptile species in the lineage Lepidosauria whose members utilize almost every mode of locomotion except powered flight. They exhibit a diverse array of feeding mechanisms such as the ballistic tongue projection and retraction system of chameleons to the snake macrostomate mode of eating prey larger than their body width. Lepidosauria also exhibit specialized cranial ornamentation and diverse cranioskeletal architecture. The diversity across over 10,300 species makes it unfeasible to conduct an exhaustive review in a short chapter. Herein, we focus our efforts on four phylogenetically, sensory, and phenotypically divergent taxa, the tuatara (Rhynchocephalia: Sphenodon punctatus) and three squamate reptiles: the desert grassland whiptail lizard (Teiidae: Aspidoscelis uniparens), veiled chameleon (Chamaeleonidae: Chamaeleo calyptratus), and the African house snake (Boaedon fuliginosus). While chondro- and osteocranial architecture, cranial muscle, and cranial nerves have been described for various taxa, most reports focus on different taxa but do not provide a description of all three of these tissues for the same species. Herein we present an integrative view of tissue differentiation of the cranium for the latter three species and also develop a reference for future comparative study of the squamate cranium. In addition, we briefly discuss topics as varied as the role of the embryonic cranial base in shaping the adult postorbital skull and the homology of some skeletal elements and jaw adductor musculature as well as the conservation of cranial nerves across Lepidosauria