Tongue Morphology in Horned Lizards (Phrynosomatidae: Phrynosoma) and its Relationship to Specialized Feeding and Diet

Abstract

In lizards, the tongue is joined to the mandible by the median genioglossus medialis muscle and the larger, paired genioglossus lateralis muscles. These muscles run through a frenulum and along the sides of the tongue, forming its walls. In horned lizards, however, the genioglossus lateralis muscles fail to join the tongue for most of its length, forming separate ridges evident in the floor of the mouth lateral to the body of the tongue. This unique tongue morphology co-occurs with horned lizards’ ability to consume large numbers of potentially lethal harvester ants, a diet enabled by a feeding mechanism in which ants are rapidly immobilized with strings of mucus before immediate swallowing. Circumstantial evidence implicates the unusual morphology of the genioglossus lateralis muscles in the mucus-binding system.