SEXUAL DIMORPHISM IN THE ALLIGATOR LIZARD GERRHONOTUS INFERNALIS (SAURIA: ANGUIDAE): IMPLICATIONS FOR SEXUAL SELECTION

Sexual dimorphism is common in many clades of reptiles. The Texas alligator lizard (Gerrhonotus infernalis) is a lizard distributed in North America, from Texas in the southern United States to the state of San Luis Potosi in central Mexico. Very little data exist on the presence of sexual dimorphism and on the ecology of this species, particularly in Mexico. We document sexual dimorphism in a population of Gerrhonotus infernalis at Parque Ecologico Chipinque, Monterrey, Nuevo Leon, Mexico. We evaluated 12 morphological and one meristic character on 102 specimens. There were significant differences in the dimensions of the head and body, showing that there is sexual dimorphism in G. infernalis. Males showed positive allometry in cranial dimensions, while females showed isometric growth. Males had more bite marks, suggesting agonistic behavior in this species. This population of G. infernalis presents sexual dimorphism in body size and dimensions of the head, and this is likely a consequence of intrasexual selection.