Embryological development and comparative analysis of Anguis colchica (Nordmann, 1840): Insights into ossification and morphological traits in anguimorph lizards

Embryological studies on squamates, dating back to the 19th century, remain limited, particularly concerning species within the anguimorph clade, a group of lizards with distinct morphological traits. In this study, we document the embryological development of Anguis colchica through three stages and provide a comparative analysis with other anguimorph species. Morphological features, including eye formation, pharyngeal arch development, fusion of facial primordia, limb morphogenesis, pigmentation, and scale differentiation characterized developmental stages. The development of A. colchica was analyzed across three embryonic stages, with adult skeletal structures also assessed and compared to those of other anguimorphs. Our findings indicate that ossification in A. colchica begins before stage 6, marked by the emergence of cranial skeletal elements such as the premaxilla, maxilla, nasal, prefrontal, parietal, squamosal, quadrate, mandible, postorbital, and postfrontal bones. At stage 7, the medial regions of the frontal and parietal bones remain unfused. Understanding whether skull and skeletal structure variations influence ossification patterns in anguimorphs is crucial. Comparative analysis of developmental sequences across different anguimorph species reveals significant similarities in their embryological progression.