STUDIES ON SKELETON FORMATION IN REPTILES - PATTERNS OF OSSIFICATION IN THE SKELETON OF LACERTA-AGILIS-EXIGUA EICHWALD (REPTILIA, SQUAMATA)

Pattern and sequence of ossification throughout the skeleton of Lacerta agilis exigua Eichwald are described in detail and compared with those of Lacerta vivipara Jacquin. Comparison of timing of ossification allows the identification of skeletal compartments which may shift the timing of onset of ossification relative to each other while preserving the sequence of ossification within each compartment. Pattern (shape and location of appearance) and sequence of ossification may be developmentally correlated with underlying structures such as brain growth and differentiation of the jaw adductor muscle system. The delayed ossification of the dermal skull roof in lepidosaurs is identified as a paedomorphic trait of that group which may have allowed the evolution of mesokinesis in non-fossorial lizards.