Variation in the formation of crista sellaris and basisphenoid in the skull of the grass snake Natrix natrix embryos (Serpentes, Colubridae)

摘要: The crista sellaris is one of the basic structures snake chondrocranium. In embryogenesis it ossifies, forming basisphenoid. This article describes variations sellaris, which, in turn, leads to variation formation basisphenoid skull grass Natrix natrix (Serpentes, Colubridae) embryos. Several embryos at different developmental stages are investigated. Embryos from stage taken simultaneously clutch. Thus, and discovered, including those several embryos, absent or partially formed. absence does not preclude Based on observed may have a origin. with formed develops as complex endochondral bone three ossification centers (paired-in polar cartilages unpaired sellaris). without fully paired mixed origin: appears cartilages, but where absent, by dermal ossification. general, we 15% studied We assume that be due reduction orbital-temporal region chondrocranium N. RESEARCH HIGHLIGHTS: revealed. Depending presence chondral