Early stages of skull embryogenesis in the Grass snake, Natrix natrix (Serpentes, Colubridae)

摘要: Studies of previous authors on snake skull embryogenesis have been performed embryos obtained from eggs after oviposition. The aim this study was to investigate the initial stages chondrocranium development in Grass-snake Natrixnatrix Linnaeus, 1758, before Natrix natrix at early developmental (24-27 according table normal by D. Zehr (1962)) were means caesarean section. At 25-27, previously undescribed structures found region future formation. These exist during one or two and then disappear. Therefore, we call them "temporary structures." assumption about nature these is based their topography comparison with developing fully formed other vertebrates. It hypothesized that temporary are vestiges ofprimary ancestral vertebrate forms, they indicate existence several variants formation historical vertebrates.' development.