Craniogenesis in the laughing gull (Larus ridibundus L.). The reconstruction of the basic plan of the bird

To contribute to the knowledge of the cranium of older bird embryos, the chondrocranium and osteocranium of the Black-headed Gull (Larus ridibundus) are described. The chondrocranium of the Black-headed Gull is compared with the chondrocranium of other bird species with special consideration of functional and phylogenetic aspects. As a result a "grundplan" of the bird chondrocranium is reconstructed. Most of the chondrocranial autapomorphies of birds are connected with the enlargement of the eyes, the development of a beak and a prokinetic skull, and the reduction of the olfactory system.