Development of The Skull of Megalobrama skolkovii and It's Adaptive Signification (Teleostel,Cyprinidae)

The development of skull of Megalobrama skolkovii was divided into five phases:1) Cartilage phase.2) The dermal bones in splanchnocranium phase.3) The beginning of ossification in neurocranium phase.The fast ossification in neurocranium phase.5) The perfect ossification phase.Before the larve hatched,there are no cartilages.When the larva has just hatched,trabuculae,parachordal cartilages,Meckels cartilages,palatoquadrate cartilages,hyosymplectic cartilages,ceratohyal cartilages and the 1st-3nd ceratobranchial cartilages are all present.Then the cartilagious floor of the neurocranium develops.Maxillae and opercles are the first-two dermal bones of the skull,then are premaxillae and dentaries.The first-two bones of the neurocranium are basioccipital and exoccipitals,then is parasphenoid,frontals and parietals appear after the ossification of prootics and vomer.At the same time,most of the splanchnocranium bones are existent,including ectopterygoid,mesopterygoid,metapterygoid,preopercles,infraopercles,interopercles and branchiostegal rays.Then,orbitosphenoids,alisphenoids,sphenotics,epiotics and pterotics all begin ossification.The splanchnocranium has developed well when the fry is 50-55 mm in total length,the neurocranium has developed well when the fry is 70-77 mm in total length.The relationship between the early cartilages and bones with the mechanical demands of biological function such as breething and feeding has been discussed.