Parasphenoid

The parasphenoid ( Os parasphenoidale , size : para - = next to, sphenoeides = wedge-shaped), is an unpaired cover bone in the skull base of vertebrates . In mammals it has entered the sphenoid bone (os sphenoidale).

Initially sets the basisphenoid as a substitute bone, the notochord and the spinal column in the skull base to the front (in the region of the pituitary gland ) continues. Ventrally, a tooth-bearing cover bone arises in the pharyngeal mucosa: the parasphenoid, which is continued into the tip of the body by the also toothed, short vomer (e.g. still in primitive teleostei such as the osteoglossiformes . Later, the dentition is lost again - as impractical) . The basic phenoid is literally displaced by the parasphenoid and becomes smaller and smaller, in some fish it is already missing. In mammals, both are fused together (mixed bones, called parabasals ) - taking up the paired pterosphenoid of the fish (the " sphenoid wing ").

swell

• Lexicon of Biology. Volume 6. S. 304. Herder Verlag, Freiburg im Breisgau 1985, ISBN 3-451-19646-8
• Ihle, van Kampen, Nierstrasz and Verluys (1927): Comparative anatomy of vertebrates.