ISSN:
0362-2525
Schlagwort(e):
Life and Medical Sciences
;
Cell & Developmental Biology
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Biologie
,
Medizin
Notizen:
The development of the chondrocranium of the Egyptian snake, Psammophis sibilans has been thoroughly studied in six developmental stages. The neurocranium and viscerocranium develop at the same time. In early stages the mesocephalic flexure is well represented, but later it is gradually reduced. The notochord is completely embedded inside the parachordal plate in the early and moderate stages, and the paired origin of the plate is not observed. From the very beginning the quadrate cartilage is in close contact with Meckel's cartilage. In early stages the two cartilages lie nearly at the same straight line, and throughout development the quadrate rotates freely until the angle between it and Meckel's cartilage becomes nearly a right one. It was impossible to find a stage at which the auditory capsules and their cochlear portions were separate from the parachordal plate. There is no interorbital septum and the platytrabic character of the chondrocranium is preserved. The basicranial fenestra, fenestrae X and the fenestra ovalis are formed by the resorption of pre-existing cartilage. The planum antorbitale has no separate center of chondrification. The rudiment of a simplified type of concha nasalis is formed in the last stage. The lamina transversalis anterior is formed of two separate portions. The tectum synoticum is of purely otic origin.
Zusätzliches Material:
25 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/jmor.1051160205
