Structure and development of the Weberian ossicles in Heteropneustes fossilis

Mookerjee, H. K.; Ganguly, D. N.; Brahma, S. K.

Previous explanations of the origin of claustrum, scaphium, intercalarium and tripus, and fates of the first several vertebrae in Ostariophysine embryos are reviewed. New explanations are offered on the basis of sections of stages of Heteropneustes. The first vertebra is very small and fused to the second. A modified occipital arch furnishes a perineural tube surrounding the anterior spinal cord. Claustrum and true intercalarium are absent. Scaphium is the modified neural arch of the first vertebra. Tripus is formed by fusion of the 2d and 3d pleural ribs with neighboring fibrous tissue. The whole tripus and part of the scaphium are enclosed within an osseous funnel or air tube formed by fusion of first 4 dorsal ribs with ossified fibrous tissue of the inter-ossicular ligament and the air bladder capsule. The ossa suspensoria are considered to have formed from the basiventral but not to be homolgous with either paraphysis nor haemapophysis.