The ontogeny of supraneurals and neural arches in the cypriniform Weberian Apparatus (Teleostei: Ostariophysi)

A study of nine cyprinid and six catostomid species focused on the early ontogeny of supraneurals and neural arches of the Wehcrian apparatus. These elements chondrify during the mesolarval stage, and there is strong temporal correlation with chondrification of the dorsal-fin pterygiophores. Supraneurals 2 and 3 form from separate chondrification centers that subsequently coalesce. In some cyprinids and catostomids, Sn 2 is at first bilaterally paired. This observation demonstrates that supraneurals are not always unpaired, and provides circumstantial evidence that the paired claustra are homologous to Sn l. Claustra in 14 of 15 species examined possessed at least a cartilage rudiment. No evidence was found to support the currently prevalent hypothesis that the claustra form from dissociated parts of the first neural arch.