Ontogeny and homology of the neural complex of otophysan Ostariophysi

Abstract

The development and homology of the neural complex in the ostariophysan subgroup Otophysi were studied, including for the first time representatives of all four major otophysan lineages. Previous hypotheses concerning the homology of the different elements of the neural complex have also been reviewed and these are discussed in light of our new findings. We found that supradorsal cartilages, paired autogenous elements at the medial side of the neural arches, play a previously unrecognized major role during the ontogeny and evolution of the neural complex. In most otophysan taxa, supradorsals 3 and 4 fuse with supraneurals 2 and 3 (cypriniforms) or supraneural 3 (characiforms, some siluriforms, gymnotiforms) during ontogeny to form the neural complex. In the majority of siluriforms, the neural complex is exclusively formed by supradorsals 3 and 4. In loricarioid siluriforms, a neural complex is missing, the fourth neural arch fuses to the occiput in development, and the first free vertebra is the fifth. Of the four otophysan subgroups, siluriforms are the most and cypriniforms the least diverse in the structure and development of their neural complex. © 2006 The Linnean Society of London.