Early development of the chondrocranium in Chrysichthys auratus

The inception and development of the cartilaginous cephalis skeleton of Chr ysichthys auratus is described from hatching to about 18 days post-hatching . At hatching, no skeletal structure is present. Not until day 3 do clearly delimited cranial primordia become apparent. As in many siluriforms, the n eurocranium is platybasic from the start, the suspensorium constitutes, wit h Meckel's cartilage and the hyoid bar, a single cartilaginous element, and the junction between the front and rear of the neurocranium is complete on day 4. By day 8 the quadratomandibular joint has formed and the tectum pos terius has appeared. Cartilage reduction first affects the trabecular bars, then, markedly, the visceral arches. By day Is the braincase floor has alm ost disappeared. (C) 1999 The Fisheries Society of the British Isles.