Stethacanthus resembled modern sharks to an extent, except for its outrageous dorsal fin - the shape of an ironing board - that it seems was part of courtship display as it is found in the males only.

• 胸脊鲨在大小上与现代鲨鱼类似，除了它不可思议的背鳍--呈烫衣板的形状--只在雄性身上发现，也有可能是求爱中可以炫耀的一部分。