And it might've been pressure to find a new feeding niche that drove this switch from face-up to face-down, since the Ordovician witnessed an explosion in suspension-feeding, with lots of competition for floating bits of food.

并且可能是寻找新的喂养生态位推动这种从面朝上到面朝下的转变的压力，因为奥陶纪见证了悬浮喂养的爆炸式增长，对漂浮的食物进行了激烈的竞争。