Eggs with shells. Fertilization proble ms. A good example of the problem of adaptation is hearing .
Fish hear with something called their lateral line organ.
The Early Cambrian Burgess Shale is one of the rare localities were we see great preservation of soft-bodied forms. Lo w oxygen. Lack of sc avengers. The Burgess Shale contains a beautiful, diverse fauna including Pikaia , the first chordate, and some very odd forms, such as Hallucigenia . Recent discoveries in China and elsewhere indicate that Burgess taxa such as Ayshaia and Hallucigenia were onychophorans.