令人大开眼界的发现：5.18亿年前无颌鱼或拥有四只眼睛

Palaeontology An eye-opening discovery Extraordinary fossils of 518-million-year-old jawless fish appear to show that these animals had two pairs of eyes, discovers James Woodford OVER half a billion years ago, the world’s oldest known vertebrates seem to have sported an extra set of eyes – and humans may still carry a remnant of this ancient evolutionary innovation. The team believes this ancient, extra pair of eyes evolved into a set of organs known as the pineal complex. Some vertebrates such as reptiles still have a light- sensitive organ at the top of the head called the parietal eye, but in mammals, the complex consists of only the pineal gland, which regulates our sleep cycle by secreting melatonin. …