In place of eyes, the fish of this genus have large, flattened pale "plaques" on their face which sense light! One study found that larvae of these species have normal lens-having eyes, and so theorised that the developing fish go through a metamorphosis where their eyes become the plaques of adults.
"Nautiluses are a living link to the ancient past.
They’ve been around over 480 million years, cruising deep ocean reefs even before the time of dinosaurs. These soft-bodied creatures live inside an intricately chambered shell.
A nautilus can only sense dark and light with its simple, pinhole-type eyes. But a nautilus can perceive water depth and current directions, as well as current speeds, to help it keep its body upright. A highly developed sense of smell helps a nautilus search for food and find mates."
Full article
- Monterey Bay Aquarium