Queensland State Archives posted a photo:
Artwork by George Coates
There are over 30 species of parrotfish on the Great Barrier Reef, and all share a few common traits. The most obvious of all relates to their teeth. Parrotfish evolved from the carnivorous wrasse family, but through the course of time, their teeth have moved forward on the jawbone and reduced in size. Eventually, the teeth fused together, creating a very useful tool for scratching algae off the surface of the coral.
When parrotfish sleep at night, they often secrete a mucus sleeping bag around themselves to protect themselves from predators. The bags also have antibiotic properties that are beneficial for the fish.
Queensland State Archives, Digital Image ID 5966