Not to be confused with the Rabbitfish, a group of brightly-colored reef-dwellers.
The rat fish is one of the few fish of the order Chimaeriformes that you can see in person. Though a member of an order that dwells up to 2600 meters (8500 feet) below the surface of the ocean, they are capable of living at surface-level relatively easily, and as such are one of the only Chimaeridae (also known as ghost sharks or ghost fish) that are kept in public aquariums.
Chimaera are the closest living relatives to sharks, though they diverged over 400 million years ago. We have abundant fossil evidence of their evolution to their current forms, and they’re one of the most-studied orders of cartilaginous fish. These fish are the only vertebrates to retain vestigial evidence of a third set of limbs.
Illustrations de Ichtyologie ou histoire naturelle générale et particulière des Poissons. Marcus Elieser Bloch et al., 1795.