Sea gurnard (Chelidonichthys obscurus)
The Triglidae, commonly known as sea robins or gurnard, are a family of bottom-feeding scorpaeniform fish. They get their name (sea robin) from the orange ventral surface of the species in the Western Atlantic (Prionotus carolinus) and from large pectoral fins, which, when swimming, open and close like a bird's wings in flight. The large surface area of the fins also permits the fish to glide short distances above the water surface, much like a flying fish.
They are bottom-dwelling fish, living down to 200 m (660 ft), although they can be found in much shallower water. Most species are around 30 to 40 cm (12 to 16 in) in length. They have an unusually solid skull, and many species also possess armored plates on their bodies. Another distinctive feature is the presence of a "drumming muscle" that makes sounds by beating against the swim bladder. When caught, they make a croaking noise similar to a frog, which has given them the onomatopoeic name gurnard.
Sea robins have six spiny "legs", three on each side. These legs are actually flexible spines that were once part of the pectoral fin. During development, the spines separate from the rest of the fin, developing into feeler-like "forelegs". The pectoral fins have been thought to let the fish "walk" on the bottom, but are really used to explore the bottom in search of food. The first three rays of the pectoral fins are membrane-free and used for chemoreception being highly sensitive to amino acids prevalent in marine invertebrates.