Plectognath and Sunfish

Plectognath noun - Tropical marine fishes having the teeth fused into a beak and thick skin covered with bony plates or spines.

Sunfish and plectognath are semantically related. In some cases you can replace term "Sunfish" with "Plectognath", this nouns are similar.

Sunfish noun - Among the largest bony fish; pelagic fish having an oval compressed body with high dorsal and anal fins and caudal fin reduced to a rudder-like lobe; worldwide in warm waters.

Plectognath and sunfish are semantically related. Sometimes you can use "Plectognath" instead a noun "Sunfish".