Final answer:
A key distinction between Gonorhynchiformes and Otophysi is the presence of an operculum covering the gills in Otophysi.
Step-by-step explanation:
A key distinction between Gonorhynchiformes and Otophysi in terms of their anatomical features is the presence of an operculum covering the gills in Otophysi, while Gonorhynchiformes do not have this feature.
The operculum is a protective, muscular flap that allows bony fishes to breathe without having to swim. It covers and ventilates the gills, which are used for respiration. This anatomical difference plays a role in the respiratory system of these two groups of fish.
While both Gonorhynchiformes and Otophysi have other anatomical features like the presence of fins, the operculum is the key distinguishing feature between them.