All the fins have a rounded outline; the short dorsal fin is without a spine, but the males possess a very thick and flattened outer ray in the ventral fins.
The fins of Pteropods are now interpreted as the expanded lateral margins of the foot, termed parapodia, not homologous with the siphonof Cephalopods which is formed from epipodia.
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Latino Coelho, Historia de Portugal desde os fins do XVIII.
These fins contain numerous (15-17) rays, a feature in which the fish differs from the Acanthopterygians.