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How do American soles differ from other soles in their pelvic fins?
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pleuronectiform
Body plan and sexual dimorphism in the common sole (Solea solea) and dusky flounder (Syacium papillosum).
Within the order Pleuronectiformes, American soles (family Achiridae) are distinguished from other soles, such as those in the family Soleidae, by the attachment of their pelvic fins. Specifically, in American soles, the right pelvic fin is attached to the anal fin. In contrast, the pelvic fins of soles in the family Soleidae are free from the anal fin.1