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What body shape did most palaeonisciform fishes have?
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chondrostean
Russian sturgeon (Acipenser gueldenstaedtii) swimming along the seafloor of the Black Sea.
Most palaeonisciform fishes were characterized by a fusiform body shape, meaning they were tapered at both ends.1
While this was the standard form, there were notable exceptions:
* Some groups, such as the platysomids and amphicentrids, evolved deep, compressed bodies.1
* A few, such as the tarrasiids, possessed eel-like bodies.1
In addition to their tapered shape, these fishes typically featured blunt snouts, eyes positioned far forward, and bodies covered in rhomboidal (diamond-shaped) ganoid scales.1