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How were ganoid scales joined together in palaeonisciform fishes?
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chondrostean
Russian sturgeon (Acipenser gueldenstaedtii) swimming along the seafloor of the Black Sea.
In palaeonisciform fishes, ganoid scales were joined together by a peg-and-socket joint.1
This mechanism involved processes on the anterior end of a scale that fit into corresponding depressions on the posterior end of the scale immediately in front of it. These rhomboidal, enameloid-covered scales provided a protective, interlocking armor characteristic of these early ray-finned fishes.213