Polysacos
Polysacos is an extinct genus of multiplacophorans (chitons) known from articulated Carboniferous fossils; its seventeen shell plates are arranged in three rows, with seven iterated units. It demonstrates that multiplacophora are related to modern polyplacophora.[1] It was fringed with a ring of hollow spines resembling those of the Ordovician Echinochiton.[1] References
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