词条 | Plectoceras |
释义 | Plectoceras fossil cephalopod extinct genus of small marine nautiloid cephalopods, forms related to the modern pearly nautilus, that had a coiled shell composed of a series of chambers; Plectoceras was active in the Ordovician Period (from 505 to 438 million years ago). The junctures between successive chambers of Plectoceras were simple in character. |
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