Pleuronautilus
Pleuronautilus is a nautiloid genus; family Tainoceratidae, order Nautilida.[1] DescriptionThe shell is evolute, discoidal; whorl section subquadrade, flanks generally straight but may converge toward the venter. Inner flanks have course ribbing, outer have rows of nodes. Sutures have shallow ventral, lateral, and dorsal lobes. Its siphuncle is small and approximately central. Fossil recordsPleuronautilus has been found in Upper Permian marine limestone in Armenia, China, and Iran, sometimes associated with orthocerids, ammonoids, and other nautilids as well as other invertebrates; in Upper Permian offshore mudstone and calcareous siltstone in the northern Caucasus, and in upper Lower Permian marine sediments in Tajikistan with grypoceratids and pronoritids. It has been found also in Lower Triassic black marine calcareous shale in Afghanistan with orthocerid, aulacocerid, phylloceratitd and ceratitid cephalopod genera and in early Upper deltaic shale and marl with ceratitids, pelecypods, and gastropods in Slovenia; and mid upper offshore mustone with Paranautilus and Rhacophyllites and ceratitids in western Nevada.[1] SpeciesSpecies within this genus include:[1]
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