| Summary: | A new naticid gastropod, Euspira? louiemarincovichi n. sp., is described from the Pliocene to Pleistocene age Gubik Formation on the North Slope of Alaska between Skull Cliff in the west and the Kogru River/Teshekpuk Lake area in the east. It is easily distinguished from all other Atlantic, Pacific and Arctic oceans naticids by its fine radial and somewhat stronger spiral ribs. This new species lived during a time when water temperatures were warmer in the Arctic than today based on the occurrence of the gastropod genus Littorina with which this new species co–occurs. As such, Euspira? louiemarincovichi likely lived in the upper intertidal zone on hard substrate and were not present where sea–ice impinges on the shoreline. Based on co–occurrences of extinct species and the temperature regime indicated by Littorina, of significantly warmer temperatures, and some associated species, this new species probably lived during the Bigbendian and (or) Fishcreekian marine transgressions, or between about 2.5 and 2.1 Ma, which is the Gelasian Stage of the early Pleistocene.
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