Ozarkian and Canadian Cephalopods: Part II: Brevicones
E. O. ULRICH, AUG. F. FOERSTE, A. K. MILLER, 1943. "Ozarkian and Canadian Cephalopods: Part II: Brevicones", Ozarkian and Canadian Cephalopods: Part II: Brevicones, E. O. Ulrich, Aug. F. Foerste, A. K. Miller
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More than half of the known specimens of Ozarkian and Canadian cephalopods are brevicones. They are of widespread occurrence and are locally abundant in the United States, Canada, and Newfoundland. In age they range from Lower Ozarkian to uppermost Canadian, but the bulk of those now at hand come from the Middle and Upper Ozarkian and the Upper Canadian. Comparatively little knowledge is available in regard to related faunas outside of North America, but such occur in both western Europe and eastern Asia.
Most of the known forms axe superficially similar. They vary chiefly in the shape of the conch and the nature of the siphuncle. Primarily on the basis of these features, they have been divided into four families: the Piloceratidae (37 species representing 6 genera), the Cyclostomieeratidae (9 species, 3 genera), the Cyrtendoceratidae (141 species, 13 genera), and the Beekmanoceratidae (1 species, 1 genus). It is perhaps significant that the great majority of our specimens fall readily into one of two groups, the Cyrtendoceratidae, characteristic of the Middle and Upper Ozarkian, and the Piloceratidae, essentially limited to the Upper Canadian.