The bearing of the new Late Cambrian monoplacophoran genus Knightoconus upon the origin of the Cephalopoda

Authors

  • ELLIS L YOCHELSON,

    1. U. S. Geological Survey, Washington, D. C.; R. H. Flomer, New Mexico Bureau of Mines, Socorro, New Mexico; G. F. Webers, Macalester College, St. Paul, Minnesota. 9th May, 1972. [Publication authorized by the Director, U.S. Geological Survey]
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  • ROUSSEAU H. FLOWER,

    1. U. S. Geological Survey, Washington, D. C.; R. H. Flomer, New Mexico Bureau of Mines, Socorro, New Mexico; G. F. Webers, Macalester College, St. Paul, Minnesota. 9th May, 1972. [Publication authorized by the Director, U.S. Geological Survey]
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  • GERALD F. WEBERS

    1. U. S. Geological Survey, Washington, D. C.; R. H. Flomer, New Mexico Bureau of Mines, Socorro, New Mexico; G. F. Webers, Macalester College, St. Paul, Minnesota. 9th May, 1972. [Publication authorized by the Director, U.S. Geological Survey]
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Abstract

Yochelson, E. L., Flower, R. H. & Webers, G. F.: The hearing of the new Late Cambrian monoplacophoran genus Knightoconus upon the origin of the Cephalopoda.

Knightoconus, a new genus of the Hypseloconidae (Mollusca: Monoplacophora) from rocks of early Franconian age in Antarctica, is multiseptate. The multiple septa are a criticàl feature to be expected in a form ancestral to cephalopods. Fossil cephalopods, however, invariably have a siphuncle as well as septa; some gastropods, some hyolithids, and some monoplacophorans also have septa but lack a siphuncle. Therefore, only the siphuncle can be considered a unique and particularly significant feature of the cephalopod shell. Hypothetical reconstructions of molluscan anatomy support the notion that cephalopods may have been derived directly from a hypseloconid having a high, slightly curved, multiseptate, bilaterally symmetrical shell, by the subsequent development of a siphuncle.

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