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

Ellis L. Yochelson·Rousseau H. Flower·Gerald F. Webers
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Abstract

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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Ellis L. Yochelson, Rousseau H. Flower, Gerald F. Webers. 1973. The bearing of the new Late Cambrian monoplacophoran genus Knightoconus upon the origin of the Cephalopoda. https://doi.org/10.1111/j.1502-3931.1973.tb01199.x

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