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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The Heritage Group is composed of about 7,500 m of sedimentary strata exposed in the Heritage Range of the Ellsworth Mountains, West Antarctica. The Heritage Group is here redefined to include the Minaret Formation as the uppermost unit. New formations within the Heritage Group are formally described; they are, from the bottom upward, the Union Glacier, Hyde Glacier, Drake Icefall, Conglomerate Ridge, Springer Peak, Liberty Hills, and Frazier Ridge Formations. The Kosco Peak Member of the Union Glacier Formation is also formally described.Deposition of the Heritage Group took place in Middle and early Late Cambrian time in a rapidly subsiding basin bordered by carbonate rock and quartzite source areas of moderate relief. Sediment transport directions were dominantly from the present south and west. Thick, volcaniclastic terrestrial strata lie at the exposed base of the group, and these rocks grade upward into deltaic black shale and normal marine sediments. A number of active volcanic centers were present in the Heritage Range during the deposition of upper Heritage Group strata.

The stratigraphie succession in the Ellsworth Mountains includes strata from Cambrian to Permian in age. No definite evidence of major unconformities in the Ellsworth succession is known, and it is possible that continuous deposition took place from Cambrian to Permian time.The oldest stratigraphie unit, the Heritage Group, was deposited in Middle to Late Cambrian time. More than half of the 13,000+-m-thick stratigraphie succession of the Ellsworth Mountains was deposited during this time interval. Basic igneous volcanism and tectonic activity occurred in both the source and accumulation areas throughout the deposition of this group. Shallow-marine conditions prevailed during the deposition of the overlying 3,000-m-thick Upper Cambrian to Devonian Crashsite Group. This group indicates a period of tectonic stability that continued through the remainder of Ellsworth Mountains sedimentation. Deposition of the glaciomarine Permo-Carboniferous Whiteout Conglomerate and the Permian Polarstar Formation completed the sedimentary sequence. Major deformation of the Ellsworth Mountains sedimentary succession, the Ellsworth (Gondwanide) Orogeny, took place in Late Permian or early Mesozoic time. The original location of these rocks is unclear, but they probably accumulated near the margin of East Antarctica. With the breakup of Gondwanaland, the Ellsworth Mountains, and their southern neighbors likely comprised a microplate that translated and rotated to its present position sometime in late Mesozoic or early Cenozoic time. The uplift of the mountains may have accompanied these postulated movements. The geomorphic evolution of the Ellsworth Mountains in Cretaceous and Cenozoic time includes the development of an integrated stream valley pattern and, later, valley and continental glaciation, followed by moderate déglaciation.