Stylophorans in middle Arenig shallow water siliciclastics: Vizcainocarpus from the Imfout Syncline in Morocco's western Meseta


Authors: Parsley RL, Gutiérrez-Marco JC

Published in: Bulletin of Geosciences, volume 80, issue 3; pages: 185 - 192; Received 25 November 2004; Accepted in revised form 13 April 2005;

Keywords: Echinodermata, stylophorans, Vizcainocarpus, middle Arenig, Imfout Syncline, Morocco,

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Numerous specimens of the ankyroid Vizcainocarpus naimae sp. nov. (Stylophora, Echinodermata) have been found in middle Arenigian shallow-water, inner shelf, fine to medium grained siliciclastics of the Oum-er-Rbia Formation, located in the Imfout Syncline in Morocco's western Meseta. Their occurrence in this sedimentary/ecological setting is atypical because ankyroids are most common in deeper water calcisiltites and limestones. Aspects of orientation and feeding habits in the debate over stylophorans as echinoderms or calcichordates (ongoing since the 1960s) appear to be largely resolved by data derived from these specimens. The aulacophores of most specimens face into the prevailing sediment-depositing current and appear to have draped over the adjacent sand wave. There is no evidence that they were orientated in the calcichordate mode with the convex side of the theca facing down and aulacophore extending into the substrate, as proposed by Jefferies (1973, 1986, 2001) and Sutcliffe et al. (2000).