Apricardia noncarinata n. sp. (Bivalvia, Requieniidae) from the Cenomanian (Upper Cretaceous) of central-east Sinai, Egypt
Abstract:The new requieniid rudist species Apricardia noncarinata n. sp. is described from the Cenomanian rocks of Wadi Quseib, central-east Sinai, Egypt. The species has been collected from three coral-rudist horizons below the early Late Cenomanian Neolobites vibrayeanus ammonite Zone and therefore has been assigned to the Middle Cenomanian. The new species resembles A. matheroni (Coquand, 1862) from the Upper Turonian of Algeria in having less extended valves, a horizontal commissural plane, and a conical right valve but differs in lacking carinae in any of the valves and in being smaller. As only the outer shape of Coquand's species is known and the internal myophoral structure is an important generic feature in this group of rudist, it may be assigned to any genus of the Requieniidae. The general absence or scarcity of members of the family Requieniidae in the Turonian rocks compared to the Cenomanian is probably due to the widespread marine anoxic event and the global sea-level rise at the Cenomanian-Turonian boundary which drowned previous Requieniidae habitats below their optimum water depth. Also, the extremely thin valves of Requieniidae were probably another important factor in the scarcity of this family during the Cenomanian time. The association of A. noncarinata with other rudists, nerineid and strombid gastropods, and corals indicates a shallow-water carbonate-platform community exposed to medium to high water-energy regimes.
Document Type: Research Article
Publication date: January 1, 2012
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