Hyotissocameleo, a new Cretaceous oyster subgenus and its shell microstructure, from Wadi Tarfa, Eastern Desert of Egypt

Abstract

On the basis of rib morphology and other characters, Ostrea tissoti Peron and Thomas found in Egyptian Campanian sediments is placed in the genus Cameleolopha Vyalov, 1936 and the subgenus Hyotissocameleo n. subgen. This new subgenus is distinguished from Cameleolopha s. s. in having dichotomous to trichotomous round-crested radial ribs, chomata, a long triangular resilifer and a reniform to comma-shaped adductor muscle scar. The main part of the shell shows regularly foliated and in part cross-foliated structure. Neither chalky deposits nor chambers are recorded. Silicification of the original calcitic structure is recognized. Recrystallization and dolomitization resulting from diagenetic processes are observed.