A transitional stringocephalid from the Holy Cross Mountains, Poland, and its evolutionary and stratigraphic significance

Abstract

Stringocephalini gen. et sp. indet. A shows microscopic capillae on both valves, possibly representing a transitional evolutionary stage between smooth-shelled Stringocephalus and capillate Parastringocephalus. The latter genus seems therefore to have originated directly from Stringocephalus, and not via Subsinucephalus, as suggested earlier. The occurrence of Stringocephalini gen. et sp. indet. A indicates an early Givetian age of beds cropping out at Błonia Sierżawskie near Świętomarz.