Fig. 8

Erymnaria sp. 1. A Transverse sections (ventral valve up): section 2.05 mm at the plane of articulation shows the rounded teeth with their dental lamellae in the ventral valve, and the large dental sockets marked by the hinge plates in the dorsal valve. Sections 2.2 mm and 2.65 show the sigmoid-like septiform crura in the dorsal valve, in section 2.2 mm the persistent dental lamellae in the ventral valve. B Transverse section (ventral valve up) at the plane of articulation with fused hinge plates, on the right a prominent tooth with dental lamella, loosely inserted in the socket. C (like B): transverse section anterior to the plane of articulation shows separated hinge plates forming the supporting plates, characteristic for the septiform crura type. D Transverse sections, 2.1–2.65 mm of an almost complete series (ventral valve up), showing the persistent parallel dental lamellae in the ventral valve, and the developing crura. The stage of crural development, when becoming detached from the valve floor, could not be observed