Fig. 9A–B
ITALY – Emilia-Romagna • 1 spec.; Castiglione dei Pepoli; MGGC 22311 (H = 12 mm).
Small, well-inflated, smooth, rounded-pentagonal shell, about as long as high, umbones elevated, blunt, slightly prosogyrate; posterior sulcus close to posterodorsal margin, deep, bordered distinct, roundtopped ridge; submarginal sulcus narrow; anterodorsal margin slightly concave
The two species of Thyasira reported here are all small, poorly preserved, and represented by a single specimen each, making a robust identification difficult. They are placed in Thyasira due to their overall shape and size, and the presence of a shallow posterior sinus. Furthermore, Thyasira sp. 1 appears to have a submarginal sulcus. The two specimens differ in inflation and outline: Thyasira sp. 1 from Castiglione dei Pepoli is more globular than Thyasira sp. 2 from Casola; the latter is taller (it has a longer anterior margin) than Thyasira sp. 1.
Lower to Middle Miocene (Aquitanian to Langhian), northern Italy.