Specimens of Contortithyris thermae nov. sp. from the Marnes à Micraster Formation, Early Santonian, Rennes-les-Bains (Aude, France). A–C. Juvenile specimen MNHN.F.A70586 with a rectimarginate anterior margin slightly distorted. D–F. Sub-adult specimen MNHN.F.A70587 with a beginning asymmetrical anterior margin. G–I. Young adult specimen MNHN.F.A70639 with an increasing asymmetry of the anterior margin. J–L. Adult specimen MNHN.F.A70640, with a pronounced left asymmetry (left side down) of the anterior margin. M–O. Adult specimen MNHN.F.A70641 with a pronounced right asymmetry (right side down) of the anterior margin. P–R. Adult specimen MNHN.F.A68144 with a worn posterior shell revealing traces of the dental plates (d. pl.) and dorsal septum (s) in a close-up view (R). Scale bars = 5 mm. Photographs: P. Loubry.