Crommium acutum ( Lamarck, 1804 )

Caze, Bruno, Merle, Didier, Meur, Mathieu Le, Pacaud, Jean-Michel, Ledon, Daniel & Martin, Jean-Paul Saint, 2011, Taxonomic implications of the residual colour patterns of ampullinid gastropods and their contribution to the discrimination from naticids, Acta Palaeontologica Polonica 56 (2), pp. 329-347 : 338

Crommium acutum ( Lamarck, 1804)

Fig. 6A–C .

Stratigraphic and geographic range.—Middle Eocene, Lutetian–Bartonian (PB, HB)

Colour pattern description.—The shells show three levels of residual colouration. The background is heterogeneous with a fluorescent area covering the apical part of the whorl ( Fig. 6A, B ) (except a thin zone just below the suture). The apex is pale. The transition between the two levels of colouration of the background is diffuse. There is sometimes a second fluorescent diffuse area on the base of the shell. These fluorescent areas cover a smaller or larger part of the whorl. The largest specimens show an entirely fluorescent last whorl (except the subsutural part). The young specimens display three or four thin spiral fluorescent stripes: one on the shoul− der, one on the base (but often lacking) and two on the median part of the whorl ( Fig. 6C ). The two median stripes fade with growth until they disappear. The adapical one and the basal one, when present, gradually spread on the whorl.

Figures

Fig. 6. Species of the genus Crommium Cossmann, 1888, under UV light. A. Crommium acutum (d’Orbigny, 1850), MNHN B58618 (MNHN coll.), Parnes, Oise, France, Lutetian, in ventral view. B. Crommium acutum (d’Orbigny, 1850), MNHN A30889 (MNHN coll.), Boursault, Marne, France, Lutetian, in ventral view. C. Crommium acutum (d’Orbigny, 1850), MNHN A30861 (MNHN coll.), Fleury−la−rivière, Marne, France, Lutetian, in ventral (C1) and dorsal (C2) views. D. Crommium grignonensis (d’Orbigny, 1850), type of Natica heberti Deshayes, 1864, MNHN J04185 (Hébert coll.), Chaumont−en−Vexin, Oise, France, Lutetian, in ventral view. Scale bars 10 mm. Photographs by C. Lemzaouda and P. Loubry (MNHN).