The Bittium−like cerithiid ?Cryptaulax mutabilis (Gerasimov, 1955) from the Late Callovian (Mid Jurassic) of Łuków (block in glacial drift); specimen ZPAL Ga.9/168 in lateral and apical view.

Diagnoza

Small shell, Bittium-like, of about 11 nearly flat whorls. Suture weakly incised. Teleoconch ornamentation with axial (12–13 per whorl) and 4–5 spiral ribs. At the intersections, blunt nodes appearing. In early ontogeny, axial ribs stronger than spiral ribs and later both of similar dimensions. Peristome drop-like with weak siphonal canal.

Porównanie

The early whorls of the teleoconch are typical of the genus Cryptaulax. Later whorls are more similar to the extant Bittium-like gastropods and differ significantly from the other known members of the genus Cryptaulax in having nearly flat whorl flanks and weakly incised suture.

Autekologia

Występowanie geograficzne

Lithuania, Russia and Ukraine; in Poland found only in Łuków (block in glacial drift).

Zasięg czasowy

Callovian (Mid Jurassic); In Poland Late Callovian

Materiały muzealne

One incomplete shell from Łuków.

Literatura

Gerasimov,  P.A. 1955. Pуководящие ископаемые мезозоя Центральных областей Европейской части СССР. Часть 1. Пластинчатожаберные, брюхоногие, ладьеногие моллюски и плеченогие юрских отложений. 379 с. М., Госгеолтехиздат, Moscow

Gerasimov, P.A. 1992. Gastropody yurskih i pogranichnyh nizhniemielovyh otlozhenii evropeiskoi Rossii. 190 pp. Nauka; Moskva.

Kaim, A. 2004. The evolution of conch ontogeny in Mesozoic open sea gastropods. Palaeontologia Polonica 62, 3–183.

Riabinin, V.N.  1912. Gastropods from the Jurassic strata of Popelyany and Nigranden (Lithuania and Kurlyandiya). Zapiski St.-Peterburgskogo Mineralogicheskogo 0bshchestva, Ser. 2 48, 231–269.