Calliostoma normanensis, Bouchard & Wesselingh & Pouwer & Landau, 2025

Calliostoma normanensis n. sp.

( Figs 4K View FIG 1-K View FIG 3 View FIG ; 5A View FIG 1-A View FIG 3 View FIG )

urn:lsid:zoobank.org:act:662E6CB4-0935-4328-8183-A0419A765952

TYPE MATERIAL. — Holotype: MNHN.F.A91315 , height 12.8 mm (incomplete), width 14.7 mm, leg. AWJ.

Paratypes: paratype 1, RGM.1365210 , height 8.2, width 8.7 mm (juvenile), leg. WG ; paratype 2, RGM.1365270 , height 12.7 mm (incomplete), width 13.4 mm, leg. WG ; paratype 3, RGM.1364926 , height 9.1 mm (incomplete), width 10.9 mm, leg. ACJ ; paratype 4 RGM.1364963 , height 10.9 mm (incomplete), width 13.7 mm, leg. AWJ .

DIAGNOSIS. — Trochoid shell with broad, evenly conical spire, flattened base, imperforate, spiral sculpture of four finely beaded primary cords with secondary threads intercalated, 13 weakly beaded cords on base, columella strongly oblique.

ETYMOLOGY. — Named after the Region of Normandy in which the type locality is situated.

TYPE LOCALITY. — Selsoif , Saint-Sauveur-le-Vicomte, Manche department, NW France.

STRATUM TYPICUS. — Gelasian, Early Pleistocene.

OTHER MATERIAL EXAMINED. — Maximum height approx. 17 mm (incomplete), width 16.4 mm. — RGM.1364904 (11 juveniles), leg. WG ; RGM.1364970 , (27 juveniles + one incomplete adult), leg. ACJ ; RGM.1365069 (22 incomplete adults and fragments), leg. AWJ .

DISTRIBUTION. — Lower Pleistocene: Atlantic, Selsoif, France (this paper).

DESCRIPTION

Shell medium sized, trochiform; protoconch not preserved; five teleoconch whorls preserved, initially flat-sided, later whorls slightly swollen just above suture, separated by superficial suture; sculpture on first teleoconch whorl of four finely beaded spiral cords; on second whorl, single secondary spiral intercalated between adapical spiral and second primary cord, strengthening abapically to become almost equal in strength to primaries on later adult whorls. On penultimate whorl secondaries appear between the second and third primaries and between the fourth and the suture. Axial sculpture reduce to weak prosocline growth-lines. Last whorl 47% of total height; slightly inflated and strongly rounded at periphery; on last whorl single secondary intercalated in all interspaces, some secondaries almost equal in strength to primaries. Base depressed, imperforate, bearing 13 weakly beaded concentric cords, widening and strengthening toward columella. Aperture subquadrate, 35% of total shell height; outer lip simple, strongly prosocline in profile, roundly angled at base. Columella strongly inclined abaxially, slightly thickened, parietal callus absent.

COMPARISON

The Selsoif material has sculpture similar to that of Calliostoma subexavatum ( Wood, 1848) described from the Upper Pliocene Red Crag of England but differs in being lower spired (although one of the specimens figured by Harmer 1923: pl. 57, fig. 15 is similar in profile to the material at hand), and in not having the abapical cord developed into a well-defined and inflated suprasutural band. In some specimens from Selsoif there is a slight tendency for the abapical cord to form a narrow band, but far less prominent than that seen in the Red Crag specimens, or the ones illustrated by Lauriat-Rage et al. (1989: pl. 8, figs 5, 6) from the Lower Pliocene of La Limouzinière (NW France). Several similar Calliostoma species occur in the Pliocene NSB that share similarities with the Selsoif material. Calliostoma simile (Sowerby, 1818) differs in having only beads on the adapical cord on later adult whorls and has weaker spiral sculpture on the base, that is obsolete in some specimens. Calliostoma multigranus ( Wood, 1848) is probably the most similar with four beaded primary spirals on early whorls, but that species has a narrower apical angle, and a fifth primary appearing at the suture on the second teleoconch whorl, and secondaries are only intercalated on the last whorl. Moreover, the last whorl is less inflated at the periphery, the base is less depressed and there are fewer, smoother concentric cords over the base. Calliostoma noduliferens ( Wood, 1848) differs in having five beaded primary cords per whorl. The modern European Calliostoma zizyphinum ( Linnaeus, 1758) is similar in profile, but the cords tend to become smooth on latter whorls, the abapical cord placed just above the suture is usually strengthened, and cords at the periphery and the base are smooth. Calliostoma conulus ( Linnaeus, 1758) is larger with a narrower apical angle and a taller spire and even smoother sculpture on later teleoconch whorls. Calliostoma granulatum (Born, 1778) is larger shelled with a cyrtoconoid spire, more sharply angled at the base, the cords are more finely beaded, and the abapical cord placed just above the suture is usually strengthened.