Jeanclaudella variata ( Conti & Fischer, 1981 ), 2025

Jeanclaudella variata ( Conti & Fischer, 1981) new comb.

Fig. 2 View FIGURE 2

v* 1981 Aaleniella variata Conti & Fischer , p. 141, figs 4–6.

v 1984 Aaleniella variata Conti & Fischer , p. 138, pl. 2, figs 13a–c, 14.

v 1994 Aaleniella variata Conti & Monari , p. 199, fig. 1c.

Material. Holotype MPUR MAC19 A, four Paratypes, MPUR MAC19 B-MAC19 E. Case Canepine ( Martani Mountains , Umbria, central Italy), lower Bajocian, Stephanoceras humphriesianum Zone.

Description. The shell is small-sized (max height 3.4 mm; width 2.9 mm) and composed of five whorls. Its shape is rather cyrctoconoidal. The protoconch is prominent and seemingly consists of less than one volution. Its width is about 0.25 mm. The coiling axis of the protoconch is slightly deviated from that of the subsequent whorls and this makes the apex prominent and submamillate. The first three whorls are strongly and evenly convex with the suture well-impressed and incised. They increase rapidly in height after the first teoleoconch whorl. During the growth of the third whorl, the surface of the whorl becomes rapidly concave. It is edged adaxially by a subsutural spiral keel and abaxially by a stronger peripheral keel. These two keels border a groove where the suture runs. The last whorl is 0.69–0.74 of the height of the shell. The base is convex, moderately inflated and narrowly umbilicated. The aperture is rounded-quadrangular. The peristome is discontinuous and provided with a thin parietal inductura. The early teleoconch whorls are ornamented with 20–30 strong and opisthocyrt collabral ribs. The adult part of the shell bears more widely spaced and distinctly prosocline collabral ribs which form roundly pointed nodes on the spiral keels. The collabral ribs become thinner or disappear on the median band of the whorl surface. The base is sculptured by three strong, widely spaced spiral keels separated by concave interspaces. The most abaxial spiral keel is coupled by the peripheral keel and is just covered by the suture. The three spiral keels of the base bear nodes at intersection with low collabral ribs which tend to vanishing in adaxial direction within the interspaces. The growth lines are strongly prosocline and slightly sinuous on the spire, and widely opisthocyrt on the base.

Remarks. The prominent and slightly deviated protoconch, which gives to the apex a submamillated shape, is a notable feature of Jeanclaudella variata ( Conti & Fischer, 1981) . Its size is well-comparable with that of other Mesozoic eucycloideans (e. g., Bandel 2010).

The other species of Jeanclaudella differ from J. variata in the conoidal or less cyrtoconoidal outline of the shell, in the early teleoconch whorls increasing more slowly and more regularly in height during the growth and in the coarser ornament. In J. variata , the collabral ribs of the adult part of the shell are stronger and make more prominent, subpointed nodes both on the subsutural and peripheral keel. Moreover, the base is ornamented only with three, nodose and much stronger spiral keels of which the outermost runs alongside the peripheral keel.

Mistelgauia faustiankensis ( Ferrari & Kaim, 2018) differs from J. variata in characters here considered of genus level i. e., the more globose shape of the shell with inflated base and the ornament of the base. Other differences from J. variata are the conoidal outline of the shell, the blunt apex and the regular increment of the height of the whorls during the growth.