Witchellia cf. W. nodatipinguis (Buckman, 1923) [M] (Figs 9K; 10A)

cf. Stiphromorphites nodatipinguis Buckman, 1923: T.A. 4, pl. 398 (HT).

Sonninia cf. S. nodatipinguis – Imlay 1973: 62, pl. 13, figs 1-4.

cf. S. (Euhoploceras) nodatipinguis – Chandler & Whicher 2015: pl. 9, fig. 1.

MATERIAL EXAMINED. — JAC11.3.3 to JAC11.3.8, JAC11. R.9, JAC11. R.43, JAC11. R.44, JAC11. R.45 and JAC11. R.48 to JAC11. R.53.

MEASUREMENTS. — See Table 11.

DESCRIPTION

Small to medium-sized shells, platycone with relatively involute coiling (U/D varying between 0.25 and 0.34). The whorl section is ovate (inner whorls) to almost rectangular, with a vertical umbilical wall, slightly convex flanks, and a tabulate venter with a low keel. The peristome is not present in the available specimens. The innermost whorls appear to have small tubercles, later periumbilical tuberculiform thickenings or primary ribs appear, from which two secondary ribs emerge, one more prominent than the other and, in addition, some weak intercalate ribs appear. On the outer whorls the thickenings progressively disappear, and distinct and less distinct radial ribs alternate, all weakening at the upper half of the flanks, where they gently bend forward and progressively erase, leaving a smooth ventrolateral shoulder near the keel. In some of the smaller specimens (maybe microconchs) the ribs are replaced by striae in the BC. The septal suture is not well preserved but appears to be quite simple.

REMARKS

The specimens described resemble “ Stiphromorphites ” nodatipinguis Buckman, 1923 (Buckman 1923, T.A. 4: pl. 398), but the Subbetic specimens are more involute than the HT of “ St. ” nodatipinguis and have different ornamentation on the inner whorls, and the two species occupy different stratigraphic ranges. Thus while “ St. ” nodatipinguis ” constitutes a characteristic horizon (Bj-8a) in the Trigonalis Subzone of the Laeviuscula Zone (Chandler et al. 2006; Dietze et al. 2008, 2009, 2010a), the Subbetic forms are from the Ovale Zone or even the uppermost Discites Zone.

According to Dietze et al. (2005: 25), this “species” is a small adult form synonymous with S. (Euhoploceras) adicra (Waagen, 1867), but this could not be corroborated because actually S. (Euhoploceras) adicra has an ovate rather than rectangular whorl section on outer whorls and a well developed tuberculate stage that is not present on W. nodatipinguis. Some strongly ribbed Witchellia species such as W. sutneri (Branco, 1879) (HT refigured in Schlegelmilch 1985: pl. 19, fig. 4), W. glauca Buckman, 1925 (Buckman 1925, T.A. 6: pl. 594), W. platymorpha Buckman, 1926 (Buckman 1926, T.A. 6: pl. 580A), W. falcata Buckman, 1926 (Buckman 1926, T.A. 6: pl. 688), and W. actinophora Buckman, 1926 (Buckman 1926, T.A. 6: pl. 689) also bear similarities with the Subbetic specimens in whorl section, coiling, and septal suture, but the four Buckman’ species have sigmoid rather than radial ribbing as well as a different stratigraphic position. The type of W. sutneri has well differentiated ventral sulci and a clear separation between the primary and secondary ribs. The relatively simple septal suture, the tabulate venter, and the absence of well-marked tubercles of the Subbetic specimens makes it closer to Witchellia than to S. (Euhoploceras).

DISTRIBUTION

In the section at Redhole Lane, described byBuckman (1893), Parsons (1974), and Huxtable (2000), the critical interval lies in the so-called Blue Bed, bed 3. There, the upper part, 3b in the section as described by Huxtable, constitutes the type horizon of ‘ Stiphromorphites ’ (Euhoploceras) nodatipinguis Buckman, Horizon Bj-8a, Laeviuscula Zone, Trigonalis Subzone (see Dietze et al. 2005: 76). The specimen figured by Chandler & Whicher (2015) comes from the same faunal horizon. The highly similar specimens, from Oregon (United States), described and figured by Imlay (1973) are also from the Trigonalis Subzone. All the Subbetic specimens appear to be stratigraphically older (lowermost part of the Trigonalis Subzone?, Ovale Zone or even the upper part of the Discites Zone) than any of the strongly ribbed species of Witchellia.