Witchellia laeviuscula (J. de C. Sowerby, 1824 )

Sandoval, José, 2022, Sonniniidae Ammonitina, Middle Jurassic from Southern Spain: taxonomic, biostratigraphical and palaeobiogeographical analysis, Geodiversitas 44 (27), pp. 801-851 : 832-834

Witchellia laeviuscula (J. de C. Sowerby, 1824) [M] ( Fig. 13C )

Ammonites laeviusculus J. de C. Sowerby, 1824: 73 , pl. 451, figs 1, 2. — Buckman & Woodward 1908: pl. 6, fig. 1 (LT refigured).

Harpoceras laeviusculum – Haug 1885: 682, pl. 12, fig. 6.

Witchellia laeviuscula – Buckman 1927: T.A. 7, pl. 745. — Dorn 1935: 106, pl. 6, fig. 3, pl. 14, fig. 2, pl. 15, fig. 3, text-fig. pl. 9 (4, 5). — Gillet 1937: 61, pl. 1, fig. 8, pl. 2, fig. 6, pl. 3, fig. 1.). — Westermann 1969: 111, fig. 35 (LT refigured). — Schlegelmilch 1985: 63, pl. 19, fig. 3 (LT refigured). — Fernández-López 1985: 70, text-fig. 8A, pl. 7, fig. 2. — Chandler et al. 2006: 351, figs 4.1- 4.3 (LT refigured), 5.1-5.2. — Metodiev 2019: 15, fig. 5a, b.

cf. Witchellia aff. laeviuscula – Morton 1975:18, pl. 10, figs 1, 2.

Witchellia aff. laeviuscula – Chandler et al. 2006: 351, fig. 4 (4).

Witchellia laeviuscula [M] – Dietze et al. 2009: 21, figs 21, 22, 26.

MATERIAL EXAMINED. — JAC3.71.2 , JAC3.72.1 , JAC3.77.1 , Jpe1 , JAC3’.0.5 , JAC3’.4.37 , JAC3’.8.2 , JAC22.56.23 , JAC22.57.4 .

MEASUREMENTS. — See Table 18.

DESCRIPTION

Disc-shaped shells with relatively involute coiling. The compressed whorl section is subtriangular with flanks slightly convex and convergent towards the outer region; the maximum width of the whorl is located near the lower third of the height of the flanks. The umbilicus is moderately narrow and deep. The umbilical wall is flat and nearly vertical, with a slightly rounded umbilical edge and a barely differentiated ventrolateral shoulder; the narrow ventral region which is tabulated in the inner and median whorls. The keel is thin and prominent, without lateral grooves at least in the middle and outer whorls. The ribbing is irregular, with a thick rib followed by two weak, blunt, and widely spaced ribs in the middle whorls, becoming increasingly attenuated and disappearing almost completely throughout ontogeny. The ribs are flexuous and generally bifurcate near the umbilical edge; the primaries are hardly marked, proverse and short whereas the secondaries, divided from the primaries near the umbilical edge, project strongly forward in the ventral region. In the HT, the internal whorls, somewhat more evolute than the intermediate ones, have dilated primary ribs next to the umbilical edge. The septal suture, relatively simple, with a wide and short L in the HT, is poorly preserved in the Subbetic specimens.

REMARKS

Subbetic specimens are slightly more evolute than the HT, but they coincide with it in the other characters. Callomon & Chandler in Chandler et al. (2006: 370) point out that several relatively involute forms of Witchellia as W. laeviuscula ( Sowerby, 1824) , W. actinophora Buckman, 1926 , W. falcata Buckman, 1926 , W. glauca Buckman, 1925 , W. plena (Buckman, 1926) , W. patefactor (Buckman, 1923) , and W. spinifera Buckman, 1920 , whose types come from the same bed, are almost undoubtedly only variants of a single biospecies. However, more material from the type area would be necessary to confirm such conjecture.

DISTRIBUTION

Chandler et al. (2006) showed that, in the type locality ( Inferior Oolite at South Main Road Quarry , Dundry , Avon , England), W. laeviuscula occurs in the last horizon (BJ-10b) of the Laeviuscula Zone and Subzone. The species has been frequently cited, although few typical specimens were figured except for the LT. The species appears to be restricted to the Laeviuscula Subzone and the base of the Propinquans Zone of Europe and Morocco. Subbetic specimens are from the Laeviuscula Zone and Subzone and the base of the Propinquans Zone ( Patella Subzone ) of the Sierra of Alta Coloma (JAC3, JAC3’ and JAC22 sections; Jaén Province).

Figures

FIG. 13. — A, Witchellia hyalina (Buckman, 1924) [M], JAC11.8.21, Propinquans Zone,Patella Subzone, Sierra de Alta Coloma (JAC11 section); B, Witchellia sayni Haug, 1893 [M], JAC11.(4-7).1, Laeviuscula Zone?, Sierra de Alta Coloma (JAC11 section); C, Witchellia laeviuscula (J. de C. Sowerby, 1824) [M], JAC3.71.2, Laeviuscula Subzone, Sierra de Alta Coloma (JAC3 section); D-F, Witchellia companyi n. sp. [M], JAC11.8.16 (HT), JAC11.8.22, JAC11.8.14, Propinquans Zone, Patella Subzone, Sierra de Alta Coloma (JAC11 section); G, H, Witchellia striata n. sp. [M]; G, JAC11.4.27 (HT), Laeviuscula Zone, Trigonalis Subzone, Sierra de Alta Coloma (JAC11 section); H, JAC4.36.1, Laeviuscula Zone, Sierra de Alta Coloma (JAC4 section). Scale bar: 1 cm.