Sonninia (Euhoploceras) nannomorpha (Buckman, 1923) Sandoval, José, 2022

Sandoval, José, 2022, Sonniniidae Ammonitina, Middle Jurassic from Southern Spain: taxonomic, biostratigraphical and palaeobiogeographical analysis, Geodiversitas 44 (27), pp. 801-851 : 816-817

Sonninia (Euhoploceras) nannomorpha (Buckman, 1923) , n. comb. [m]

( Fig. 9B )

Nannoceras nannomorphum Buckman, 1923 : T.A. 5, pl. 445. —– Dietze et al. 2011a: 226, pl. 7, figs 18-20 (HT refigured).

Nannoceras sp. cf. N. nannomorphum – Sadki et al. 2015: 61, pl. 14, fig. C.

MATERIAL EXAMINED. — JAC3. R.27 , JAC22.5.1 , MOD.X.319 , MOD.X.320 , MOD.X.321 , MOD.X.322 , MOD.X.323 , MOD.X.330 , MOD.X.332 and MOD.X.337.

MEASUREMENTS. — See Table 7.

DESCRIPTION

Small microconchs with moderately evolute coiling.The whorl section, being depressed suboval in the innermost whorls, gradually becomes compressed subrectangular in the adult BC. The umbilicus is wide and shallow with a rounded umbilical edge. The ventral region is weakly tabulated with a broad, low keel bordered by small sulci, which persist up to the vicinity of the adult peristome bearing spatulate lateral lappets. The ribs are usually simple, very rarely grouped near the umbilical edge or divided on the flanks, subradial or retroverse but slightly sinuous, gradually thickening from the umbilical edge to the ventrolateral margin.At the BC end, the ribs weaken but do not disappear completely.The inner whorls can be tuberculate.The septal suture is not well preserved in the available specimens.

REMARKS

As indicated above regarding the genus, Nannoceras is the dimorphic partner of S. (Euploceras) and consequently “ N. ” nannomorphum should included in this genus.

DISTRIBUTION

The HT of “ N. ” nannomorphum comes from the Discites Zone of Bradford Abbas Fossil Bed, near Yeovil, England (Buckman 1923; Dietze et al. 2011a), but according to Callomon & Chandler (1990) it is common at the base of Ovale Zone (Bj-4 horizon) of southern England. The species occurs in the Discites-lower part of the Ovale zones of the Atlas, Morocco ( Sadki 1996), in the Discites Zone of the Iberian Range, Spain (Fernández-López 1985), and in the Discites Zone? of Luxembourg ( Sadki et al. 2015). Subbetic specimens are from the Discites Zone of the MOD section, Montillana (Granada Province) and from the base of the Ovale zone of JAC22 section, Campillo de Arenas (Jaén Province).

Figures

FIG. 9. — A, Sonninia (Sonninia) schlumbergeri Haug, 1893 [m], JAC4.39.10,Laeviuscula Zone,Sierra de Alta Coloma (JAC4 section); B, Sonninia (Euhoploceras) nannomorpha (Buckman, 1923), n. comb. ([m], JAC22.5.9, Ovale Zone, Sierra de Alta Coloma (JAC22 section); C, Sonninia (Papilliceras) arenata (Quenstedt, 1886) [M], A.9.9.2.2-1, Propinquans Zone?, Sierra de Alta Coloma; D, Sonninia (Papilliceras?) sp. [M], JAC22.6.13, Ovale Zone, Sierra de Alta Coloma (JAC22