Goniatites sphaericus (Sowerby, 1814)

Korn, Dieter & Ebbighausen, Volker, 2025, Late Viséan (Mississippian) ammonoids (Cephalopoda) from the Central Moroccan Meseta, European Journal of Taxonomy 989, pp. 50-93 : 59-65

publication ID	https://doi.org/10.5852/ejt.2025.989.2885
publication LSID	lsid:zoobank.org:pub:9D91C7A1-F5B2-42D2-BC13-F3290E4679EF
DOI	https://doi.org/10.5281/zenodo.15309850
persistent identifier	https://treatment.plazi.org/id/03B49601-FFA0-FF9D-D21B-FB49FE77FB00
treatment provided by	Plazi
scientific name	Goniatites sphaericus (Sowerby, 1814)
status

Treatment

Goniatites sphaericus (Sowerby, 1814) View in CoL

Figs 7–11 View Fig View Fig View Fig View Fig View Fig ; Tables 3–5 View Table 3 View Table 4 View Table 5 , A 2 View Table 2

Conchyliolithus Nautilites ( sphaericus ) Martin, 1809: pl. 7 figs 3–5.

Ammonites sphaericus Sowerby, 1814: 116 , pl. 53 fig. 2.

Glyphioceras crenistria var. globoides Schmidt, 1925: 566 , pl. 21 fig. 1.

Goniatites crenistria View in CoL – Delépine 1941: 66, pl. 4 figs 2–3.

Goniatites sphaericus View in CoL – Stubblefield 1951: 120, pl. 7 fig. 1. — Korn 1988: 81, text-figs 28, 29c; 2017: 342, text-figs 5–12 (for more synonymy). — Nikolaeva 2008: 7, pl. 8 fig. 5, text-fig. 1.8–10.

Goniatites fimbriatus View in CoL – Korn 1988: 89, pl. 20 figs 1–7, pl. 21 figs 1–6, pl. 22 figs 1–4, text-figs 35–36, 37a–c, 38a–b; 1990: 32, pl. 8 figs 1–12, pl. 9 figs 1–11, pl. 10 figs 1–5, text-fig. 11a–d. — Nikolaeva 2008: pl. 14 figs 3, 5, pl. 15 figs 1–2, text-fig. 1.11.

Diagnosis (from Korn 2017, emended)

Species of Goniatites reaching a conch diameter of 120 mm. Conch globular at 10 mm diameter (ww/ dm = 0.90–1.10), thickly pachyconic at 30 mm diameter (ww/dm = 0.75–0.85) and thinly pachyconic at 50 mm diameter (ww/dm = 0.65–0.70). Umbilicus very narrow at 10 mm dm (uw/dm = 0.05–0.15), in the adult stage slightly opening; umbilical wall rounded. Coiling rate in the adult stage low (WER ~ 1.50). Ornamentation with crenulated rursiradiate and biconvex growth lines with moderate dorsolateral projection and lower ventrolateral projection; external sinus shallow. Delicate spiral lines around the umbilicus caused by crenulation of growth lines. Suture line with a V-shaped, moderately narrow external lobe (0.60 of the external lobe depth, 1.10–1.20 of the adventive lobe width) and a moderately high median saddle (0.35–0.40 of the external lobe depth); E lobe Y-shaped in very large stages. Flanks of the external lobe weakly sinuous, ventrolateral saddle acute, adventive lobe V-shaped with weakly convex flanks.

Type material

Holotype

UNITED KINGDOM – Derbyshire • Derbyshire, without more precise locality information; ‘greyish black swinestone’ ( Late Viséan ); Martin Coll.; NHM 43871 ; illustrated by Stubblefield (1951: pl. 7 fig. 1) and Korn (1988: text-fig. 28; 2017: text-fig. 5a).

Material examined

MOROCCO – Central Meseta • 98 specs; Sidi Lamine; sample 3, Goniatites sphaericus Zone ( Late Viséan ); 2007; Korn and Ebbighausen leg.; MB.C. 32204.1 to MB.C. 32204.98 • 28 specs; same data as for preceding; 2009; Korn and Ebbighausen leg.; MB.C. 32205.1 to MB.C. 32205.28 • 23 specs; Sidi Lamine; sample 3, Goniatites sphaericus Zone ( Late Viséan ); 2010; Korn and Ebbighausen leg.; MB.C. 32206.1 to MB.C. 32206.23 • 17 specs; same data as for preceding; 2011; Korn and Ebbighausen leg.; MB.C. 32207.1 to MB.C. 32207.17 • 7 specs; Dechra Aït Abdallah; sample 1, Goniatites sphaericus Zone ( Late Viséan ); 2009; Korn and Ebbighausen leg.; MB.C. 32212.1 to MB.C. 32212.7 • 8 specs; same data as for preceding; sample 2; 2009; Korn and Ebbighausen leg.; MB.C. 32213.1 to MB.C. 32213.8 • 9 specs; same data as for preceding; sample 3; 2009; Korn and Ebbighausen leg.; MB.C. 32214.1 to MB.C. 32214.9 • 6 specs; same data as for preceding; float material; 1949; H. and G. Termier leg.; MB.C. 32215.1 to MB.C. 32215.6 • 1 spec.; Afroug; float material, Goniatites sphaericus Zone ( Late Viséan ); 2009; Korn and Ebbighausen leg.; MB.C. 32221 .

Description

A detailed description of specimens from various regions, including an analysis of intraspecific variation, has been provided by Korn (2017). Therefore, only certain aspects of variation within the sample from Sidi Lamine are highlighted here. Goniatites sphaericus occurs in at least three variants at Sidi Lamine, which differ in the ratio of whorl width to conch diameter in the ontogenetic interval above 20 mm conch diameter:

Variant 1 is represented by specimens MB.C.32205.1 ( Fig. 7A View Fig ), MB.C.32206.1 ( Fig. 7B View Fig ), MB.C.32206.2 ( Fig. 7C View Fig ), MB.C.32204.1 ( Fig. 7D View Fig ) and the cross sections of specimens MB.C.32206.5 and MB.C.32206.6 ( Fig. 11A–B View Fig ). This variant can be considered as the intermediate, standard form. It shows a thickly pachyconic conch (ww/dm ~ 0.75) at a diameter of 40 mm. However, this does not imply that the inner whorls share the same geometry and ontogeny, as seen in the two cross sections. For instance, specimen MB.C.32206.5 has a low coiling rate at 3 mm diameter (WER ~ 1.60), while specimen MB.C.32206.6 has a significantly higher coiling rate (WER ~ 1.85). Other differences include MB.C.32206.5 having a more broadly rounded venter, while MB.C.32206.6 possesses an incurved umbilical wall. It seems impossible to assign adult specimens such as MB.C.32205.1 and MB.C.32207.4 to either of these subvariants without sectioning the conch.

Variant 2 is represented by specimens MB.C.32207.1 ( Fig. 8A View Fig ), MB.C.32205.2 ( Fig. 8B View Fig ), MB.C.32206.3 ( Fig. 8C View Fig ) and MB.C.32206.4 ( Fig. 8D View Fig ). This variant is characterised by the most slender conch; at a conch diameter of 38 mm, specimen MB.C.32207.1 has a ww/dm value of just 0.67.

Variant 3 is represented by specimens MB.C.32207.2 ( Fig. 9A View Fig ), MB.C.32207.3 ( Fig. 9B View Fig ) and MB.C.32204.2 ( Fig. 9C View Fig ) and the cross sections of specimen MB.C.32206.7 ( Fig. 11C View Fig ). This variant is distinguished by a stout conch; for example, at 36 mm diameter, specimen MB.C.32207.3 has a ww/dm value of 0.79, and at 22 mm conch diameter, specimen Sil3 is nearly spherical (ww/dm = 0.94).

The three variants can also be recognised in the material from Dechra Aït Abdallah ( Fig. 10 View Fig ). At this locality, the first variant, which occupies the middle of the morphological spectrum, is the most commonly represented.

Nearly all specimens display a very similar ornamentation, characterised by strongly crenulated growth lines. These growth lines exhibit a low dorsolateral projection, are weakly curved backwards on the flank, and form a broad, shallow ventral sinus. The pronounced crenulation gives rise to clearly visible spiral lines, particularly noticeable in specimen MB.C.32204.1 ( Fig. 7D View Fig ), where continuous fine spiral lines have developed. These spiral lines are significantly narrower than the spaces separating them.

Remarks

The nomenclatorial history of the species and the type specimen was outlined in detail by Stubblefield (1951).

The material from Sidi Lamine exhibits very similar patterns of morphological variation to those recognised in the Rhenish Mountains ( Korn 1988, 1990, 2017). This variation primarily concerns the ww/dm ratio, which is particularly pronounced in the inner whorls, though adult conchs also vary in this respect. Another aspect of variation is the coiling rate, although this is mainly evident during the juvenile stage between 2 and 7 mm conch diameter. Above 10 mm conch diameter, the whorl expansion rate stabilises at around 1.50 in all specimens. This relatively low coiling rate serves as the most reliable criterion for distinguishing G. sphaericus from C. crenistria , which has a whorl expansion rate of 1.70 or higher in the adult stage.