Maccoyoceras saharensis, Korn & Bockwinkel, 2022

Korn, Dieter & Bockwinkel, Jürgen, 2022, Early Carboniferous nautiloids from the Central Sahara, southern Algeria, European Journal of Taxonomy 831, pp. 67-108 : 99-101

Maccoyoceras saharensis sp. nov.

urn:lsid:zoobank.org:act:029ECCD2-153E-4624-8C6B-B1D24CF0E940

Figs 26–27 , Table 15

Diagnosis

Species of Maccoyoceras with subquadrate whorl profile (ww/wh ~1.05), venter slightly flattened, ventrolateral shoulder broadly rounded. Whorls not embracing.

Etymology

Named after the occurrence in the Sahara Desert.

Type material

Holotype ALGERIA • Mouydir , south of Oued Temertasset (locality MOU-A); Argiles de Teguentour (Upper Pericyclus-Progoniatites Assemblage; early late Tournaisian); Korn et al. 2002 Coll.; illustrated in Fig. 26A ; MB.C.30480.1 .

Paratypes ALGERIA • 1 specimen; Mouydir , south of Oued Temertasset (locality MOU-D1); Argiles de Teguentour (Upper Pericyclus-Progoniatites Assemblage; early late Tournaisian); Korn et al. 2002 Coll.; illustrated in Fig. 26B ; MB.C.30481 • 7 specimens; Mouydir , south of Oued Temertasset (localities MOU-A, MOU-B5, MOU-E07, MOU-D2); Argiles de Teguentour (Upper Pericyclus-Progoniatites Assemblage; early late Tournaisian); Korn et al. 2002 Coll.; MB.C.30480.2 – MB.C.30480.3 , MB.C.30482.1 – MB.C.30482.2 , MB.C.30483.1 – MB.C.30483.2 , MB.C.30484 .

Description

Holotype MB.C.30480.1 is the fragment of a phragmocone of a quarter whorl length ( Fig. 26A ); it has a whorl height of 16 mm. The whorl profile is subquadratic with flattened, very weakly convergent flanks, a broadly rounded venter and a broadly rounded dorsum ( Fig. 27A ). The internal mould shows no ornament, but very faint remnants of spiral striation are visible. The suture line extends with a slight

depression on the venter, a slightly deeper, very broadly rounded lobe on the flank and a very shallow internal lobe ( Fig. 27B ).

Paratype MB.C.30481 shows the chambered remains of two whorls that touch but do not overlap ( Fig. 26B ). On the outer whorl with 12 mm whorl height, the profile is subquadrate (ww/wh =1.04) with a wider, flattened venter, weakly divergent, also flattened flanks and a more tightly rounded dorsum ( Fig. 27C ). The penultimate whorl, 3.8 mm high, is rounded-triangular in profile and somewhat depressed (ww/wh =1.28). The suture line is similar to that of the holotype, but shows a higher ventral area with a slightly deeper external lobe ( Fig. 27D ).

Remarks

Maccoyoceras saharensis sp. nov. differs from the other species of the genus by the whorl profile form with a strongly rounded ventrolateral shoulder. Another difference could be the strength of the ornament; in M. saharensis sp. nov. no spiral lines were impressed into the internal mould. However, since no shell specimens of the new species are known, it is impossible to say whether spiral lines were actually present. It is therefore also possible that the new species belongs to another genus, for example Lispoceras .

Figures

Fig. 26. Maccoyoceras saharensis sp. nov. from Oued Temertasset (all Korn et al. 2002 Coll.). A. Holotype MB.C.30480.1. B. Paratype MB.C.30481. Scale bar units =1 mm.

Fig. 27. Maccoyoceras saharensis sp. nov. from Oued Temertasset (both Korn et al. 2002 Coll.). A. Whorl profile of holotype MB.C.30480.1. B. Suture line of holotype MB.C.30480.1, at ww =16.2 mm, wh=14.8 mm. C. Whorl profile of paratype MB.C.30481. D. Suture line of paratype MB.C.30481, at ww=10.9 mm, wh= 14.8 mm. Scale bar units =1 mm.

Tables

Table 15. Conch dimensions (in mm) and ratios of Maccoyoceras saharensis sp. nov.

Specimen	dm	ww	wh	uw	ah	ww/dm	ww/wh	uw/dm	WER	IZW
MB.C.30480.1	–	16.4	15.7	–	–	–	1.04	–	–	–
MB.C.30481	–	11.7	11.2	–	–	–	1.04	–	–	–