Vestinautilus inflexus Korn & Bockwinkel 2022, sp. nov.
Creators: name: Korn, Dieter
name: Bockwinkel, Jürgen
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Cephalopoda
Nautilida
Trigonoceratidae
Vestinautilus
Vestinautilus inflexus

description: Vestinautilus inflexus sp. nov.
urn:lsid:zoobank.org:act: 7AEE52F5-6984-4497-8DC0-B23E712C1CF9
Figs 18–19, Table 10
Diagnosis
Species of Vestinautilus with moderately depressed, rounded-triangular whorl profile (ww/wh ~ 1.95), venter weakly flattened, smooth, ventrolateral shoulder angular. Whorls not embracing. Ornament with three weak but sharp ridges on the flank. Septa inflexed to produce a deep external lobe.
Etymology
From the Latin ‘ inflexus ’, referring to the incurved septum.
Type material
Holotype ALGERIA • 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. 18B; MB.C.30472.1.
Paratypes ALGERIA • 2 specimens; 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. 18A, C; MB.C.30472.2 – MB.C.30472.3.
Description
Holotype MB.C.30472.1 is a phragmocone fragment from a quarter whorl with 15 mm whorl height (Fig. 18B). It has a moderately depressed whorl profile (ww/wh = 1.94) with a flattened venter and broadly rounded lateral and dorsal zones. The ventrolateral shoulder is subangular and reinforced by two sharp longitudinal ridges; there are two more, weaker ridges on the outer flank (Fig. 19B). The suture line shows a broad external lobe, flattened at the base. This particular shape is caused by an inflexion of the septum on the middle of the venter. There is a narrowly rounded saddle on the ventrolateral shoulder and a shallow, broadly rounded lobe on the flank (Fig. 19C).
Paratype MB.C.30472.2 is a desert-polished specimen with half a whorl preserved; it has a diameter of 24.5 mm (Fig. 18A). It was sectioned and shows one and a half whorls, which possess a similar profile. The last preserved whorl does, at 24 mm conch diameter, not touch the preceding, but this may be caused by the lack of the original shell wall (Fig. 19A). The longitudinal ridges are only barely visible and rather weak when compared with the holotype. The suture line shows a deeper external lobe, which is less flattened at the base.
The smaller paratype MB.C.30472.3 (Fig. 18C) with 6 mm whorl height has a less depressed whorl profile, but shows very clearly the ventral inflexion of the septum and the resulting very deep external lobe (Fig. 19E).
Remarks
Vestinautilus inflexus sp. nov. belongs to the species of the genus with a moderately depressed whorl profile (ww/wh ~1.95) and thus ranges between the more slender species V. angulatus sp. nov. (ww/wh ~1.50) as well as V. papilio sp. nov. (ww/wh ~ 1.70) and the stouter species V. bicristatus sp. nov. (ww/ wh ~2.15). The new species differs from those species of the genus with a similar whorl profile in the very weak longitudinal ridges.
description: Published as part of Korn, Dieter & Bockwinkel, Jürgen, 2022, Early Carboniferous nautiloids from the Central Sahara, southern Algeria, pp. 67-108 in European Journal of Taxonomy 831 on pages 89-91, DOI: 10.5852/ejt.2022.831.1871, http://zenodo.org/record/6885198