Vestinautilus Ryckholt 1852

Genus Vestinautilus Ryckholt, 1852 Type species Nautilus Koninckii d’Orbigny, 1850; subsequent designation by Hyatt (1884). Diagnosis Genus of the family Trigonoceratidae with usually thickly discoidal to pachyconic evolute conch; whorls slightly impressed or without contact; whorl profile rounded triangular or trapezoidal with flattened or weakly concave venter and pronounced ventrolateral shoulder. Conch rapidly increasing in height with a high coiling rate (WER usually higher than 2.20). Ornament with fine lines and very coarse spiral ridges around the ventrolateral shoulder, sometimes also on the venter. Septa without inflexions, moderately concave. Suture line slightly sinuous with small external lobes, sometimes with lateral and internal lobes. Siphuncle small with subcentral position (after Kummel 1964; Shimansky 1967; emended). Included species Reviews of the species belonging to Vestinautilus have been given by Histon (1999), Korn et al. (2022) and Korn & Bockwinkel (2022). Species of the genus have been described from the following regions: North America (Winchell 1862): Nautilus (Trematodiscus) altidorsalis Winchell, 1862, Michigan. Northern and Central Europe (Sowerby 1825; d’Orbigny 1842 –1851; de Koninck 1844; Foord 1891, 1900; Turner 1954): Nautilus biangulatus Sowerby, 1825, Southwest England; Nautilus cariniferus Sowerby, 1825, Ireland; Vestinautilus crassimarginatus Foord, 1900, Ireland; Vestinautilus crateriformis Foord, 1900, Ireland; Triboloceras formosum Foord, 1900, Ireland; Nautilus Koninckii d’Orbigny, 1850, Belgium; Nautilus multicarinatus Sowerby, 1825, Ireland; Coelonautilus paucicarinatus Foord, 1891, Ireland; Nautilus pinguis de Koninck, 1844, Belgium; Vestinautilus semiglaber Foord, 1900, Ireland; Vestinautilus semiplicatus Foord, 1900, Ireland; Subvestinautilus simulans Turner, 1954, Isle of Man. North Africa(Korn & Bockwinkel 2022; Korn et al. 2022): Vestinautilus angulatus Korn & Bockwinkel, 2022, Algeria; Vestinautilus bicristatus Korn & Bockwinkel, 2022, Algeria; Vestinautilus concinnus Korn, Miao & Bockwinkel, 2022, Algeria; Vestinautilus inflexus Korn & Bockwinkel, 2022, Algeria; Vestinautilus padus Korn, Miao & Bockwinkel, 2022, Algeria; Vestinautilus papilio Korn & Bockwinkel, 2022, Algeria; Vestinautilus kesslerae sp. nov., Anti-Atlas. West Russia, Urals and Kazakhstan (Tsvetaeva 1898; Shimansky 1967): Subvestinautilus maritimus Shimansky, 1967, Middle Urals; Subvestinautilus rector Shimansky, 1967, Kazakhstan; Coelonautilus znamenskianus Tzwetaeva, 1898, West Russia. Remarks Turner (1954) revised Vestinautilus and specifically restricted the genus “to forms resembling the typespecies in possessing a venter concave or channelled at some stage of growth, a broad, depressed whorlsection, and a conch ornamented with spiral ribs, lirae and sulci.” At the same time, he introduced the new genus Subvestinautilus, which he classified in the family Temnocheilidae. He stated that “the genus much resembles Vestinautilus … in shape but lacks a concave or channelled venter at any stage of development.” However, since he regarded Vestinautilus as belonging to the family Triboloceratidae, he indirectly saw the close morphological similarity with it as the result of convergent evolution. This opinion was followed by Shimansky (1967) and Histon (1999), albeit with a different family attribution. However, Dzik (1984) rejected this concept, treating Subvestinautilus as a synonym of Vestinautilus. We do not accept the separation of the two genera. The variable shape of the venter, which changes in some species during ontogeny, can hardly be regarded as a distinguishing criterion for these genera. We therefore assign species with coarse spiral ridges and a broad trapezoidal whorl profile, whether with a concave or convex venter, to Vestinautilus.Published as part of Korn, Dieter & Klug, Christian, 2023, Early Carboniferous coiled nautiloids from the Anti-Atlas (Morocco), pp. 156-194 in European Journal of Taxonomy 885 on pages 167-168, DOI: 10.5852/ejt.2023.885.2199, http://zenodo.org/record/822241