Vestinautilus Ryckholt, 1852

Korn, Dieter, Miao, Luyi & Bockwinkel, Jürgen, 2022, The nautiloids from the Early Carboniferous Dalle à Merocanites of Timimoun, western Algeria, European Journal of Taxonomy 789, pp. 104-129 : 120-121

Genus Vestinautilus Ryckholt, 1852

Type species

Nautilus Koninckii d’Orbigny, 1850 ; subsequent designation by Hyatt (1883 –1884).

Diagnosis

Genus of the family Trigonoceratidae with evolute conch; whorls slightly impressed; whorl profile rounded triangular or trapezoidal with flattened or weakly concave venter and pronounced ventrolateral shoulder. Ornament with fine lines and very coarse spiral ridges around the ventrolateral shoulder, sometimes also on the venter. Suture line slightly sinuous. Siphuncle small with subcentral position (after Kummel 1964; emended).

Included species

Nautilus (Trematodiscus) altidorsalis Winchell, 1862 , Michigan; Nautilus biangulatus Sowerby, 1825 , Southwest England; Nautilus cariniferus Sowerby, 1825 , Ireland; Vestinautilus concinnus sp. nov. Algeria; Triboloceras formosum Foord, 1900, Ireland; Nautilus Koninckii d’Orbigny, 1850 , Belgium; Nautilus multicarinatus Sowerby, 1825 , Ireland; Vestinautilus padus sp. nov., Algeria; Coelonautilus paucicarinatus Foord, 1891 , Ireland; Nautilus pinguis de Koninck, 1844 , Belgium; Vestinautilus semiglaber Foord, 1900 , Ireland; Vestinautilus semiplicatus Foord, 1900 , Ireland.

Remarks

When Turner (1954) revised the genus Vestinautilus , he explicitly restricted the genus “to forms resembling the type species in possessing a venter concave or channelled at some stage of growth, a broad, depressed whorl profile, and a conch ornamented with spiral ribs, lirae and sulci.” At the same time, he introduced the new genus Subvestinautilus, which he placed in the family Temnocheilidae Mojsisovics, 1902 . 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 Hyatt, 1884 , he indirectly regarded the close morphological similarity as a result of convergent evolution. This opinion was followed (albeit with other family names) by Shimansky (1967) and Histon (1999), but rejected by Dzik (1984), who treated Subvestinautilus as a synonym of Vestinautilus .

Here, we accept the separation of the two genera, but not the restrictive practice of Turner (1954), who considered the ventral shape (concave or convex) as the distinguishing character. The rather variable shape of the venter, which often changes throughout ontogeny in some of the species, can hardly be regarded as a criterion for distinguishing between the two families. We therefore assign those species

with coarse spiral ridges and a broad trapezoidal whorl profile, whether they possess a concave or convex venter, to Vestinautilus .

Stratigraphic range

Late Tournaisian to Viséan.