Chouteauoceratinae, Korn, 2025

Korn, Dieter, 2025, A revised classification of the Carboniferous and Permian Nautilida, European Journal of Taxonomy 1017, pp. 1-85 : 24-25

Subfamily Chouteauoceratinae subfam. nov.

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Fig. 12

Type genus

Chouteauoceras Miller & Garner, 1953

Diagnosis

Subfamily of the family Trigonoceratidae with cyrtoconic or gyroconic conch. Whorl profile compressed oval; venter rounded. Sculpture in the early species with longitudinal, equidistant ridges throughout ontogeny; advanced species with a reduction of spiral ridges. Suture line with broadly rounded lobes and saddles.

Etymology

The subfamily name refers to the type genus.

Included genera

Chouteauoceras Miller & Garner, 1953 (Tournaisian; 3 species).

Ungeroceras Sturgeon & Miller, 1948 (Moscovian; 1 species).

Parachouteauoceras Niko & Ozawa, 1997 (Gzhelian or Asselian; 1 species).

Remarks

The subfamily Chouteauoceratinae subfam. nov. contains genera that are not very well known. It is therefore uncertain whether the other two genera, in addition to the typical genus Chouteauoceras , are members of this subfamily. This is particularly true for the enigmatic Late Carboniferous genus Ungeroceras , newly described by Sturgeon & Miller (1948). This genus was synonymised by Murphy (1966) with the orthoconic genus Kionoceras Hyatt, 1884 . Sturgeon et al. (1997: 57) discussed the genus, concluding that it is probably a coiled nautiloid, possibly related to the stratigraphically older Tournaisian genus Chouteauoceras ( Miller & Garner 1953) . Loose coiling and a compressed whorl profile are accepted as the most important criteria ( Fig. 12 ). However, further research and new material may substantiate this hypothesis.

Figures

Fig. 12. Subfamily Chouteauoceratinae subfam. nov. Chouteauoceras americanum (Miller & Furnish, 1939), from Miller & Furnish (1939) and Miller & Garner (1953). Scale bar units = 1 mm.