Ethanoceras Kröger & Pohle 2021, gen. nov.

Genus Ethanoceras gen. nov.

urn:lsid:zoobank.org:act: 7D492453-6BC0-4F56-8DD4-806D508E9DD4

Ethanoceras solitudines gen. et sp. nov. from the Olenidsletta Member, V2 trilobite zone, Blackhillsian, Floian; by monotypy.

Longiconic orthocones with angle of expansion of ca 5°, with circular conch cross section; shell surface ornamented with distinctive, narrowly spaced transverse striae; strongly eccentrically positioned siphuncle with relative siphuncle diameter rSD ≈ 0.16; septal necks relatively long, s-shaped orthochoanitic to loxochoanitic; connecting rings are thick and slightly s-shaped in sagittal section; cameral and endosiphuncular deposits not known.

Referring to Ethan, the name of a Svalbard reindeer, Rangifer tarandus platyrhynchus (Vrolik, 1829), browsing at the Profilbekken area during the summer of 2017.

Ethanoceras gen. nov. differs from other Rioceratidae in having a siphuncle that is completely detached from the conch margin. Specimens of Ethanoceras gen. nov. with conch cross section diameter <6 mm can be distinguished from Bactroceras boliviensis Aubrechtová, 2015 in having only a very weak transverse ornamentation and a distinctive septal neck. Nevadaceras conicum Flower, 1968 differs in having a compressed conch cross section and a slightly expanded siphuncle with thin connecting rings. In Michelinoceras toquimense Flower, 1968 the siphuncle is strictly tubular and eccentrically positioned on the convex side of the conch curvature. The shape of the septal necks of Ethanoceras solitudines gen. et sp. nov. is unique among the Rioceratidae and related taxa; it is morphologically transitional to species with relatively long and partly curved septal necks such as Hemichoanella canningi Teichert & Glenister, 1954 and Lebetoceras oepiki Teichert & Glenister, 1954, known from late Tremadocian–early Floian beds of the Emanuel Formation, Western Australia.