Genus Glabrocingulum Thomas, 1940

Type species. Glabrocingulum beggi Thomas, 1940; Carboniferous, Scotland.

Diagnosis. Low- to moderately high-spired and turbiniform shell shape. The upper whorl surface forming an angle of <45 ^Ǫ with the selenizone located on the upper edge of whorl face. Sutures sharply defined. Upper whorl face with both spiral and collabral ornament; most strongly developed near the suture, weakest near the selenizone. Anomphalus to widely phaneromphalus, with or without funicle.

Remarks. These specimens resemble the Permian genera Wannerispira, Ananias and Glabrocingulum, and the Triassic genus Kamupena. They differ from Wannerispira by possessing a selenizone in the upper third of the whorl, and only having two rather than three strong spiral ribs; from Ananias by being low- rather than high-spired and having a less conspicuous and thinner concave band below the selenizone; and from Kamupena by lacking a strong umbilical callus plug. These specimens also differ from other neilsoniines by having spiral ribs and no axial ornamentation, and by being less elongated. Another genus with a comparable whorl profile is Rhaphistomella, which has been considered a synonym of Glabrocingulum (Batten 1989; Erwin & Pan 1996), but it differs from these specimens by the absence of a prominent medial concave band and a more strongly nodulose keel under the suture. These specimens are therefore assigned to the genus Glabrocingulum.

Wannerispira is the only other unequivocal eotomariid genus to have been reported from the Early Triassic (Kaim et al. 2010; Hautmann et al. 2015), and belongs to the Subfamily Neilsoniinae. Since Glabrocingulum, in contrast, is dextral, low- rather than high-spired, and with a moderately deep slit developing into a selenizone with rounded margins, it belongs within the Subfamily Eotomariinae. These specimens represent the first Early Triassic record of the Subfamily Eotomariinae and are the first Early Triassic record of the genus Glabrocingulum, which is rarely recorded after the Permian period.