Trigonostoma exampullaceum ( Sacco, 1894 ) Harzhauser & Landau, 2012

Harzhauser, Mathias & Landau, Bernard, 2012, A revision of the Neogene Cancellariid Gastropods of the Paratethys Sea 3472, Zootaxa 3472, pp. 1-71 : 56-57

Trigonostoma exampullaceum ( Sacco, 1894) nov. comb.

Figs 10G 1–G 3

Cancellaria ampullacea Brocc. — Hörnes 1848: 19.

Cancellaria ampullacea Brocc. var.—Hörnes 1854: 321, pl. 35, figs. 4a–b [non Voluta ampullacea Brocchi, 1814 ].

Cancellaria (a. Trigonostoma ) ampullacea Brocc. — Hoernes & Auinger 1890: 275.

Cancellaria (Trigonostoma) gradatum forma exampullacea Sacco, 1894: 10.

Cancellaria (Trigonostoma) ampullacea Brocchi — Sieber 1936: 80.

Trigonostoma (Trigonostoma) ampullaceum (Brocchi) — Schultz 1998: 70, pl. 28, fig. 13 [non Voluta ampullacea Brocchi, 1814 ].

non Trigonostoma ampullaceum Brocc. — Friedberg 1914: 250, pl. 15, fig. 13 [= exgeslini Sacco, 1894 )

Type material. NHM Vienna ( Austria); see below for details .

Studied material. 9 spec. Enzesfeld-Gainfarn-Steinebrunn (mixed lot) ( Austria) NHMW 1846 /0037/0289; 27 spec. Grund ( Austria) NHMW 1550 / 0002/0048, NHMW 1863 / 0015/1274, NHMW 1968 / 0001/0229; 1. spec. Hrušovany (Czech Rep.) NHMW 1869 /0019/0006.

Illustrated material. Figs 10G 1–G 3: syntype illustrated in Hörnes (1854, pl. 35, figs 4a–c), Enzesfeld ( Austria), height: 19.1 mm, width: 14.7 mm, NHMW 1846 /0037/0289.

Description: A small species, which ranges constantly between 15–20 mm. Shape and sculpture are rather constant as well, being characterised by a low shell with strongly gradate spire and 10–12 prosocline axial ribs on the last whorl, of which the last ones are varicose. Thin and raised, regularly spaced spiral cords overrun the axial ribs and form elongate rectangulate interspaces between the cords. The umbilicus is deep and moderately wide; two columellar folds are sometimes joined by a weak third anterior fold. The paucispiral protoconch is poorly preserved but seems to consist of less than two whorls with depressed initial part and high and weakly convex last whorl.

Discussion. The overall shape with scalate spire, the deeply impressed sutures, the triangular aperture and the wide umbilicus require a placement in Trigonostoma (cf. Verhecken 2011). The Pliocene Trigonostoma ampullaceum ( Brocchi, 1814) is distinctly larger, has fewer axial ribs, a more convex last whorl and a lower spire (cf. Rossi–Ronchetti 1955; Chirli 2002). The next available name for the Paratethyan species was proposed by Sacco (1894), who referred to the specimen illustrated as fig. 4 in Hörnes (1854, pl. 35) when introducing the name exampullacea as form of Trigonostoma gradata (Hörnes) .

The Pliocene Trigonostoma parvotriangula Sacco (1894) [see type in Ferrero Mortara et al. (1984); more shells are illustrated as T. umbilicaris in Chirli (2002)] might represent a related species. It differs from T. exampullaceum in its larger size and the fewer and coarser axial ribs and the wider umbilicus.

Distribution. Only known from the Paratethys, where it lived during the early and middle Badenian. It is not known from the northern Paratethyan basins.

Paratethys —Badenian: North Alpine Foreland Basin ( Austria: Grund); Vienna Basin ( Czech Republic: Hrušovany; Austria: Steinebrunn, Gainfarn, Enzesfeld, Grinzing).