Trigonostoma schroeckingeri ( Hoernes & Auinger, 1890 )

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

Trigonostoma schroeckingeri ( Hoernes & Auinger, 1890)

Figs 10H 1–H 3

Cancellaria (c. Trigonostoma ) Schroeckingeri nov. form.— Hoernes & Auinger 1890: 275, pl. 33, figs 12a–b.

Cancellaria (Gulia) geslini (Bast.) var. ornatissima Boettger, 1906: 50 .

Cancellaria (Ventrilia) geslini ornatissima (Boettger) — Zilch 1934: 260, pl. 17, fig. 23.

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

Studied and illustrated material. Figs 10H 1–H 3: specimen illustrated in Hoernes and Auinger (1890, pl. 33, figs 12a–b), CoŞteiu de Sus ( Romania), height: 26.0 mm, width: 20.7 mm, NHMW 1949/0003/0001, holotype by monotypy [note that the dimensions given in Hoernes & Auinger 1890 are incorrect].

Description: A broad shell consisting of five moderately convex whorls with conspicuous sutural shelf. The sculpture is delicate and homogenous, consisting of about ten primary cords with an intercalated secondary spiral thread between each pair of primary cords; these secondaries are hard to distinguish on the base. The spiral cords cross slightly prosocline axial ribs of similar strength. The intersections of axial and spiral cords are muricid-like scalloped, being most pronounced along the shoulder. The cancellate sculpture passes into the wide and deep umbilicus. Two narrow columellar folds appear on the straight columella, parietal and columellar calluses are hardly developed, and numerous delicate lirae appear within the outer lip. The protoconch is poorly preserved but suggests a low shape.

Discussion. The holotype of Cancellaria (Gulia) geslini (Bast.) var. ornatissima Boettger, 1906 represents a juvenile of Trigonostoma schroeckingeri and differs from the type only in its reduced axial sculpture. Janssen (1984a) considered Trigonostoma ornatissima ( Boettger, 1906) as synonym of the Miocene North Sea species Trigonostoma apertum ( Beyrich, 1856) . He correctly interpreted the specimen illustrated by Zilch (1934) as juvenile specimen and stated that it resembles juveniles of T. apertum . The shell, which Hoernes and Auinger (1890) had at hand when describing their Trigonostoma schroeckingeri , is clearly an adult shell, which agrees in size to adult shells of T. apertum . Aside from some resemblance concerning the flat sutural shelf, both taxa, however, are clearly not conspecific. Trigonostoma schroeckingeri has a much higher spire and a higher last whorl. Its sculpture is much more delicate and the convexity of the whorls is weaker.

Distribution. A rare species, which is known so far only from the early Badenian of the Transylvanian Basin.

Paratethys —Badenian: Transylvanian Basin ( Romania: CoŞteiu de Sus).