Ammotectonica soproniensis (Strausz, 1960)

Harzhauser, Mathias & Landau, Bernard, 2023, The Architectonicidae and Mathildidae (Gastropoda, Heterobranchia) of the Miocene Paratethys Sea-victims of the Miocene Climatic Transition, Zootaxa 5370 (1), pp. 1-74 : 11-13

Ammotectonica soproniensis (Strausz, 1960)

Figs 6A 1 –A 3

* Solarium soproniense Roth L. in coll.—Strausz 1960: 349, pl. 20, figs 1, 3, 4.

Solarium soproniense Roth —Strausz 1962: 123, pl. 51, figs 11–13.

Solarium soproniense Roth in Strausz, 1960—Strausz 1966: 117, pl. 51, figs 11–13.

soproniense (Solarium) Roth in Strausz, 1960 — Bieler & Petit 2005: 64.

Type material, Holotype: M11, SL: 10 mm, MD: 23 mm, Mining and Geological Survey of Hungary) from the Badenian of Sopron ( Hungary). We have not been able to see the holotype. Therefore, we re-illustrate the figures of Strausz (1966), Figs 6A 1 –A 3 .

Revised description. Medium-sized, moderately flattened, lenticular shell with low conical spire and nearly flat spire whorls. Protoconch heterostrophic, medium-sized of 0.8 visible whorls. Teleoconch of 4.5 whorls. SSC very weak; UPC narrow, weakly beaded; LPC more prominent, smooth. MCs area smooth except for delicate, prosocline growth lines. Periphery strongly angulated, weakly keeled, faintly concave below keel. Base convex. IPC reduced to faint spiral thread. Outer basal field smooth; inner basal field with narrow, densely spaced axial folds, starting from poorly defined central spiral cord. UC numerous, relatively small of comparable shape and size to axial folds, delimited by narrow groove, overhanging umbilicus. Umbilicus very wide (~40% of MD). Aperture rhombic with marked peripheral angulation. Moderately deep CG and weak, moderately wide PG.

Discussion. Only the holotype is known, which was not available to us. The wide umbilicus and the characteristic narrow spiral band of axial folds and umbilical crenae separate Ammotectonica soproniensis very distinctly from all other Paratethyan Architectonicidae .

This species has an unusual character that is the poorly defined elevated spiral cord from which the folds start abruptly. Although the folds are thus sharply delimited, they are not delimited by a groove as typical for a PUC.

Ammotectonica deshayesi ( Michelotti, 1847) , from the Burdigalian of the Colli Torinesi ( Italy), has a comparable shape and sculpture but has a much broader smooth area on the basal field (Sacco 1892: pl. 2, fig. 29).

Paleoenvironment. The occurrence at Sopron suggests middle to outer neritic water depths (own data M.H.) .

Distribution. Known so far only from the middle Badenian (late Langhian) of the Central Paratethys Sea.

Central Paratethys Sea. Middle Miocene (Badenian): Eisenstadt-Sopron Basin: Sopron ( Hungary) (Strausz 1966).

Figures

FIGURE 1. Descriptive terms used in descriptions of Architectonicidae (modified from Bieler 1993).

FIGURE 3. Descriptive terms used in descriptions of Mathildidae.

FIGURE 6 A1–A3. Ammotectonica soproniensis (Strausz, 1960), holotype, M11, Sopron (Hungary), modified from Straus (1966).