Ammotectonica gregorovae Harzhauser & Landau 2023, nov. sp.
Creators: name: Harzhauser, Mathias
name: Landau, Bernard
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Heterostropha
Mathildidae
Ammotectonica
Ammotectonica gregorovae

description: Ammotectonica gregorovae nov. sp.
Figs 4A, 5A–D
Type material. Holotype: NHMW 1865 /0015/0112, SL: 7.5 mm, MD: 15.2 mm, Lysice (Czech Republic), Figs 5A 1 –A 3. Paratypes: NHMW 1862 /0029/0078a, SL: 5.2 mm, MD: 15.1 mm, Rudice (Czech Republic), Figs 5B 1 –B 3. NHMW 1862 /0029/0078b, SL: 7.7 mm, MD: 18.1 mm, Rudice (Czech Republic), Figs 5C 1 –C 3. NHMW 1862 /0029/0078c, SL: 6.0 mm, MD: 15.0 mm, Rudice (Czech Republic), Figs 4A, 5D 1 –D 3.
Additional material. 6 spec. NHMW 1864 /0001/381, Jaroměřice (Czech Republic); 2 spec., NHMW 1862 /0029/0080, Rudice (Czech Republic).
Type locality. Lysice (Czech Republic).
Type stratum. Silty sand of a lateral equivalent of the Baden Formation.
Age. Middle Miocene, early/middle Badenian (Langhian).
Etymology. In honor of Růžena Gregorova, Moravské zemské muzeum, Brno (Czech Republic), in recognition of her contributions on Paratethyan ichthyology.
Diagnosis. Medium-sized, not very solid, moderately flattened lenticular shell with low conical spire and smooth SSC and LPC and beaded UPC. Characterized by strongly convex, nearly smooth base with axial folds and hardly delimited UC.
Description. Medium-sized, moderately flattened lenticular shell with low conical spire. Protoconch medium-sized, heterostrophic, 0.8 whorls visible (diameter 0.8 mm). Teleoconch of 4.5 whorls. First teleoconch whorl flat with subsutural row of beads and two rows of beads along periphery. MCs area of later teleoconch whorls smooth except for numerous delicate spiral threads and distinct prosocline growth lines. UPC and LPC prominent, beaded. Beads of UPC weakening but usually persisting to penultimate or last whorls. Beads on LPC fading out earlier. LPC prominent with flat top on dorsal side, forming weakly protruding rounded keel. Periphery angulated. Base convex with weakly concave area below keel. IPC subobsolete replaced by several delicate spiral threads. Basal field smooth with few irregular delicate spiral threads and axial folds, which strengthen towards umbilicus. Shorter secondary axial fold often intercalated between primaries, forming a somewhat axially bifurcate pattern. No PUC developed. UC blunt, tubercular, overhanging umbilicus. UC weakly delimited from axial folds, in some specimens separated from axial folds on basal field by weak and shallow groove, which may be largely reduced. Umbilicus very wide (35–38% of MD). Umbilical wall bearing fine, prosocline growth lines. Aperture small, subquadratic, angled at LPC with moderately deep CG and weak, wide PG.
Discussion. Ammotectonica soproniensis (Strausz, 1960), from the Badenian of Sopron (Hungary), is morphologically close to A. gregorovae but differs in its distinct mid-whorl axial ribs and the wider umbilicus. It develops a well-defined PUC of sharp axial folds, which are separated from the UC by a deep spiral groove. Its basal field and periphery are much narrower in basal view than in A. gregorovae.
The Paratethyan Ammotectonica gregorovae is reminiscent of the Tortonian to Pliocene Mediterranean Ammotectonica emiliae (Semper, 1861), which is distinguished by its less prominent peripheral cords, the even coarser UC and the distinct groove separating the UC from the base (e.g., Forli et al. 2002: figs 24–26; Chirli 2013: figs 1–6). Discotectonica pseudoperspectiva (Brocchi 1814), from the Pliocene of the Mediterranean Sea, is also somewhat similar but lacks beads, has a much more prominent keel and less prominent UC (e.g., Cavallo & Repetto 1992: fig. 416; Chirli 2013: pl. 3, figs 7–12). The same features allow a separation from the Late Miocene to Pliocene Discotectonica semisquamosa (Bronn, 1831) (e.g., Chirli 2013: pl. 3, figs 13–15).
Paleoenvironment. The occurrence in the Baden Formation suggests middle to outer neritic water depths (Kranner et al. 2021).
Distribution. Known so far only from the middle Badenian (late Langhian) of the Central Paratethys Sea.
Central Paratethys Sea. Middle Miocene (Badenian): Alpine-Carpathian Foreland Basin: Jaroměřice, Lysice, Rudice (Czech Republic) (hoc opus).
description: Published as part of Harzhauser, Mathias & Landau, Bernard, 2023, The Architectonicidae and Mathildidae (Gastropoda, Heterobranchia) of the Miocene Paratethys Sea-victims of the Miocene Climatic Transition, pp. 1-74 in Zootaxa 5370 (1) on page 9, DOI: 10.11646/zootaxa.5370.1.1, http://zenodo.org/record/10147814