Nipteraxis deformatus Harzhauser & Landau 2023, nov. sp.
Creators: name: Harzhauser, Mathias
name: Landau, Bernard
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Heterostropha
Architectonicidae
Nipteraxis
Nipteraxis deformatus

description: Nipteraxis deformatus nov. sp.
Figs 4E, 16A–D
Type material. Holotype: NHMW 2012 /0229/0049a, SL: 9.5 mm, MD: 15.9 mm, Traiskirchen (Austria), Figs 16A 1 –A 3. Paratypes: NHMW 2010 /0004/0456a, SL: 8.1 mm, MD: 14.1 mm, Bad Vöslau (Austria), Figs 4E, 16B 1 –B 3. NHMW 2010 /0004/0456b, SL: 7.0 mm, MD: 13.0 mm, Bad Vöslau (Austria), Figs 16C 1 –C 3. NHMW 2010 /0004/0456c, SL: 7.4 mm, MD: 13.2 mm, Bad Pfaffstätten (Austria), Figs 16D 1 –D 3. 2 spec. NHMW 2012 /00213/0035, Pfaffstätten (Austria).
Type locality. Traiskirchen (Austria), Vienna Basin.
Type stratum. Silty sand of the Baden Formation.
Age. Middle Miocene, early/middle Badenian (Langhian).
Etymology. Referring to the slightly deformed whorls with slight swellings and bumps.
Diagnosis. Large, relatively high conical, weakly carinate species with moderately prominent finely beaded spiral sculpture on dorsum, weak spiral sculpture on base and small indistinct UC. Whorls with poorly defined prosocline swollen portions followed by smoother areas, interpreted as growth halts.
Description. Shell large, with relatively high, conical spire, periphery weakly carinate. Protoconch heterostrophic, medium-sized of 1.2 visible convex whorl (diameter 1.1 mm). Teleoconch of about four whorls. First teleoconch whorl convex with beaded LPC and UPC and prosocline axial ribs. Later whorls with more prominent SSC with larger, subquadratic to rectangular beads. Two or three weaker, beaded MCs and more prominent UPC and LPC. SSC and MCs close spaced; peripheral cords separated by wider interspace, occasionally bearing delicate, beaded spiral thread intercalated. Strength of spiral cords and beads rather uniform on penultimate whorl. Beads fading on last whorl. Periphery formed by prominent, convex LPC and slightly weaker, beaded IPC. Base moderately convex. Basal field with three broad, flat spiral cords separated by shallow spiral grooves with delicate spiral threads superimposed. Entire base with distinct growth lines delimiting vague axially elongated rugae. PUC broad with small, dense axials folds, separated by narrow groove from moderately prominent UC, overhanging umbilicus. Umbilicus cylindrical, moderately wide (~23% of total diameter). Especially last whorl characterized by poorly defined prosocline swollen portions followed by smoother areas, interpreted as growth halts. Aperture subcircular with narrow CG. PG absent.
Discussion. Nipteraxis exmoniliferus (Sacco, 1892) is reminiscent of N. deformatus and both species have been mixed in the NHMW collections. They are distinguished by the much stronger beads on the dorsal side of the much smaller N. exmoniliferus and its more prominent UC. Shells of N. exmoniliferus could be mistaken for juveniles of N. deformatus but differ in their coarser and more rounded beads on the first two teleoconch whorls. In addition, N. exmoniliferus seems to have preferred inner neritic environments whereas N. deformatus was a deeper water species.
This species is reminiscent of an extant species group, which was placed by Bieler (1993) in Solatisonax (S. propinqua Bieler, 1993, S. supraradiata (von Martens, 1904), S. hemisphaerica (Seguenza, 1876), S. radialis (Dall, 1908). As discussed under the genus Solatisonax, we recognize two species groups in the species included in that genus by Bieler (1993). The second group including S. propinqua, S. supraradiata, S. hemisphaerica, and S. radialis is very close in shell characters to what we have included here in Nipteraxis. As discussed above, we use this Eocene genus with some hesitance, and it may be that all these species represent a yet unrecognized genus group. We await molecular data to elucidate the relationships between this group of architectonicids.
Paleoenvironment. The occurrence in the Baden Formation suggests middle to outer neritic water depths (Kranner et al. 2021).
Distribution. Only known from the Langhian equivalent of the Badenian in the Central Paratethys Sea.
Central Paratethys Sea. Badenian (Middle Miocene): Vienna Basin: M̂llersdorf, Pfaffstätten, Traiskirchen (Austria).
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 pages 32-34, DOI: 10.11646/zootaxa.5370.1.1, http://zenodo.org/record/10147814