Diarthema aspera Gründel & Nützel, 2024, sp. nov.
Creators: name: Gründel, Joachim
name: Nützel, Alexander
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Littorinimorpha
Aporrhaidae
Diarthema
Diarthema aspera

description: Diarthema aspera sp. nov.
Plate 10: fig. 16, Plate 11: figs 1–4
2019 – Diarthema sp. 1 – Gründel, Keupp and Lang: 137, pl. 10, figs 6–7.
Etymology.
Latin aspera – rough; because of the strong ornamentation.
Holotype.
SNSB-BSPG 2016 XXI 1863.
Paratypes.
7 specimens, SNSB-BSPG 2016 XXI 1862, 1864–1869 and a cast of an imprint (imprint not hand), SNSB-BSPG 2016 XXI 1870.
Type locality and stratum.
Upper Jurassic (Kimmeridgian) reefal limestones from the locality Saal near Kelheim, Lower Bavaria (Gründel et al. 2015, 2022).
Diagnosis.
Spire whorls have a knobby angulation, axial ribs and a strong spiral cord between angulation and abapical suture; last whorl of adult specimens with two wing-like, broadened varices; wings semicircular, with 6–7 strong spiral cords forming node-like projections on outer edge wing; aperture with long vertical rostrum long.
Description.
Shell with high, gradate spire and large, widened body whorl; largest specimen 45 mm high; shell slender consisting of numerous convex whorls; spire whorls angulated at mid-whorl face; suture distinct; oblique ramp demarcated by angulation; whorl face below angulation almost vertical; a weak spiral cord above angulation appears after several whorls; another spiral cord becomes visible above suture; ca. 7 strong axial ribs per whorl; axial ribs do not continue onto base in body whorl of fully grown specimens; intersections of angulation and axial ribs with strong nodes; weaker nodes at intersection abapical spiral cord; some axial ribs thickened varix-like; body-whorl of adults have strongly convex base; transition from whorl face to base evenly rounded; axial ribs disappear; former edge covered with small nodes; base with 4 strong spiral cords with fine nodes; two wing-like widened varices concave in apertural direction; outer lip of aperture widened into a semicircular wing; 6–7 strong spiral cords on the wing and several weak ones between strong cords; strong spiral cords form node-like projections on outer edge of the wing; uppermost strong spiral cord terminated in a spine pointing obliquely in apertural and adapical direction; long, vertically downward (abapical) pointing rostrum, covered with several weak spiral cords.
Remarks.
Gründel et al. (2019, p. 138, as Diarthema sp. 1) reported a vertically upward directed shell-process attached on the penultimate for this species. This shell-process cannot be recognized in the present material. We assume that this is a silicified artifact that does not belong to the shell.
The similar Diempterus? multicostatus Gründel et al. 2022 has more numerous spiral cords of varying strength (but generally weaker than in the present species), the varices on the last whorl have 3 spine-like elongated tubercles. A wing is unknown for Diempterus? multicostatus. Rostellaria benoisti Guirand & Ogérien, 1865 (= Diarthema benoisti sensu Loriol in Loriol and Bourgeat 1886–1888) has numerous reinforced spiral cords on the wing, the wing is asymmetrical with a protruding abapical part. Cyphosolenus tetracer d’Orbigny sensu Loriol in Loriol and Bourgeat (1886–1888) has only 3 strong and numerous weaker spiral cords on the body whorl, the wing extends to the last spire whorl, the spire whorls lack the second strong spiral cord between angulation and abapical suture. Pterocera thurmanni sensu Thurmann and Étallon (1861–1864) as well as Pterocera ponti (Brongniart) sensu Loriol et al. (1872) and Pterocera polypoda Buvignier sensu Loriol in Loriol and Pellat (1874) have a similar wing, but a stouter shell with convex spire whorls, but lacks axial ribs and nodes on spire whorls.
description: Published as part of Gründel, Joachim & Nützel, Alexander, 2024, Late Jurassic (Upper Kimmeridgian) gastropods from Saal near Kelheim (Germany, Bavaria), pp. 19-72 in Zitteliana 98 on pages 19-72, DOI: 10.3897/zitteliana.98.e138605