Ampezzogyra angulata Nützel and Hausmann, 2021

Hausmann, Imelda M., Nützel, Alexander, Roden, Vanessa Julie & Reich, Mike, 2021, Palaeoecology of tropical marine invertebrate assemblages from the Late Triassic of Misurina, Dolomites, Italy, Acta Palaeontologica Polonica 66 (1), pp. 143-192 : 168-171

Ampezzogyra angulata Nützel and Hausmann sp. nov.

Fig. 24 .

ZooBank LSID: urn:lsid:zoobank.org:act:3DC97C77-0812-4E8B-91E6-AF5F4445F06D

Etymology: In reference to the angulated whorl profile.

Type material: Holotype ( PZO 12847 ), paratypes ( PZO 12733 , 12734 , 12848 ); four well-preserved specimens with preserved protoconchs . Holotype and paratype PZO 12848 from Lago Antorno, other paratypes from Misurina Landslide .

Type locality: Lago Antorno , near Cortina d’Ampezzo , northern Italy .

Type horizon: Cassian Formation ; lower Carnian, Upper Triassic .

Material.— Twenty three specimens, all from bulk samples; 9 from Lago Antorno ( PZO 12847 , holotype; PZO 12848 , paratype; PZO 12846 , 7 specimens); 14 from Misurina Landslide ( PZO 12733 , 12734 , paratypes; PZO 12732 , 12 specimens); Italy, Carnian , Triassic .

Description.—Shell planispiral with somewhat depressed upper side (assuming dextral teleoconch) and somewhat deeper, widely phaneromphalous umbilicus; shell with about 3.4 whorls, 0.9 mm wide, 0.3 mm high; protoconch flat, comprising about 1.5 whorls, diameter 0.16–0.18 mm; initial whorls dipping, sinistral; protoconch smooth, with convex whorls; protoconch demarcated from teleoconch by a distinct suture and a bulge; teleoconch whorls convex at periphery, ornamented with seven to eight distinct spiral ribs which angulate the whorls somewhat especially at transition from periphery to upper side; axial ribs having character of strengthened growth lines; intersections of weak axial ribs and upper spiral rib somewhat pronounced, node-like, especially in early portions of teleoconch; teleoconch covered with micro-ornament of fine tubercles; shell structure crossed lamellar.

merous spiral threads at which the whorls are not angulated so that the whorls are circular in transverse section. Moreover, the larval whorls have axial folds in A. schroederi while those of A. angulata are entirely smooth. Sloeudaronia karavankensis Kaim, Jurkovšek, and Kolar-Jurkovšek, 2006 , from the Carnian of Slovenia is similar but has widely spaced distinct axial ribs and fewer, more distinct spiral ribs on the whorls. Kaim et al. (2006) placed Sloeudaronia in Vetigastropoda based on the poorly preserved protoconch which they interpreted consisting of one whorl and as being of the vetigastropod type. However, if this protoconch turns out to be heterostrophic, Sloeudaronia and Ampezzogyra could be considered synonyms. The Rinaldoconchus Bandel, 1996 , from the Cassian Formation ( R. bieleri and R. ampezzanus ) is similar but has an elevated spire.

Stratigraphic and geographic range.—Only known from the Carnian, Upper Triassic; northern Italy (Cassian Formation).

Family Tubiferidae Cossmann, 1895

Genus Sinuarbullina Gründel, 1997b

Type species: Sinuarbullina ansorgi Gründel, 1997b ; Poland, Middle Jurassic.

Sinuarbullina sp. 1

Fig. 25A, D .

Material.— Twenty four specimens, all from bulk samples; 10 from Lago Antorno ( PZO 12850 , 1 figured specimen; PZO 12849 , 9 specimens); 14 from Misurina Landslide ( PZO 12736 , figured specimen; PZO 12735 , 13 specimens); Italy, Carnian , Triassic .

Description.—Shell slender, fusiform with last whorl larger than spire, embracing above mid-whorl; illustrated specimens with about 2.5 teleoconch whorls; whorls smooth, evenly convex with narrow subsutural ramp which is demarcated from outer whorl face by an angular edge and a weak spiral furrow; aperture elongated, much higher than wide, narrow posteriorly, wide and rounded anteriorly; protoconch heterostrophic sinistral, transaxial, consisting of about two smooth whorls, 0.28 mm wide ( Fig. 25A ); illustrated specimen from Lago Antorno ( Fig. 25A ) 0.7 mm wide, 1.2 mm high; illustrated specimen from Misurina Landslide ( Fig. 25D ) 0.5 mm wide, 0.9 mm high.

Remarks.— Ampezzogyra angulata sp. nov. resembles the type species A. schroederi Bandel, 1996 . However, A. schroederi has strong axial ribs and only subordinate, weak nu- Remarks.—This is a typical representative of the informal group of “shelled opisthobranchs” which occurs in the Early Triassic ( Batten and Stokes 1986; Nützel 2005; Nützel and Schulbert 2005; Foster et al. 2017) and ranges into the Cretaceous ( Kaim 2004).

Sinuarbullina sp. 2

Fig. 25E .

Material.— Four specimens, all from bulk samples; 2 from Lago Antorno ( PZO 12851 , 2 specimens); 2 from Misurina Landslide ( PZO 12738 , 1 figured specimen; PZO 12737 , 1 specimen); Italy, Carnian , Triassic .

Description.—Illustrated specimen PZO 12738 from Misurina Landslide, 0.5 mm wide, 0.9 mm high.

Remarks.— Sinuarbullina sp. 2 differs from Sinuarbullina sp. 1 by having a lower spire. The protoconch size of both species is more or less the same.

Figures

Fig. 24. Stuoraxid gastropod Ampezzogyra angulata Nützel and Hausmann sp. nov. from Lago Antorno (A, C) and Misurina Landslide (B, D), Cassian Formation, northern Italy, Late Triassic. A. Paratype PZO 12848, in oblique lateral (A1), apical (A2), and apertural (A3) views; A4, detail teleoconch at adapical whorl angulation with micro-ornament of fine tubercles;A5, protoconch in oblique lateral view;A6, protoconch in apical view;A7, crossed lamellar shell structure.B. Paratype PZO 12733, in oblique lateral (B1), apical (B2), and apertural (B3) views. C. Holotype PZO 12847, in apical (C1), basal (C2), and apertural (C3) views; C4, detail of C3; C5, detail teleoconch with micro-ornament of fine tubercles; C6, protoconch in apical view; C7, protoconch in oblique view. D. Paratype PZO 12734, in apical (D1) and apertural (D2) views.

Fig. 25. Heterobranch gastropods from Lago Antorno (A–C) and from Misurina Landslide (D, E), northern Italy, Cassian Formation, Carnian, Upper Triassic. A. Sinuarbullina sp. 1, PZO 12850, in apertural view. B. Sinuarbullina sp. 3, PZO 12852, in lateral view. C. Sinuarbullina sp. 3, PZO 12853, in lateral view. D. Sinuarbullina sp. 1, PZO 12736, in apertural view. E. Sinuarbullina sp. 2, PZO 12738, in lateral view.