Ampezzopleura hybridopsis Nützel, 1998

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 : 161-162

Ampezzopleura hybridopsis Nützel, 1998

Fig. 17A–G .

Material.— One hundred thirty four specimens, 124 from bulk samples, 10 from surface samples; 38 from Lago Antorno ( PZO 12831–12833 , 3 figured specimens; PZO 12830 , 35 specimens); 96 from Misurina Landslide ( PZO 12705– 12708 , 4 figured specimens; PZO 12704 , 92 specimens); Italy, Carnian , Triassic .

Description.—Shell high-spired, slender; largest specimen from Lago Antorno comprises 8–9 whorls, 1.9 mm high, 0.8 mm wide; protoconch 4.5–5 whorls, 0.94 mm high, 0.54 mm wide; protoconch whorls somewhat convex; initial whorls almost flat; remaining larval shell high-spired; first two whorls smooth; remaining larval whorls with strong somewhat opisthocyrt axial ribs numbering 15–20 per whorl; axial ribs rather sharp, much narrower than interspaces between them; larval axial ribs curve strongly forward just above lower suture, becoming thinner at the same time and fusing to a sharp, suprasutural spiral thread which forms angular edge between base and whorl face of larval whorls; base of larval whorls flat to slightly convex; larval ribs do not continue onto base; axial ribs reduced to subsutural row of nodules in last half whorl of larval shell; larval shell ends at wide opisthocyrt arc which is poorly demarcated and not strengthened by a varix; teleoconch whorls slightly convex with broad, wave-like axial ribs numbering about ten per whorl; sutures distinct; base rather flat to slightly convex, joining whorl face at an angle; ribs do not continue onto base; base flat to slightly convex; base and whorls face meet at rounded edge.

Remarks.—The specimens at hand are very close to the type material from Campo near Cortina (type locality) and Alpe di Specie as illustrated and described in Nützel (1998). The reduction of the larval ribs on the last larval whorl to a subsutural row of nodules was interpreted by Nützel (1998) as evidence for a close phylogenetic relationship between Ampezzopleurinae (with axial ribs on larval shell) and Zygopleuridae with a subsutural row of nodules or riblets on larval whorls.

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

Figures

Fig. 17. Zygopleurid gastropods from Lago Antorno (A–C) and Misurina Landslide (D–H), northern Italy, Cassian Formation, Carnian, Upper Triassic. A. Ampezzopleura hybridopsis Nützel, 1998, PZO 12831, axially ribbed larval shell and 3 teleoconch whorls, in lateral view.B. Ampezzopleura hybridopsis Nützel, 1998, PZO 12832, axially ribbed larval shell and 1 teleoconch whorl, in lateral view (B1), B2, last whorl axial ribs reduced to subsutural nodes, in lateral view; B3, earliest whorls smooth, then strong axial ribs,in lateral view.C. Ampezzopleura hybridopsis Nützel,1998, PZO 12833, axially ribbed larval shell.D. Ampezzopleura hybridopsis Nützel, 1998, PZO 12705, axially ribbed larval shell and 2 teleoconch whorls, in apertural (D1), lateral (D2), and apical D3) views. E. Ampezzopleura hybridopsis Nützel, 1998, PZO 12706, teleoconch. F. Ampezzopleurahybridopsis Nützel, 1998, PZO 12707, axially ribbed larval shell and 3 teleoconch whorls, in lateral view (F1), F2, protoconch in lateral view, axial ribs of larval shell reduced to subsutural nodes on last whorl; F3, protoconch in lateral view, axial ribs of larval shell reduced to subsutural nodes and teleoconch ribs begin to appaer on last whorl. G. Ampezzopleura hybridopsis Nützel, 1998, PZO 12708, axially ribbed larval shell and 4 teleoconch whorls, in lateral view. H. Ampezzopleura bandeli Nützel, 1998, PZO 12703, protoconch and ca. 4 teleoconch whorls.