Coelostylina conica ( Münster, 1841 )

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 : 153-155

Coelostylina conica ( Münster, 1841)

Figs. 10 , 11 .

1841 Melania conica n. sp.; Münster 1841: 28, pl. 23: 20.

1894 Coelostylina conica ( Münster, 1841) ; Kittl 1894: 181, pl. 14: 1–7. 1959 Coelostylina conica ( Münster, 1841) ; Leonardi and Fiscon 1959: 54, pl. 5: 20.

1978 Coelostylina conica ( Münster, 1841) ; Zardini 1978: 44–45, pl. 28: 12–14, pl. 29: 1–3.

pars 1992 Coelostylina conica ( Münster, 1841) ; Bandel 1992: 55, pl. 6: 6, pl. 7: 1, 2, 6, non 5

non 2006, pl. 12: 10–12.

1996 Carboninia valvatiformis n. sp.; Bandel 1996: 55, figs. 17a–h, 18a.

Lectotype: SNSB-BSPG AS VII 504 , the specimen illustrated by Münster (1841: pl. 23: 20).

Type locality: Area near St. Cassian, northern Italy.

Type horizon: Cassian Formation, Late Triassic; Early Carnian.

Material.— One hundred and twenty seven specimens, 82 from bulk samples, 45 from surface samples; 55 from Lago Antorno ( PZO 12803–12810 , 8 figured specimens; PZO 12803 , 47 specimens); 72 from Misurina Landslide ( PZO 12686–12690 , 5 figured specimens; PZO 12685 , 67 specimens); Italy, Carnian , Triassic .

Description.—Shell acutely conical; apical angle about 45°; lectotype comprises about eight whorls, 13.4 mm high, 6.7 mm wide ( Fig. 10A ); last whorl higher than spire; whorls moderately convex with narrow shoulder; sutures distinctly impressed; whorls smooth or with rows of minute pits (seen on lectotype) or very faint spiral grooves which are only visible in oblique light; growth lines slightly opisthocyrt to orthocline; base convex, not demarcated from whorls face; base minutely phaneromphalous; aperture higher than wide, with straight columellar lip and convex outer lip; protoconch conical, more low-spired than teleoconch, apical angle 70–80°; protoconch orthostrophic, smooth, consisting of about 3.5 whorls 0.35–0.45 mm high, 0.38–0.50 mm wide; protoconch whorls convex, without shoulder (in contrast to teleoconch); protoconch demarcated from teleoconch by opisthocyrt ledge; initial whorl flattened, almost planispiral to immersed, with diameter of 0.11–0.13 mm.

Remarks.—The present material from Lago Antorno and Misurina Landslide closely resembles Münster’s (1841) type specimen (lectotype) from the Stuores Wiesen and is obviously conspecific with it. The specimens illustrated by Bandel (1992: pl. 6: 6, pl. 7: 1, 2, 6) also agree well with the present material. However, the protoconchs illustrated by Bandel (1992: pl. 7: 5; 2006: pl. 12: 10–12) and assigned by him to C. conica differ significantly from the protoconchs reported here. According to Bandel’s (1992) illustration and description, the protoconch of Coelostylina conica is about 0.25 mm high and wide, consists of about 2.5 whorls, and has an ornament of minute tubercles. In contrast, the protoconchs reported here consist of 3.5 whorls, are much larger (twice the size) and lack any ornament. The juvenile specimens identified by Bandel (2006: pl. 12: 10–12) have a larval shell with numerous spirally arranges tubercles. This specimen which has only one teleoconch whorl preserved does not represent C. conica but another species and genus. Carboninia valvatiformis Bandel, 1996 , type species of Carboninia Bandel, 1996 , is conspecific with our material and hence represents a synonym of Coelostylina conica and therefore Carboninia is a synonym of Coelostylina . Bandel (1996) interpreted the immersed initial whorl to represent larval heterostrophy with a protoconch of 1.8 whorls but our better preserved material shows that this species has a caenogastropod larval shell of 3.5 whorls which can also be seen in Bandel’s (1996: fig. 17e) illustration of Carboninia valvatiformis .

Stratigraphic and geographic range.—Middle–Upper Triassic, Anisian–Norian/Rhaetian; Italy (southern Alps, Cassian Formation, Raibler Schichten, Marmolata Limestone, Esino Limestone; Latemar Limestone near Forno, Italy, Apennines, Sicily); Italy (eastern and northern Alps, Hauptdolomit); Bulgaria; Hungary; Poland (Silesia, Upper Wellenkalk); Romania (western Carpathians, Siebenbürgen); Iran (Nayband Formation) ( Diener 1926; Kutassy 1940; Sachariewa-Kowatschewa 1962; Kollarova-Andrusova and Kochanova 1973; Nützel and Senowbari-Daryan 1999; Nützel et al. 2012).

Figures

Fig. 10. Coelostylinid gastropod Coelostylina conica (Münster, 1841) from Lago Antorno (A–D) and Misurina Landslide (E, F), northern Italy, Cassian Formation, Carnian, Late Triassic. A. PZO 12803, in apertural (A1) and abapertural (A2) views; A3, spire whorls in lateral view; A4, close up of spire whorl showing faint spirally arranged micro-pits; A5, close up of apical whorls in lateral view. B. PZO 12804 in apertural view. C. PZO 12805, with drill hole, in apertural view (C1); C2, early whorls including protoconch, in lateral view. D. PZO 12806, in lateral view (D1); D2, early whorls including protoconch, in lateral view; D3, whorl detail with boring.E. PZO 12686, in apertural view. F. PZO 12687, with drill hole in apertural view (F1); F2, detail, in apertural view.

Fig. 11. Coelostylinid gastropods Coelostylina conica (Münster, 1841) from Lago Antorno (A–D) and Misurina Landslide (E–G), northern Italy, Cassian Formation, Carnian, Upper Triassic. A. PZO 12807, A1, teleoconch shows faint spiral furrows in oblique apical view; A2, apertural view; A3, protoconch in lateral view with sinusigera. B. PZO 12808, in apertural view, with drill hole. C. PZO 12809, C1, juvenile whorls including protoconch ending at sinusigera, in oblique lateral view; C2, juvenile whorls including protoconch ending at sinusigera, in apertural view. D. PZO 12810, teleoconch shows faint spiral furrows, end of smooth larval shell well visible, in oblique apical view. E. PZO 12688, in lateral view. F. PZO 12689, F1, juvenile whorls including protoconch in apical view; F2, juvenile whorls including protoconch, in lateral view; F3, juvenile whorls including protoconch, in lateral view; F4, juvenile whorls including protoconch with dipping initial whorl, in lateral view. G. PZO 12690, juvenile whorls including protoconch, in lateral view.