Naticopsidae Waagen, 1880

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 : 151-153

Family Naticopsidae Waagen, 1880 Genus Hologyra Koken, 1892

Type species: Hologyra alpina Koken, 1892 , subsequent designation by Kittl (1899); northern Italy, Late Triassic.

Hologyra? expansa ( Laube, 1869)

Fig. 7 .

1869 Naticopsis expansa ; Laube 1869: 11, pl. 22: 5.

1892 Naticopsis expansa Laube sp.; Kittl 1892: 82, pl. 7: 22–24. 1978 Hologyra expansa (Laube) ; Zardini 1978: 35, pl. 19: 6–12, 23, 24.

Material.— One specimen ( PZO 12802 ) from Lago Antorno surface sample, Italy, Carnian, Triassic .

Description.—Shell bulbous, consisting of about four rapidly expanding whorls, 3.6 mm wide, 3.9 mm high; spire slightly elevated; whorls markedly convex, with broad subsutural shelf; whorl embracing somewhat above periphery; whorls smooth except for distinct, prosocline, prosocyrt growth lines; aperture with outer lip broken off, with pronounced callus on parietal lip.

Remarks.—This specimen differs from the other neritimorphs in the studied samples, Neritaria mandelslohi and Dentineritaria neritina , by having a low but nevertheless distinctly elevated spire. It is much larger than the specimens representing these species in our samples that are only present with small juveniles. It agrees well with the illustrations of H. expansa given by Kittl (1892) who also figured Laube’s (1869) type specimens. It is also close to the specimens that were illustrated by Zardini (1978) as H. expansa . Species identity is not entirely beyond doubt because this specimen is not fully grown and large parts of the aperture are broken off. The placement of this species in Hologyra is doubtful because the type species of Hologyra has a blunt and not an elevated spire.

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

Family Neritariidae Wenz, 1938

Genus Neritaria Koken, 1892

Type species: Natica mandelslohi Klipstein, 1843 ; Italy, Late Triassic.

Neritaria mandelslohi (Klipstein, 1843)

Fig. 8 .

2007 Neritaria mandelslohi (Klipstein, 1843) ; Bandel 2007: 261, fig. 11N–P, fig. 12A–H.

Material.— Thirty four specimens, all from bulk samples; 29 from Lago Antorno ( PZO 12798 , 12799 , 2 figured specimens; PZO 12797 , 27 specimens); 5 from Misurina Landslide PZO 12681 , 5 specimens); Italy, Carnian , Triassic .

Description.—Shell egg-shaped, low-spired with rapidly increasing whorls; illustrated specimen with about three whorls, 0.7 mm wide and high; initial whorl corroded but seemingly convolute, smooth; larval shell largely smooth, only with faint reticulate ornament on adapical portion of whorls; reticulate ornament consists of somewhat strengthened growth lines and spiral lirae which diverge somewhat in an apertural direction; base smooth, evenly rounded; larval shell with diameter of about 0.5 mm, ends at simple, faint suture; only small part of teleoconch present, seemingly smooth.

Remarks.—Only isolated larval shells or juvenile specimens with a small teleoconch portion are at hand. They do not exceed a size of 1 mm. However, this species reaches a size of several millimetres at other locations ( Kittl 1892; Bandel 2007). This could indicate that the studied specimens represent mortal larval fall (failure to undergo metamorphosis) or that specimens died at or shortly after metamorphosis. The larval shell is rather characteristic and resembles that of Neritaria mandelslohi as reported by Bandel (2007: fig. 11N–P).

Stratigraphic and geographic range.—Ladinian–Carnian, Triassic; Muschelkalk in Poland; northern Italy (Cassian Formation); Hungary ( Diener 1926; Kutassy 1940).

Genus Dentineritaria Bandel, 2007

Type species: Natica neritina Münster, 1841 ; Italy, Late Triassic.

Dentineritaria neritina ( Münster, 1841)

Fig. 9 .

2007 Dentineritaria neritina (Münster) ; Bandel 2007: 265, fig. 13A–H.

Material.— One hundred and six specimens, all from bulk samples; 68 from Lago Antorno ( PZO 12801 , figured specimen; PZO 12800 , 67 specimens); 38 from Misurina Landslide ( PZO 12683 , 12684 , 2 figured specimens; PZO 12682 , 36 specimens); Italy, Carnian , Triassic

Description.—Shell egg-shaped, low-spired with rapidly increasing whorls; illustrated specimen ( Fig. 9A ) with about three whorls, 0.9 mm wide, 0.8 mm high; protoconch consists of about three smooth whorls, 0.43 mm wide; initial whorls corroded but seemingly convolute; last larval whorl with distinct adapical suture; larval shell ends at simple, faint suture; somewhat less than one teleoconch whorl preserved; early teleoconch with subsutural bulge and initially with weak axial ribs (strengthened growth lines) which are restricted to adapical portion of whorls; axial ribs fade after half whorl so that remaining teleoconch is entirely smooth; base smooth, evenly rounded; aperture higher than wide with evenly arched outer lip; inner lip reflexed, forming columellar callus; first illustrated specimen from Misurina Landslide ( Fig. 9B ) is 0.8 mm wide and 0.7 mm high; consists of about three whorls; second specimen ( Fig. 9C ) 0.7 mm wide, with about two whorls; both illustrated specimens from Misurina Landslide less well preserved than illustrated shell from Lago Antorno.

Remarks.—As in Neritaria mandelslohi , only isolated larval shell or specimens with a small teleoconch portion are at hand. Thus even this neritimorph species did not find suitable living conditions in the sampled area. The present specimens resemble early growth stages of Dentinerita neritina as reported by Bandel (2007). Bandel (2007) interpreted the axial ribbed shell as a part of the larval shell which according to him has a diameter of 0.8 mm. However, the present material suggests that the larval shell is much smaller (0.4 mm wide) and that the axially ribbed shell represents the early teleoconch.

Stratigraphic and geographic range.—Ladinian–Carnian, Triassic; Italy (southern Alps, Cassian Formation, Esino Limestone, Marmolata Limestone; eastern Alps, Coquina of Ghegna); South America ( Diener 1926; Kutassy 1940).

Figures

Fig. 7. Naticopsid gastropod Hologyra? expansa (Laube, 1869), PZO 12802, from Lago Antorno, northern Italy, Cassian Formation, Carnian, Upper Triassic; apertural view showing callus on inner and parietal lip.

Fig. 8. Neritariid gastropods Neritaria mandelslohi (Klipstein, 1843) from LagoAntorno, northern Italy, Cassian Formation, Carnian, Upper Triassic. A. PZO 12798, in oblique lateral (A1) and lateral view (A3), and oblique lateral view of protoconch (A2). B. PZO 12799 in apical view.

Fig. 9. Neritariid gastropods Dentineritaria neritina (Münster, 1841) from Lago Antorno (A) and Misurina Landslide (B, C), northern Italy, Cassian Formation, Carnian, Upper Triassic. A. PZO 12801, in apertural (A1) and apical (A2) views; A3, end of smooth larval shell well visible in oblique lateral view. B. PZO 12683, in apertural (B1) and abapertural (B2) views. C. PZO 12684 in apical view.