Pleurotomaria sp. 2

Szabó, János, 2017, Gastropods of the Lower Jurassic Hierlatz Limestone Formation, part 3. New pleurotomarioideans from the fauna of Hierlatz Alpe (Hallstatt, Austria), Fragmenta Palaeontologica Hungarica 34, pp. 9-48 : 28-30

Pleurotomaria sp. 2

( Figs 91–96 )

Material – Single, poorly preserved specimen (GBA 2018/002/0008) with two, fragmentary, strongly recrystallized whorls, showing enough morphological details to distinguish it from the other species.

Measurements – Height of the specimen: 22.6 mm.

Description – The specimen represents the penultimate and the last whorl of a conoidal shell, having about 40–45° coiling angle. From the fragments, rather high whorls can be reconstructed. The whorls are of Pleurotomaria type but have only an extremely narrow subsutural ramp, at the same time, the suture is deeply impressed, therefore the gradate outline of the shell has developed indistinctly. The outer face is wide and steep with the selenizone at the midwhorl; a wide concave belt is between the ramp angle and the selenizone but more or less concave interspaces separate also the spiral ornamental elements.

The description of the ornament can be given almost exclusively from the last whorl. Its sculpture is composed of few but robust components; sparse, elongated, collabral elevations are on both sides of the selenizone. On the ramp, these rib-like elevations start at the suture and reach their maximum height at the angulation where they cross a rather wide spiral ribbon then vanish in direction of the selenizone within the widest concave belt of the outer face. The selenizone runs between two obscure striae and bears a marked spiral cord in its midline. Below the selenizone, the onsets of the collabral elevations are quite near to the selenizone and they terminate in the outermost belt of the base; a few wide spiral ribbon cross them with node-like peaks. Four of such ribbons are visible on the available specimen but one belongs already to the base.

Remarks – The specimen is somewhat similar to the photos of SACCHI VIALLI (1964), named as Pleurotomaria hettangensis Terquem, 1855 (Plate 1: 7–9). This name is applied instead of Pleurotomaria oblita Parona, 1893 and Pleurotomaria granulatocincta Parona, 1893 that do not belong to P. hettangensis by MONARI et al. (2011, p. 365) opinion. Both species belong to that group of conoidal forms in Pleurotomaria , which have narrow ramp and barely or not gradate outline. Both differ from Pleurotomaria sp. 2 in the more marked nature of the differently arranged spiral ornamental elements that are cords and carinae, not flat ribbons.

Distribution – Within Sinemurian to lowermost Pliensbachian (Lower Jurassic) part of the Hierlatz Limestone Formation in Hierlatz Alpe, Hallstatt, Austria.

Figures

Figs 85–96. Pleurotomaria sp. 1 and Pleurotomaria sp. 2, new species for the Hierlatz Alpe fauna but are either unidentifiable or notsuitable to outline new species owing to their poor preservation. – 85–90. Pleurotomaria sp.1 (GBA 2018/002/0007). – 85–86. Lateral view (×3 and ×1). – 87–88. Basal view (×3 and ×1). – 89–90. Lateral view (×3 and ×1). – 91–96. Pleurotomaria sp. 2 (GBA 2018/002/0008). – 91–92. Lateral view (×3 and ×1). – 93–94. Apical view (×3 and ×1). – 95–96. Basal view (×3 and ×1)