Helminthia striatellata ( Sacco, 1895 )

Harzhauser, Mathias & Landau, Bernard, 2019, Turritellidae (Gastropoda) of the Miocene Paratethys Sea with considerations about turritellid genera, Zootaxa 4681 (1), pp. 1-136 : 48-49

Helminthia striatellata ( Sacco, 1895)

Figs 6 Ah, 15A, 15B, 15C, 15D, 15E 1 –E 2

* Haustator striatellatus Sacc. — Sacco, 1895: 16, pl. 1, figs 59a–59b.

Turritella (Haustator) striatellata Sacco — Boettger, 1907: 167.

Turritella (Haustator) sulcomarginalis Sacco — Csepreghy-Meznerics, 1956: 383, pl. 2, figs 34–35 [non Oligodia sulcomarginalis Sacco, 1895 )].

Turritella vermicularis sulcomarginalis Sacco, 1895 — Strausz, 1966: 95, pl. 3, fig. 12 [non Oligodia sulcomarginalis Sacco, 1895 )].

Turritella (H.) striatellata Sacco — Stancu & Andreescu, 1968: plate captions, pl. 3, fig. 27.

Haustator striatellatus Sacco, 1895 — Ferrero-Mortara et al., 1984: 231, pl. 41, figs 1a–1b.

non Turritella (Haustator) cf. striatellata Sacco, 1895 — Bałuk, 1975: 108, pl. 12, fig. 13.

non Turritella (Haustator) striatellatus— İslamoğlu, 2004: 144, pl. 1, fig. 5.

Type material. The syntypes are stored in the Museo Regionale di Scienze Naturali, Torino; BS.061.04.006 ( Sacco 1895, pl. 1, fig. 59a), erroneously listed as holotype by Ferrero-Mortara et al. 1984; BS.061.04.007 ( Sacco 1895, pl. 1, fig. 59b), erroneously listed as paratype by Ferrero-Mortara et al. 1984. To clarify the status of this species we designate specimen BS.061.04.006 as lectotype of Haustator striatellatus Sacco, 1895 . No type locality was mentioned by Sacco (1895), who just stated ‘rare in the Torino Hills’ ( Italy). Most localities in the Torino Hills are of early Miocene age ( Zunino & Pavia 2009).

Studied material. 1 spec. NHMW 2018/0300/0001, 1 spec. NHMW 2018/0300/0002, 1 spec. NHMW 2018/0300/0003, 1 spec. NHMW 2018/0300/0004,1 spec. 2018/0300/0005, 3 spec, 2018/0300/0006; all Letkés ( Hungary) .

Illustrated material. Fig. 15A : NHMW 2018/0300/0001: SL: 42.8 mm, MD: 11.2 mm; Fig. 15B : NHMW 2018/0300/0002, SL: 44.9 mm, MD: 12.4 mm; Fig. 22C : NHMW 2018/0300/0003, SL: 36.7 mm, MD: 10.3 mm; Fig. 15D : NHMW 2018/0300/0004, SL: 24.1 mm, MD: 7.3 mm; all Letkés ( Hungary); Figs 15E 1 –E 2 : SL: 40.5 mm, MD: 11.9 mm; BS.061.04.006, syntype, illustrated in Sacco (1895, pl. 1, fig. 59a), Torino Hills ( Italy).

Revised description. Shell small, slender of about 16 teleoconch whorls. Protoconch unknown. Earliest preserved neanic whorls tricostate with weak s spiral cord; convex, periphery coinciding with B spiral cord. Suture moderately incised. Subsequently numerous secondary spiral cords intercalated. A spiral cord weakening, partly fully replaced by secondary cords, rarely forming weak cord on late neanic whorls. B and C spiral cords more prominent, covered by secondary cords. Post-neanic whorls weakly convex with indistinct suture resulting in stocky appearance of teleoconch whorls, despite the elongate shape. Periphery of whorls below mid-whorl. Shell surface nearly smooth aside from numerous delicate spiral cords with flat tops and narrow interspaces. Faint swelling appears on last and penultimate whorls, equaling C spiral cord in position. Last whorl growth somewhat allometrically, wider and more convex than spire whorls. Lateral sinus with moderately steep angle, ranging around 12.5°; shallow, wide with faint adapical and abapical inflection points; adapical LS p. Basal sinus indistinct, probably weakly opisthocyrt. Base moderately convex covered by 3 to 4 prominent spiral cords with convex tops separated by broader interspaces with up to six secondary spiral cords. Parietal callus thin, glossy, not expanding, tracing primary cords on surface. Aperture subquadrate.

Shell measurements and ratios. No complete specimen available; largest nearly complete specimen: SL: 44.9 mm, MD: 12.4 mm. AA (n=5): μ = 20.0° (σ = 1.0°), PA: μ = 12.0° (σ = 1.2°). Lateral sinus (n = 6): LS angle = 12.5° (σ = 3.4°), LS p = 0.7 (σ = 0.1), LS d = 8.2 (σ = 1.3).

Discussion. This species is characterized by its delicate secondary spiral cords and the strongly suppressed primary sculpture; moreover, the prominent spiral cords on the base are a striking contrast to the delicate sculpture of the whorls. This species was partly mistaken for Oligodia sulcomarginalis ( Sacco, 1895) by Csepreghy-Meznerics (1956) and Strausz (1966) but differs from that species in its convex whorls and lack of a mid-whorl angulation. The specimen from the early Miocene of Turkey identified as Turritella (Haustator) striatellatus by İslamoğlu (2004) has a high last whorl and shows a distinct angulation of the teleoconch whorls; it is almost certainly not conspecific with the Italian type. Similarly, the prominent spiral sculpture and flat whorls of the specimen from the middle Miocene of Korytnica ( Poland), described by Bałuk (1975), has little in common with H. striatellata .

The generic placement in Helminthia is tentative. No information on the order of appearance of the primaries is available. The neanic whorls are reminiscent of those of H. tricincta ( Borson, 1821) , and the three characteristic primary spiral cords of Helminthia are at least faintly present during early stages of growth. The spiral sculpture of the base is also close to that seen in Helminthia species. Thus, H. striatellata seems to be an extreme morph of this genus, characterized by suppressed primaries. A placement in Haustator de Montfort, 1810 , as proposed by Sacco (1895) is unlikely in respect to the shallow, rather simple lateral sinus.

Paleoenvironment. The Letkés locality includes a mixed assemblage of partly reworked taxa ( Kovács & Vicián 2013); the frequent occurrence of corals suggests a shallow marine depositional environment.

Distribution. Central Paratethys. Badenian (middle Miocene): Pannonian Basin: Szob, Letkés ( Hungary) ( Csepreghy-Meznerics 1956; herein); Caransebesulu Basin: Rugi, Delineşti ( Romania) ( Stancu & Andreescu 1968). H. striatellata is a rare species in the Central Paratethys; most specimens were found so far at the Hungarian locality Letkés. The documented distribution might point to a paleogeographic restriction to the southern Paratethyan basins and a stratigraphic restriction to the Langhian equivalent of the Badenian. Proto-Mediterranean Sea. Burdigalian (early Miocene): Torino Hills ( Sacco 1895).

Figures

FIGURE 1. Paleogeography of the Paratethys during the early Miocene (Burdigalian, Eggenburgian, Sakaraulian) and the middle Miocene (Langhian, Badenian, Tarkhanian) (modified after Popov et al. 2004 and Neubauer et al. 2015).

FIGURE 2. Miocene chronostratigraphy after Gradstein et al. (2012) with regional Paratethys stages after Popov et al. (2004) and Piller et al. (2007).

FIGURE 6. Growth line traces of Turritellidae species based on own data; bold: type species of genera; black: Paratethyan species; asterisk: non-Paratethyan species (unknown basal sinuses are left blank).

FIGURE 15. Helminthia striatellata (Sacco, 1895).A. NHMW2018/0300/0001, Letkés(Hungary).B. NHMW 2018/0300/0002, Letkés (Hungary). C. NHMW 2018/0300/0003, Letkés (Hungary). D. NHMW 2018/0300/0004, Letkés (Hungary). E1–E2. Syntype, Torino Hills (Italy), BS.061.04.006.

FIGURE 22. A–D. Zaria aquitanica (Tournouër, 1874). A1–A2. Gamlitz (Austria), NHMW 2018/0170/0001. B1–2. Gamlitz (Austria), NHMW 1868/0001/0370. C. St. Florian (Austria), NHMW 2018/0171/0001. D. 2018/0297/0001, Várpalota (Hungary).