Thiarella bronni ( Mayer, 1869 ) Harzhauser & Landau, 2021

Harzhauser, Mathias & Landau, Bernard M., 2021, The Columbellidae (Gastropoda, Buccinoidea) in the Miocene Paratethys Sea — striking diversity of a negelected group, Zootaxa 5025 (1), pp. 1-75 : 43-45

Thiarella bronni ( Mayer, 1869) nov. comb.

Figs 4S, 14A 1 –A 2 , B 1 –B 2 , C 1 –C 2

Columbella tiara Bon. —Hörnes 1852: 119, pl. 11, figs 7a–c [non Brocchi, 1814].

Columbella tiara Bon. —Hörnes 1856: 666, pl. 51, figs 2a–b [non Brocchi, 1814].

* C [olumbella]. Bronni— Mayer 1869: 284 [nov. nom. pro Columbella tiara Hörnes 1852 , pl. 11, fig. 7].

Columbella (Nitidella) tiara Brocc. — Hoernes & Auinger 1880: 94, pl. 11, fig. 3 [non Brocchi, 1814].

Scabrella bronni Mayer — Meznerics 1933: 342, pl. 14, figs 3a–b.

Pyrene (Crenisutura) thiara Brocc. — Sieber 1947: 157 [non Brocchi, 1814].

M.[itrella]. (S [cabrella].) bronni (May.) — Sieber 1958a: 147.

Macrurella (Scabrella) bronni (May.) — Sieber 1958b: 148.

Pyrene (Crenisutura) thiara (Brocchi) — Csepreghy-Meznerics 1969: 84, pl. 4, fig. 9 [non Brocchi, 1814].

Type material. Holotype: NHMW1865 /0001/0969 Baden ( Austria), illustrated in Hörnes (1852, pl. 11, figs 7a–c), the specimen is lost.

Illustrated material. NHMW 1855/0045/0045a, SL: 17.8 mm, MD: 5.9 mm, Hlohovec (the Czech Republic), illustrated in Hörnes (1856, pl. 51, figs 2a–b), Figs 14C 1 –C 2 . NHMW 1864/0040/1123a, SL: 17.3 mm, MD: 6.1 mm, Borač (Boratsch) (the Czech Republic), illustrated in Hoernes & Auinger (1880, pl. 11, fig. 3), Figs 14B 1 –B 2 . NHMW 1864/0040/1123b, SL: 18.1 mm, MD: 6.6 mm, Borač (Boratsch) (the Czech Republic), Figs 14A 1 –A 2 .

Additional material. NHMW1887 /0018/0015, SL: 6.1 mm, MD: 2.6 mm, Steinebrunn ( Austria) , illustrated in Meznerics (1933, pl. 14, figs 3a–b), Fig. 4S. NHMW1860 /0001/0133, 2 spec., Hlohovec (the Czech Republic) ; NHMW1864 /0040/1122, 66 spec., Borač (Boratsch) (the Czech Republic) , NHMW1864 /0040/1977, 18 spec., Lomnička u Tišnova (the Czech Republic) ; NHMW1855 /0045/0635, 1 spec. Grund ( Austria) , NHMW 2020 /0169/0001 (ex coll. B. Landau), 2 spec., Szob ( Hungary) .

Revised description. Shell medium sized, moderately broad fusiform, with high conical spire. Protoconch conical of about three smooth, convex whorls. Teleoconch of nine whorls. Spire whorls flat-sided with narrowly incised, weakly undulating suture. Sculpture of widely spaced orthocline to weakly opisthocline axial ribs. Elevated subsutural collar, over which ribs become nodular to slightly spinous, strengthening abapically, making later whorls strongly coronate. Spire outline weakly gradate due to subsutural collar. Last whorl with weak concavity below strongly elevated collar, swollen mid-whorl forming strongly rounded periphery, base weakly convex, rapidly contracting into long siphonal canal. Axial ribs becoming wider spaced and narrower abapically, slightly sinuous on last two whorls. Spiral sculpture of delicate spiral cords appears within 5 th to 6 th teleoconch whorls, strengthening abapically, most prominent over siphonal fasciole. Aperture moderately narrow, elongate ovoid. Outer lip thin with about eight small elongated denticles within. Anal canal narrow, U-shaped. Siphonal canal long, moderately wide, shallowly notched at tip. Columellar callus forming narrow rim, not sharply delimited from base in most specimens, with about five indistinct denticles along columellar edge; denticles absent in many specimens).

Shell measurements and ratios. SL: 17.3–17.8 mm, MD: 5.9–6.6 mm, AA: 32–35°, SL/MD: 2-7–3.0, AL/ AW: 3.6–3.9, LWH/AH: 1.3.

Discussion. Thiarella bronni ( Mayer, 1869) differs most notably from Thiarella thiara ( Brocchi, 1814) in the presence of axial ribs, the rounded, narrowly swollen mid-portion of the last whorl forming the periphery, and the shorter siphonal canal.

Palaeoenvironment. Unknown.

Distribution in Central Paratethys. Badenian (middle Miocene): North Alpine-Carpathian Foredeep: Grund, Windpassing ( Austria) ( Sieber 1947; own data), Borač, Lomnička u Tišnova (the Czech Republic) (own data); Vienna Basin: Bad Vöslau, Baden-Sooss, Steinebrunn ( Austria) ( Hoernes & Auinger 1880; Sieber 1958b), Hlohovec (the Czech Republic) (own data); Eisenstadt-Sopron Basin: Forchtenau ( Austria); Bükk Mountains: Borsodbóta ( Hungary) ( Csepreghy-Meznerics 1969); Făget Basin: Coşteiu de Sus ( Romania) ( Boettger 1906).

Genus Zafrona Iredale, 1916

Type species. Columbella isomella Duclos, 1840 ; original designation by Iredale (1916: 32). Present-day, Indo-Pacific.

Discussion. Iredale (1916; 32) did not provide a detailed diagnosis of the genus but stated that Zafrona species range ‘from very small, 2 mm, to comparatively large, 5 mm, from slender to obese and from closely sculptured to almost smooth’. The type species is characterised by prominent axial ribs crossed by strong spiral cords, resulting in a slightly beaded sculpture. In species such as Zafrona pleuriferoides Monsecour, K. & D. Monsecour, 2018 and Z. azteci Monsecour, K. & D. Monsecour, 2016, the spiral sculpture is rather reduced like in the Paratethyan species. All Zafrona species , however, are characterised by a conical, multispiral protoconch.

Retizafra Hedley, 1914 (type species Pyrene gemmulifera Hedley, 1907 ) is also characterised by prominent axial ribs and strong spiral cords, which are most prominent in the interspaces between the axial ribs; but all Retizafra species develop small paucispiral protoconchs ( Maxwell et al. 2019; Hoffman et al. 2019).

Zafrona sphaerocorrugata is the first record of this genus from the Paratethys Sea. In the northeastern Atlantic, the genus was represented from the middle and late Miocene by Zafrona arpula (Michelotti, 1840) , which persisted in the Mediterranean Sea into the Pliocene ( Landau et al. 2019). Zafrona recticostata (Sacco, 1890) is a second Pliocene Mediterranean species ( Sacco 1890b). In the European fossil literature these species have often been placed in the genus/subgenus Anachis H. & A. Adams, 1853. The type species Anachis scalarina (G.B. Sowerby I, 1832) from the east Pacific has quite a different profile, with a gradate spire, swollen mid-portion to the last whorl, and much stronger flexuous axial ribs. Zafrona species have regularly ovoid to tall-spired shells. We await molecular data to better elucidate the relationship between these genera.

Figures

FIGURE 1. A. Map of central and south–eastern Europe, representing the area that was partly covered by the Central Paratethys Sea. The white insert corresponds to the area that is restored in the palaeogeographic map below. B. Paleogeography of the Middle Miocene Paratethys Sea showing the most important sedimentary basins (NAFB: North Alpine Foreland Basin, E–Sopr B: Eisenstadt–Sopron Basin).

FIGURE 2. Measurements for shell morphology and whorl profiles. SL: shell length, MD: maximum diameter, AA: apical angle, LWH: last whorl height, AH: aperture height. AL: aperture length. AW: aperture width.

FIGURE 14. A1–A2. Thiarella bronni (Mayer, 1869), NHMW1864/0040/1123b, SL: 18.1 mm, MD: 6.6 mm, Borač (Boratsch) (the Czech Republic). B1–B2. Thiarella bronni (Mayer, 1869), NHMW1864/0040/1123a, Borač (Boratsch) (the Czech Republic). C1–C2. Thiarella bronni (Mayer, 1869), NHMW1855/0045/0045a, Hlohovec (the Czech Republic). D1–D2. Zafrona sphaerocorrugata nov. sp., NHMW 1866/0001/0814a, holotype, Niederleis (Austria). E. Zafrona sphaerocorrugata nov. sp., NHMW1866/0001/0814b, paratype, Niederleis (Austria). F1–F2. Zafrona sphaerocorrugata nov. sp., NHMW1866/0001/0814b, paratype, Niederleis (Austria). G1–G2. Scabrella haueri (Hoernes & Auinger, 1880), NHMW1863/0015/0632a, lectotype, Niederleis (Austria). H1–H2. Scabrella haueri (Hoernes & Auinger, 1880), NHMW1863/0015/0632b, paralectotype, Niederleis (Austria). I1–I2. Scabrella haueri (Hoernes & Auinger, 1880), NHMW1863/0015/0632, paralectotype, Niederleis (Austria).