Swantina crassiconvexa, Schallreuter & Hinz-Schallreuter, 2010

Schallreuter, Roger E. L. & Hinz-Schallreuter, Ingelore C. U., 2010, Sexual dimorphism and pore systems in Ordovician ostracodes, Acta Palaeontologica Polonica 55 (4), pp. 741-760 : 754-758

Swantina crassiconvexa sp. nov.

Fig. 4B, C.

1973 Levisulculus sp. n.?; Neben and Krueger 1973: pl. 89: 4.

1975 Levisulculus sp. n.?; Schallreuter 1975: 158–159, pl. 4: 9–12, pl. 8: 12, 13.

1983 Levisulculus sp. n.? sensu Schallreuter (1975); Schallreuter 1983a: 169.

?1992 Swantina aff. swantia ( Schallreuter, 1969) ; Sidaravičienė 1992: 142, 243, pl. 36: 3.

Etymology: After the ventrally strongly convex velum.

Holotype: Female left valve, GG 33−18 (Fig. 4C; Neben and Krueger 1973: pl. 89: 4; Schallreuter 1975: pl. 4: 9–11).

Type locality: Beach of the Dornbusch, the high−lands of the Isle of Hiddensee (Baltic Sea); glacial erratic boulder.

Type horizon: Swedish Backsteinkalk (erratic boulder 1B1), age: like Skagen limestone, lower Upper Ordovician.

Material.—See Schallreuter (1975: table 8).

Fig. 6. Oepikellid ostracods from Palaeozoic erratic boulders. A–F. Swantina serrata Schallreuter, 1986 . A. GG 347−9b, female left valve, L 0.99 mm; lat− H eral view; erratic boulder G−287. B. GG 347−9d, tecnomorphic right valve, L 0.85 mm; lateral view; erratic boulder Sy−2. C. GG 347−9f, female right valve,

L 0.79 mm; lateral view; erratic boulder G−30. D. GG 347−9c, female right valve, L 1.00 mm; ventral view, erratic boulder G−30. E. GG 347−9e, tecnomorphic right valve, L 0.98 mm; lateral view; erratic boulder G−30. F. GG 347− 9g, tecnomorphic left valve; lateral view; erratic boulder Sy−2.

G–L. Swantina pseudobliqua Schallreuter, 1986 . G. GG 347−10a, tecnomorphic right valve, L 0.99 mm; lateral view (ventrolateral view: Fig. 5G); erratic boulder Sy−60. H. GG−347−10c, female right valve, L 0.98 mm; lateral view; erratic boulder Sy−60. I. GG 347−10e, female left valve, L 1.05 mm; lateral view; erratic boulder 791. J. GG 347−10b, female left valve, L 1.00 mm; ventral view; erratic boulder Sy−60. K. GG 347−10d, tecnomorphic left valve,

L 0.72 mm, lateral view; erratic boulder G−287. L. GG 347−10f, anteriorly incomplete young tecnomorphic left valve, L 0.66 mm; lateral view; erratic boul−

der Sy−2. Stereo−pairs. All erratic boulders are of the upper Upper Ordovician Öjlemyr flint and came from the Isle of Gotland, Baltic Sea (G) and the Isle of Sylt, North Sea (Sy). Scale bars 0.3 mm .

doi:10.4202/app.2009.0056

Dimensions and proportions.—See Schallreuter (1975: ta− low centre and not depressed. Velar frill restricted, extending ble 8). from anterocentral to posteroventral region. Terminal velar

Diagnosis (emended).—Adults at least up to 1.17 mm. Out− spine distinct. Tubules of the velar frill densely set and may line distinctly preplete. Very short terminal velar spine in line terminate as short spines. Tubules of the dolon bending with posterior cardinal corner. Dolon strongly convex abruptly in posterior direction in outer part of the frill. Mar−

centroventrally. Antrum terminating very distinctly in the ginal sculpture as a row of spines, at the antrum as a ridge posterior centroventral region. which is broader than in the tecnomorphs. On both side of the antrum small toral ridges function as the antral fences. Lat−

Remarks.—This new species, which may co−occur with S. eral surface with densely set coarse pustulae.

swantia , differs from the latter by its distinctly preplete out−

Comparisons

.—Tecnomorphs of

S. pseudobliqua

are

very line and the velum, which is strongly convex centroventrally. similar to tecnomorphs of the co−occurring Levisulculus obli−

Swantina aff. swantia Sidaravičienė (1992 : pl. 36: 3; L

quus. In general, L. obliquus is more distinctly preplete. Fur−

1.1 mm) from the Johvi Stage of Lithuania may belong to the thermore, the terminal velar spine is located within the velar

new species. flange and thus, slightly more anteriorly. However, in small

Stratigraphic and geographic range.—Until now, known tecnomorphs of L. obliquus the velar frill behind the spine

only from erratic boulders of the younger Swedish Back− may be developed weakly, or may even be missing, which

steinkalk (1B 1 type; Skagen limestone, corresponds to the makes its distintion from S. pseudobliqua problematic. Apart

Keila Stage, D2, of Estonia; Männil 1990: 18), mid−Viru, from that, the velar frill may sometimes terminate anteriorly

lower Upper Ordovician (upper Sandbian/lower Katian). in L. obliquus in a small spine ( Schallreuter 1986: pl. 1: 12).

Swantina pseudobliqua Schallreuter, 1986 Stratigraphic and geographic range.—The species has been

Figs. 4D, 5E–H, 6G–L, 7D. found in several Öjlemyr flint boulders from the Isle of

1986 Swantina pseudobliqua sp. n.; Schallreuter 1986: 9, 16 (1987: Gotland, Baltic Sea (erratic boulders G−2 [9], 791 [4], G−287

209, 216), pl. 1: 11. [3]) and of the Isle of Sylt, North Sea (erratic boulders Sy−2

Holotype: Female left valve, GG 400−3347 ( Schallreuter 1986: pl. 1: [18], Sy−56 [9], Sy−60 [68], Sy−75 [12], Sy−207 [33]).

11). Catalogue of Keyser and Schöning 1996 no. 3467. Swantina serrata Schallreuter, 1986

Type locality: Former gravel pit near Braderup, Isle of Sylt, Germany; Figs. 4E–G, 5M, 6A–F, 7E.

erratic boulder. 1986 Swantina serrata sp. n.; Schallreuter 1986: 9, 16 (1987: 209,

Type horizon: Öjlemyrflint (Braderup type), erratic boulder Sy−207. 216), pl. 1: 10.

Pirgu (F1c) or Porkuni Stage, upper Upper Ordovician. 1992 Swantina cf. serrata Schallreuter, 1986 ; Sidaravičienė 1992: 144,

Material.—More than 100 valves, mostly larvae. 244, table 2, pl. 36: 9.

Dimensions and proportions.—See Table 7. Type material: Holotype: female right valve, lost ( Schallreuter 1986:

pl. 1: 10). Catalogue of Keyser and Schöning 1996 no. 3468. Neotype

Diagnosis (emended).—Females 0.79–1.14 mm (holotype) (designated herein): female left valve GG 347−8 (Fig. 4F).

long. Outline amplete or slightly preplete. Cardinal angles Type locality: Former gravel pit near Braderup, Isle of Sylt, Germany ;

slightly exceeding 90 °. Rounded muscle spot only a little be− erratic boulder.

H

doi:10.4202/app.2009.0056

Type horizon: Öjlemyrflint (Braderup type), erratic boulder Sy 208; Pirgu (F1c) or Porkuni Stage, upper Upper Ordovician .

Material.—More than 100 valves, mostly larvae.

Dimensions and proportions.—See Table 8.

Diagnosis (emended).—Length at least up to 1.06 mm (holotype 1.00 mm, neotype 1.06 mm). Rounded muscle spot in centre, or slightly in front of centre. Velar frill of tecnomorphs distally often developed as a row of short, posteriorly declined spines which may appear serrated. Terminal velar spine short. Outer surface weakly pustulate.

Discussion.— Swantina serrata and Swantina pseudobliqua , which may co−occur, are very similar. S. serrata differs from S. pseudobliqua by the arrangement of the velar spines in tecnomorphs. The spines are less dense in S. serrata and are declined posteriorly. This is often more distinct in smaller tecnomorphs. The terminal velar spine is only weak in S. serrata . The granulation of the lateral surface is generally stronger in S. pseudobliqua .

Stratigraphic and geographic range.— Sidaravičienė (1992: pl. 36: 9) figured the species from the Vormsi stage (F1b) of Lithuania and mentioned the occurrence of the species also in the Rakvere (E), Nabala (F1a), and Pirgu Stages (F1c). The species has been found in several Öjlemyr flint boulders from the Isles of Gotland, Baltic Sea (erratic boulders G−2 [3 valves], G−30 [21], G−287 [1]) and of the Isle of Sylt, North Sea (erratic boulders Sy−2 [12], Sy−56 [3], Sy−60 [33], Sy−61 [4], Sy−75 [23], Sy−207 [26], Sy−208 [4]).