Schizotreta sp. 1

Hansen, Jesper & Holmer, Lars E., 2011, Taxonomy and biostratigraphy of Ordovician brachiopods from northeastern Ny Friesland, Spitsbergen 3076, Zootaxa 3076 (1), pp. 1-122 : 37-39

Schizotreta sp. 1

Pl. 7, Figs. 4 –6

Material. Two dorsal valves from sample JH-170, including the figured specimen, TSGF 17017.

Description. Shell moderately convex and thin-walled. Outline subcircular. One specimen about 0.6 mm long and 0.6 mm wide. Larval shell subcircular, smooth and about 0.38 mm long. Postlarval shell with irregular filae of uneven size, fine radial striation, and micro-pitting in radial rows. Rows of pits rather widely spaced. Micro-pits of markedly variable size. One specimen with concentric lamellae of uneven height and density, declining anteriorly. Umbo marginal.

Plate 7

Mirilingula ? svalbardensis sp. nov.

Valhallfonna Formation, Profilbekken Member.

1–2. TSGF16978 , paratype, dorsal valve interior and oblique ventrolateral view thereof. Profilbekken Member, 17 m above base. Coll. J. Hansen, 19.07.2008, sample JH-25 .

3. TSGF16971 , paratype, dorsal pseudointerarea. Profilbekken Member, 21 m above base. Coll. J. Hansen, 19.07.2008, sample JH-23 .

Schizotreta sp. 1

Kirtonryggen Formation, Basissletta Member, upper 0.5 m of member. Coll. J. Hansen, 03.08.2008, sample JH-170.

4–6. TSGF17017, dorsal valve exterior, oblique lateral view, and detail of micro-ornamentation thereof.

Schizotreta sp. 2

Kirtonryggen Formation, Nordporten Member, uppermost beds. Coll. J. Hansen, 29.07.2008, sample JH-153.

7–10. TSGF17022, ventral valve exterior, detail of micro-ornamentation on the boundary between larval and postlarval shell, detail of postlarval micro-ornamentation, oblique lateral view of valve.

11. TSGF17021, rugae on postlarval shell.

12–13. TSGF17020, dorsal valve exterior, oblique lateral view thereof.

Schizotreta marginalis sp. nov.

Valhallfonna Formation, Olenidsletta Member, 97 m above base. Coll. J. Hansen, 28.07.2008, sample JH-136.

14–15. TSGF16952 , paratype, dorsal valve exterior, detail of lamellae .

16–17. TSGF16953 , holotype, dorsal valve exterior, oblique lateral view of same .

Remarks. The available material is insufficient for any meaningful comparison to other species. However, Schizotreta sp. 2 from the Nordporten Member appears to differ in having denser, unordered micro-pitting, and Schizotreta marginalis sp. nov. has consistent micro-pits of equal size and stronger concentric ornamentation.

Occurrence. Lower part of Nordporten Member, Kirtonryggen Formation, Basissletta in northeastern Ny Friesland, Spitsbergen.