Onniella sp.

Hints, Linda & Harper, David A. T., 2015, The Hirnantian (Late Ordovician) brachiopod fauna of the East Baltic: Taxonomy of the key species, Acta Palaeontologica Polonica 60 (2), pp. 395-420 : 410

Onniella sp.

Fig. 11A–B, D, H–I .

Material.— Eight specimens. Porkuni Regional Stage , Kuldiga Formation , Hirnantian ( Upper Ordovician ); western Latvia. Drill core and depth (in meters) of sample intervals with brachiopods. Collection GIT 542 : Adze-6, 822.5; Aispute-41, 1001.15; Kandava-26, 964.5; Krjukai , 968.6; Mežmaļi, 916.3; Riekstini-15, 860.85–861.8; Vilcini-19, 914.5. Collection LDM G: Dižrungi-17, 896.0 .

Remarks.—Shell small, biconvex, ventral valve slightly carinate, dorsal valve sulcate. The shell outline and fascicostellate ornament is similar to that of Onniella trigona from the East Baltic ( Rubel 1962, 2011; Hints 1975) and Onniella tricapitata Jin and Zhan, 2008 from the Ellis Bay Formation on Anticosti Island ( Jin and Zhan 2008). However, the Latvian specimens differ from both species in lacking reticulat- ed growth lines ( Jin 2012). Comparisons are difficult with Onniella kalvoy a Cocks, 1982 from the central Oslo Region, Norway ( Cocks 1982) due to insufficient data on the East Baltic specimens. Two smaller specimens ( Fig. 11D, I ) with stronger costae and costellae, however, could belong to another species or merely represent early growth stages.

Figures

Fig. 11. Dalmanellid brachiopods from the Kuldiga Formation of the Porkuni Regional Stage, Hirnantian (Upper Ordovician), East Baltic, western Latvia A–D, F–I) and southwestern Estonia (E). A, B, D, H, I. Onniella sp. A. Dorsal valve, GIT 542-66, Aispute-41, depth 1001.15 m, exterior view. B. Ventral valve, LDM 382-50, Dižrungi-17, 896.0 m, ventral view. D. Shell, GIT 542-471, Riekstini-15, 860.85, dorsal (D 1), ventral (D 2), and lateral (D 3) views. H. Dorsal valve, GIT 542-480, Krjukai, 968.6 m, dorsal exterior view. I. Shell, GIT 542-472, Kandava-26, 964.5 m, ventral (I 1) and dorsal (I 2) views. C, E, F. Draborthis cf. caelebs Marek and Havliček, 1967. C. Dorsal valve, GIT 542-392, Riekstini-15, 857.5, interior view. E. Dorsal valve, GIT 542- 67, Ruhnu-500, 914.0 m, exterior view. F. Dorsal valve, GIT 542-4393, Mežmali-16, 913.2 m, interior view.G. Drabovia sp., dorsal valve, GIT 542-473, Mežmali-16, 910.1 m, interior view. Scale bars 2 mm.