Coolinia 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 : 405

Coolinia sp.

Fig. 6C, D, F, G .

Material.— Seven specimens embedded in rock. Porkuni Regional Stage , Kuldiga Formation , Hirnantian ( Upper Ordovician ); western Latvia, southwestern Estonia. Drill core and depth (in meters) with brachiopod samples. Collection GIT 542 : Mežmaļi-16, 912.6; Krjukai, 968.6; Ruhnu-500, 612.9, Stirnas-18, 899.0, 908.3 m; Vilcini-15, 906.4; collection LDM G: Dizrungi-17, 894.5 .

Remarks.—Only few specimens of the genus Coolinia are known from the East Baltic sections. Coolinia dalmani Bergström, 1968 from the Dalmanitina Beds in Västergötland, Sweden, and some comparative species from the topmost Ordovician and lowermost Silurian in USA ( Amsden 1974) have posterior costae and costellae curving towards the posterior margin of the valve. This type of ribbing is developed most clearly on specimens of another chilidopsid genus, Valdaria ( Bassett and Cocks 1974) first described from the Silurian rocks of Gotland. However, the position of the posterior costae, which may have some taxonomic value, is not clear on the Baltic specimens; they are subparallel rather than curving toward the margin.

Description.— The Baltic specimens have transversely suboval, weakly biconvex shells, up to about 12 mm wide and 7 mm long; the maximum width corresponds to width of the hinge line or is a little shorter. Radial ornament of up to 40 costae and costellae, among them 18 primary costae.

One dorsal fragment ( Fig. 6F ) displays prominent cardinal lobes partly covered by a short chilidium, and socket ridges divergent postero-laterally like those of the genus Coolinia . Interior of one incomplete ventral valve ( Fig. 6G ) has a small delthyrial chamber and dental plates diverging at about 70 degrees; the muscle field is not differentiated on the valve floor which is covered by impressions of the external ornament.

Figures

Fig. 6. Leptostrophiid brachiopods from the Kuldiga Formation of the Porkuni Regional Stage, Hirnantian (Upper Ordovician), East Baltic, western Latvia A–E, G) and southwestern Estonia (F). A. Eostropheodonta hirnantensis (M`Coy, 1851), Taagepera, depth 413.9 m, moulds of ventral valves, GIT 542-337/1 A1) and GIT 542-337/2 (A2), exterior views. B, E. Eostropheodonta cf. parvicostellata Rong, 1984. B. Shell, GIT 542-381, Vilcini-19, 906.4 m, exterior view of dorsal valve (B1) and view on interarea (B2). E. Mould of dorsal valve, LDM G328-12, Priekule-33, 1395.6 m, exterior view. C, D, F, G. Coolinia sp. C. Mould of ventral valve, LDM G328-26, Dižrungi-17, 984.5 m, exterior view. D. Ventral valve, LDM G328-26, Dizrungi-17, 984.5 m, exterior view. F. Fragment of dorsal valve, GIT 542-364, Ruhnu-500, depth 612.9 m, view of cardinalia (F1) and exterior view (F2). G. Incomplete ventral valve, GIT 542 48-2, Stirnas-18, 899.0 m, interior view. Scale bars 2 mm.