Proboscisambon, Havlicek and Mergl, 1982

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 : 400

Proboscisambon ? sp.

Fig. 4D, E .

Material.— Seven specimens embedded in rock. Porkuni Regional Stage , Kuldiga Formation , Hirnantian ( Upper Ordovician ); southwestern Estonia and western Latvia. Drill core and depth (in meters) of sample intervals with brachiopods. Depth interval of fragmentary specimens is marked by “?”. Collection GIT 542 : Aizpute-41, 997.7–1000.35; Stirnas-18, 908.2; Riekstini-15, 858.6; Ruhnu-500, 613.5; Vilcini-15, 909.5;? Prabut Formation ( Podhalańska 2009): Petrobaltic S-8, 2618.2–2618.28 (sample 47 from the interval 2614.4– 2633 m) .

Remarks.—Small, laterally elongated shells, up to 6.5 mm wide and 4.2 mm long with weakly developed ornament of concentric filae and few costae (nine on the largest valve) appearing at about 2.5 mm from the umbo reminiscent of the genus Proboscisambon first described from Bohemia ( Havlíček and Mergl 1982). The Baltic specimens have obtuse cardinal angles and almost flat valves. The studied specimens are similar to those Paramalomena in having a fine radial ornament differing in lacking the growth lines characteristic of that genus. Depending on preservation, the small Glyptomeninae may be erroneously assigned to the genus Foliomena ; see for example, one specimen (GIT 542-53) from the lowermost Porkuni Regional Stage in the Stirnas-18 core ( Hints et al. 2010). This specimen, in fact, belongs to the genus Proboscisambon .

Figures

Fig. 4. Strophomenoid brachiopods from the Kuldiga Formation of the Porkuni Regional Stage, Hirnantian (Upper Ordovician), East Baltic, western Latvia (A–F, H) and southwestern Estonia (G). A, B, F–H. Paromalomena polonica (Temple, 1965). A. Dorsal valve, GIT 542-299, Mežmali-16, depth 911.8 m, exterior view. B. Dorsal valve, GIT 542-352-1, Adze-6, 844.5 m, split into two parts: exterior view (B1) and impression (B2). F. Dorsal valve, GIT 542-377, Aispute-41, 884.4 m, exterior view.G. Dorsal valve, GIT 542-361, Ikla, 535.3 m, exterior view. H. Dorsal valve, GIT 542-355, Mežmali-16, 912.2 m, exterior view (H 1) and view of the chilidium (H2). C. Eostropheodonta cf. parvicostellata Rong, 1984. Dorsal valve, GIT 542-365, Aispute-41, depth 988.7 m, exterior view. D–E. Proboscisambon? sp. D. Mould of dorsal valve, GIT 542-53, Stirnas-18, depth 908.2 m, exterior view. E. Dorsal valve, GIT 542-322-1, exterior view; Riekstini-15, 858.6 m. Scale bars 2 mm.