Leptostrophiidae Caster, 1939

Musteikis, Petras & Cocks, L. Robin M., 2004, Strophomenide and orthotetide Silurian brachiopods from the Baltic region, with particular reference to Lithuanian boreholes, Acta Palaeontologica Polonica 49 (3), pp. 455-482 : 464

Family Leptostrophiidae Caster, 1939 Genus Brachyprion Shaler, 1865

The type species of Brachyprion is B. leda from the mid−Aeronian to Telychian Jupiter Formation of Anticosti Island, Canada, revised by Rong and Cocks (1994: 682). This is much less convex than the Brachyprion arenacea ( Davidson, 1871) , which was placed within Brachyprion by Cocks (1967) and which was recorded from the Aeronian Rytteråker Formation of the Oslo region by Cocks and Baarli (1982: 88). Similarly convex shells were recorded as Brachyprion sp. from the Wenlock and Ludlow of Gotland by Bassett and Cocks (1974: 15). Following the revision of B. leda by Dewing (1999), the generic identity of all these forms requires revision. Modzalevskaya (1985: 60, pl. 1: 1, 2) recorded Brachyprion cf. robustum Twenhofel from the Llandovery of Novaya Zemlya. B. robustum itself, which was originally described from Anticosti Island, Canada, has now been placed within the synonymy of B. leda by Dewing (1999), but we have seen no material from Baltica that could be included within that species. Rybnikova (1966: 85; 1967: 194) described and illustrated what she determined as Brachyprion costatula (Barrande) from the Lower Ludlow of Latvia, Lithuania, Podolia, the Urals and central Asia. Her illustrated shells may be reassigned to Shaleria ( Rubel et al. 1984, and see below).

Rybnikova (1966: 80; 1967: 194) also described a new species, Brachyprion kurzemensis from the Ludlow of Latvia, but without illustrating the ventral interior. The cardinalia of the dorsal valve are not identical to the type species of Brachyprion , and the species remains unassigned to a definite genus until better material becomes available. We have also found similar material from the Upper Ludlow of the Milaičiai−103 borehole (1206.5– 1202.75 m) ( Fig. 5F), which we have identified here as Brachyprion? kurzemensis , but there are no interiors available from Lithuania. It occurs in the Paprieniai and Birštonas formations (Sheinwoodian and Homerian) in east Lithuania; Rusnė (Gorstian), Pagėgiai (Ludfordian), Minija and Jūra (Pridoli) formations in west Lithuania (Appendix).