Lanceomyonia Havlíček, 1960

Baliński, Andrzej, 2012, The brachiopod succession through the Silurian-Devonian boundary beds at Dnistrove, Podolia, Ukraine, Acta Palaeontologica Polonica 57 (4), pp. 897-924 : 912-914

Genus Lanceomyonia Havlíček, 1960

Type species: Terebratula tarda Barrande, 1847 ; Pridoli, Silurian; Dvorce , central Bohemia .

Lanceomyonia borealiformis ( Siemiradzki, 1906) Fig. 12F–H .

1906 Rhynchonella borealiformis Szajnocha ; Siemiradzki 1906: 171, pl. 7: 3–5.

1978 Lanceomyonia borealiformis ( Siemiradzki, 1906) ; Rubel and Teller 1978: 477–478, pl. 3: 8–9.

1985 Lanceomyonia borealiformis ( Siemiradzki, 1906) ; Nikiforova et al. 1985: 38 [full synonymy herein].

Material.—9 complete shells and 7 fragments of shells and single valves. In the studied section the stratigraphically oldest specimens come from 1.0 m and 1.5 m above the S–D boundary (bed 2 and 5, respectively). Other specimens were recovered 5.5 m (beds 47–48) above the boundary and from a loose block representing the uppermost part of the section.

Description.—Shell up to 16.4 mm in length, dorsibiconvex, transversely subelliptical to subcircular in outline, slightly wider than long, uniplicate. Ventral valve regularly convex in lateral profile with strongly incurved beak in large shells; sulcus appears at about 7–8 mm from the umbo, rather shallow but clearly separated from flanks by slightly stronger ribs; tongue long, with convex bottom. Dorsal valve strongly convex; fold appears 5–6 mm from umbo, rather low, but clearly delimited laterally by slightly stronger bordering ribs. Posterior 5–9 mm of the shell surface smooth, anteriorly radially ribbed; ribs simple, rounded, very variable in number; 4–5 ribs on fold, 3–4 in sulcus, and 7–11 ribs on each flank.

Remarks.—This species was reported by Kozłowski (1929), as Camarotoechia (Wilsonia) tarda ( Barrande, 1847) , from the Borshchiv and Chortkiv horizons. Nikiforova et al. (1985) identified the species with certainty, however, only

http://dx.doi.org/10.4202/app.2011.0138

from the Khudykivtsi and Mytkiv beds of the Borshchiv Horizon. The specimens studied here from the Dnistrove section agree closely with those illustrated by Kozłowski (1929: pl. 7: 26) from the Borshchiv Horizon. He described the species in great detail, both externally and internally, and gave the statistic range of its morphologic variability.

Stratigraphic and geographic range.— Nikiforova (1954) reported the species from several localities in Podolia from the Borshchiv Horizon. Although Kozłowski (1929) and Nikiforova (1954) reported the species from many localities in Podolia they did not list Dnistrove among them. Later, however, Nikiforova et al. (1972) mentioned L. borealiformis from Volkovtsy (= Dnistrove).

Figures

Fig. 12. Rhynchonellide brachiopods from the Silurian–Devonian boundary beds at Dnistrove (Podolia, Ukraine). A–D. Sphaerirhynchia gibbosa (Nikiforova, 1954). A–C. Three complete shells ZPAL Bp. 56/59 (A), ZPAL Bp. 56/60 (B), and ZPAL Bp. 56/61 (C) in dorsal (A1, B1, C1), ventral (A2, B2, C2), lateral (A3, B3, C3), posterior (A4, B4, C4), and anterior (A5, B5, C5) views. D, E. Juvenile, ZPAL Bp. 56/62 (D) and gerontic, ZPAL Bp. 56/63 (E) shells in dorsal (D1, E1), lateral (D2, E2), and posterior (D3, E3) views. F–H. Lanceomyonia borealiformis (Siemiradzki, 1906), three well preserved shells ZPAL Bp. 56/65 (F), ZPAL Bp. 56/66 (G), and ZPAL Bp. 56/67 (H), in different individual age in dorsal (F1, G1, H1), ventral (F2, G2, H2), lateral (F3, G3, H3), posterior (F4, G4, H4), and anterior (F5, G5, H5) views; all from beds 47–48.