Cyrtospirifer rudkinensis Ljaschenko, 1959

Sokiran, Elena V., 2006, Early-Middle Frasnian cyrtospiriferid brachiopods from the East European Platform, Acta Palaeontologica Polonica 51 (4), pp. 759-772 : 765

Cyrtospirifer rudkinensis Ljaschenko, 1959

Figs. 5C, D , 7 .

1959 Cyrtospirifer rudkinensis sp. nov.; Ljashenko 1959: 161, pl. 39: 1–4, pl. 40: 2, 3.

Material.—Fifty well preserved and eight flattened shells collected by the author from Rudkino village, Don river, Central Devonian Field, and 61 complete shells from Tsylma, Pizhma Pechorskaya and Myla rivers, Middle Timan from Feodosij N. Chernyshev’s collection.

Remarks.—This species differs from Cyrtospirifer schelonicus Nalivkin, 1941 in having a more inflated ventral valve with a lower interarea, narrower delthyrium, wider umbo with a strongly curved beak, and coarser ribs. C. rudkinensis differs from similar C. placitus Stainbrook, 1945 in having generally more swollen umbo and more straight lateral margins.

Occurrence.—Middle Frasnian, Palmatolepis punctata – Pa. jamieae zones, Semiluki Horizon, Central Devonian Field; Kraipol Formation, Middle Timan.

Figures

Fig. 5. Cyrtospiriferids from Middle Frasnian of the Main and Central Devonian Fields. A, B. Cyrtospirifer schelonicus (Nalivkin, 1941), Svinord Beds, Main Devonian Field. A. CNIGR 2/13157, ventral (A1), dorsal (A2), posterior (A3), anterior (A4), and lateral (A5) views. B. CNIGR 3/13157, ventral (B1), dorsal (B2), posterior (B3), anterior (B4), and lateral (B5) views. C, D. Cyrtospirifer rudkinensis Ljaschenko, 1959, Semiluki Horizon, Central Devonian Field. C. CNIGR 4/13157 ventral (C1), dorsal (C2), posterior (C3), anterior (C4), and lateral (C5) views. D. CNIGR 5/13157 ventral (D1), dorsal (D2), posterior (D3), anterior (D4), and lateral (D5) views.

Fig. 7. Transverse serial sections of complete shell of Cyrtospirifer rudkinensis (Ljaschenko, 1959), Middle Frasnian, Semiluki Horizon, Central Devonian Field. CNIGR 7/13157. Distance in mm is measured from the posterior tip of ventral beak.