Cyrtospirifer Nalivkin

Sokiran, Elena V., 2006, Early-Middle Frasnian cyrtospiriferid brachiopods from the East European Platform, Acta Palaeontologica Polonica 51 (4), pp. 759-772 : 764-765

Genus Cyrtospirifer Nalivkin in Frederiks, 1924 Cyrtospirifer schelonicus Nalivkin, 1941

Figs. 5A, B , 6 , 10G, H .

1886 Spirifer Verneuili Murchison, 1840 ; Venyukov 1886: 64–79, pl. 4: 4.

1886 Spirifer Archiaci Murchison, 1840 ; Venyukov 1886:64–79, pl. 4: 1.

1916 Spirifer verneuili Murchison, 1840 ; Obrouchev 1916, pl. 2: 22, 23.

1941 Cyrtospirifer schelonicus sp. nov.; Nalivkin 1941: 178, pl. 6: 1–5.

1947 Cyrtospirifer schelonicus Nalivkin, 1941 ; Nalivkin 1947: 113, pl. 27: 1, 2.

Material.—Twenty four well preserved complete shells and eight disarticulated valves collected by Roman F. Hecker near Koloschka river, NW of EEP and in addition three complete shells recently collected.

Remarks.—According to the original description by Nalivkin (1941) Cyrtospirifer schelonicus is a morphologically variable species that includes the shells formerly described from the Svinord Beds of the Main Devonian Field by Venyukov (1886) under the names Spirifer archiaci , Spirifer verneuili , and Spirifer tenticulum . Nalivkin (1941) recognized several morphotypes within the species: (1) transverse, subtrapezoidal shells with a high triangular ventral interarea superficially similar to Cyrtospirifer verneuili ( Murchison, 1840) ; (2) shells similar to C. disjunctus ( Sowerby, 1840) , and (3) transverse shells with a subpyramidal ventral valve, a broad ventral interarea and a low dorsal median fold seemingly comparable to C. tenticulum ( Verneuil, 1845) . The species, however, can be easily distinguished from C. verneuili ( Murchison, 1840) in having less numerous costae, more concave and wider ventral interarea and a lower dorsal median fold.

Brice (1970) described Cyrtospirifer schelonicus from the Middle Frasnian of Afghanistan (Ghouk region). Four shells illustrated by her ( Brice 1971: 128–132, pl. 7: 1–4) show great variability in general shell outline and convexity, shape of the cardinal extremities, and development of the ventral interarea. However, one of those shells (i.e., Brice 1970: pl. 7: 3) seems to be close to C. schelonicus from the Main Devonian field.

Occurrence. —Middle Frasnian, Palmatolepis punctata – Pa. hassi zones, Svinord and Il'men Beds, Main Devonian Field.

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. 6. Transverse serial sections of complete shell of Cyrtospirifer schelonicus (Nalivkin, 1941), Middle Frasnian, Svinord Beds, Main Devonian Field. CNIGR 6/13157. Distance in mm is measured from the posterior tip of ventral beak.

Fig. 10. Cyrtospiriferids from Middle Frasnian of the Main and Central Devonian Fields. A–C. Cyrtospirifer tenticulum (Verneuil, 1845). A. Buregi Beds, Main Devonian Field. CNIGR 93/6993, neotype, ventral (A1), dorsal (A2), posterior (A3), and lateral (A4) views. B, C Semiluki Horizon, Central Devonian Field. B. CNIGR 3535/2858, ventral (B1), dorsal (B2), posterior (B3), anterior (B4), and lateral (B5) views, and shell surface showing microornament (B6). C. CNIGR 3534/2858, ventral (C1), dorsal (C2), posterior (C3), anterior (C4), and lateral (C5) views. D, E. Cyrtospirifer lictor Nalivkin, 1930, Semiluki Horizon, Don river, Central Devonian Field. D. CNIGR 3530/2858, ventral (D1), dorsal (D2), posterior (D3), anterior (D4), and lateral (D5) views. E. CNIGR 3531/2858, ventral (E1), posterior (E2), anterior (E3), and lateral (E4) views. F. Cyrtospirifer sp. A, Porkhov Beds, Main Devonian Field. CNIGR 11/13157, ventral (F1), posterior (F2), anterior (F3), and lateral (F4) views. G, H. Cyrtospirifer schelonicus (Nalivkin, 1941), Svinord Beds, Main Devonian Field. G. CNIGR 88/6993, ventral (G1), dorsal (G2), posterior (G3), and lateral (G4) views. H. CNIGR 87/6993, ventral (H1), dorsal (H2), posterior (H3), and lateral (H4) views. I. Cyrtospirifer tschudovi Nalivkin, 1941, Chudovo Beds, Main Devonian Field, CNIGR 1/6993, ventral (I1) and posterior (I2) views.