Cyrtospirifer tenticulum ( Verneuil, 1845 )

Sokiran, Elena V., 2006, Early-Middle Frasnian cyrtospiriferid brachiopods from the East European Platform, Acta Palaeontologica Polonica 51 (4), pp. 759-772 : 766-769

Cyrtospirifer tenticulum ( Verneuil, 1845)

Figs. 10 A, B , 11 , 12 .

1845 Spirifer tenticulum sp. nov.; Verneuil in Verneuil, Murchison, and Keyserling 1845: 159, pl. 5: 7.

1930 Spirifer (Cyrtospirifer) tenticulum ( Verneuil 1845) ; Nalivkin 1930: 76, pl. 7: 4, 8, 9.

1941 Cyrtospirifer tenticulum ( Verneuil 1845) ; Nalivkin 1941: 180, pl. 7: 3–5.

1947 Cyrtospirifer tenticulum ( Verneuil 1845) ; Nalivkin 1947: 115, pl. 27: 5, 6.

2000 Tenticospirifer tenticulum ( Verneuil 1845) ; Ma and Day 2000: 451, fig. 3, 4.1–4.3, 4.5, 5.1–5.3.

Neotype: Complete shell CNIGR 93 /6993 designed herein, illustrated in Nalivkin (1941: pl. 7: 5) and re−illustrated here in Fig. 10A .

Material.—Twelve complete shells and one ventral valve from Roman F. Hecker’s collection (Il'men lake region) and twenty nine ventral and seven dorsal valves recently collected from the Psizha river banks and old quarry near Buregi village (Il'men lake region, Main Devonian Field).

Remarks.— Nalivkin (1977) noted that type specimens of several species described by Verneuil (1845) and deposited in the l’Ecole Nationale Superieure des Mines de Paris are partly lost as is the case with types of Spirifer tenticulum . Therefore, the neotype of Cyrtospirifer tenticulum is selected here to resolve some uncertainties in affinities and taxonomy of the species ( Fig. 10A ).

Tien (1938) selected Spirifer tenticulum Verneuil, 1845 , as the type species of Tenticospirifer . Subsequently most of researchers ( Paeckelmann 1942; Rzhonsnitskaya 1952; Vandercammen 1959; Sidjachenko 1962; Talent and Gratsianova 1986; Alekseeva et al. 1996) considered this taxon as junior synonym of Cyrtospirifer . Beznosova (1959), Ljaschenko (1959), Bublichenko (1971, 1974), Ma and Day (2000), and Johnson (2006) regarded Tenticospirifer as valid taxon. In the last comprehensive revision of the Family Cyrtospiriferidae published by Ma and Day (2000) Tenticospirifer was defined as having a subpyramidal ventral valve with catacline to slightly procline interarea, narrow delthyrium, short delthyrial plate, in−filled notothyrial cavity of the dorsal valve by secondary shell material, lacking a myophragm bisecting dorsal muscle field, smaller numbers of ribs in the ventral sulcus and on the dorsal fold. In addition Cyrtospirifer lictor Nalivkin, 1930 from the Middle Frasnian of central Russia and some other species from North America and Europe were assigned by these authors to Tenticospirifer .

However, observations on individual and ontogenetic changes in several species of Cyrtospirifer from the Main Devonian Field and Central Devonian Field suggest that most of listed diagnostic features are in a fact present in various species of Cyrtospirifer and sometime their expression is a matter of intraspecific variation. In particular, the juvenile shells of Cyrtospirifer tenticulum have 4 ribs in sulcus whereas in the adult specimens this number increases up to 9. By comparison, Cyrtospirifer schelonicus has 7 to 14 ribs in the sulcus. Cyrtospirifer lictor that was assigned to Tenticospirifer by Ma and Day (2000) has up to 14 ribs in the sulcus. The specimen of Tenticospirifer tenticulum (unfortunately without precise geographical location) illustrated in the recently revised Treatise ( Johnson 2006: 1729, fig 1133: 3) has 16–17 sinal ribs, while here selected neotype has eight ribs. A notothyrial cavity filled with secondary shell can be observed in gerontic shells of Cyrtospirifer schelonicus ( Fig. 6 ). Inclination of the ventral interarea in Cyrtospirifer tenticulum varies from catacline to apsacline (see Nalivkin 1930: pl. 7: 4, 8, 9; Nalivkin 1941: pl. 7: 3–5) whereas in Cyrtospirifer lictor it can be slightly apsacline (see Nalivkin 1930: pl. 7: 5). By contrast, some populations of Cyrtospirifer schelonicus include specimens with a catacline ventral interarea ( Fig. 10H ) and a subpyramidal ventral valve. Thus, we prefer to follow the opinion of those authors who regard Tenticospirifer as a synonym of Cyrtospirifer .

Cyrtospirifer tenticulum differs from the type species of Cyrtospirifer , i.e., C. verneuili , in having pyramidal ventral valve and less numerous sinal and lateral plications.

Occurrence.—Middle Frasnian, Palmatolepis punctata – Pa. hassi zones, Buregi Beds, Main Devonian Field, Semiluki Horizon, Central Devonian Field, Kraipol Formation, Middle Timan.

Figures

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.

Fig. 11. Transverse serial sections of complete shell of Cyrtospirifer tenticulum (Verneuil, 1845), Middle Frasnian, Buregi Beds, Main Devonian Field. CNIGR 12/13157. Distance in mm is measured from the posterior tip of ventral beak.

Fig. 12. Transverse serial sections of complete shells of Cyrtospirifer tenticulum (Verneuil, 1845), Middle Frasnian, Buregi Beds, Main Devonian Field. A. CNIGR 13/13157. B. CNIGR 14/13157. C. CNIGR 15/13157. Distance in mm is measured from the posterior tip of ventral beak.

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.