Ripidiorhynchus huotinus ( Verneuil, 1845 )

Sokiran, Elena V., 2002, Frasnian-Famennian extinction and recovery of rhynchonellid brachiopods from the East European Platform, Acta Palaeontologica Polonica 47 (2), pp. 339-354 : 346-348

Ripidiorhynchus huotinus ( Verneuil, 1845)

Figs. 10A–I , 11 , 12 .

Terebratula huotina ; Verneuil 1845: 81, pl. 10: 4.

Rhynchonella livonica ; Venyukov 1886: 534, pl. 5: 2, 3, 7. Camarotoechia huotina ; Nalivkin 1934: 22, pl. 2: 4–6.

Camarotoechia zadonica n. sp.; Nalivkin 1934: 23, pl. 3: 1–8.

Camarotoechiazadonica;SarychevaandSokolskaya1952:163,pl.46: 246.

Camarotoechia huotina ; Ljashenko 1959: 205, pl. 76: 1, 2.

Camarotoechia zadonica ; Ljashenko 1959: 205, pl. 76: 3–5.

Emended diagnosis.—Internally R. huotinus have short septum and lenticular crura, which are strongly curved ventrally. Closely related R. griasicus differs mainly by smaller sizes, shallow and wide sulcus, combined with the greatest width of shell situated nears the anterior margin.

Material.— More than 50 specimens.

Remarks.— Sartenaer (1966) included in the genus Ripidiorhynchus five early Famennian species from central regions: Terebratula huotina Verneuil, 1845 , Camarotoechia cernosemica Nalivkin, 1934 , C. zadonica Nalivkin, 1934 , C. brodica Nalivkin, 1934 , and C. griasica Nalivkin, 1934 . Originally, Terebratula huotina was described by Verneuil (1845) from Zadonsk region of the central Russia, i.e. from the Zadonsk Horizon. Verneuil (1845) noted that this species occurs in the Orel district and in the Chudovo district to the northwest. Thus, he apparently combined the early Famennian ( Pa. crepida Zone ) R. huotinus with the early Frasnian R. livonicus . Nalivkin (1934) described Camarotoechia zadonica from the Zadonsk Horizon of the Elets and Russkii Brod districts. According to Nalivkin (1934), the main difference between this species and C. huotina , concerns a narrower fold, higher triangular tongue and more numerous ribs in C.zadonica . He also noted that C.zadonica has 12–15 ribs on each side of the shell, 2–4 in sulcus, and 2–3 parietal ribs. On the other hand C.huotina shows 15–18 ribs on each flank of the valve, 2–4 in sulcus, and 2–3 parietal ribs. Nalivkin (1934: 22–23) wrote that C. huotina is a variety of C. zadonica , because they are similar and occur together, but the latter species has a wider distribution. The development of dorsal fold curvature near the anterior margin, as the diagnostic feature of huotina , depends on the age of the shell ( Fig. 11 ). Thus, Ripidiorhynchuszadonicus should be regarded as a junior synonym of Ripidiorhynchus huotinus .

Nalivkin (1934) described C. cernosemica ( Fig. 10Q–T ) from the Zadonsk Horizon. This species co−occurs with C. zadonica and C. huotina , and, according to Nalivkin, is distinguished by its flat umbonal region of the dorsal valve, wide beak and transversally elliptical shell outline.

Occurrence.—Early Famennian, Pa.crepida Zone, Zadonsk Horizon , central Russia.

Figures

Fig. 10. A–I. Ripidiorhynchushuotinus (Verneuil, 1845). A–D. CNIGR 763/4572 from the early Famennian, Zadonsk Horizon, central regions of Russia, in ventral, dorsal, anterior, and lateral views. Sosna River basin. E–I.CNIGR 4/13076, ventral, dorsal, lateral, posterior, and anterior views. Kamenka village. J–Q. Ripidiorhynchusgriasicus (Nalivkin, 1934), from early Famennian, Elets Horizon, Sosna River basin. J–M. Neotype. CNIGR 266/4572, ventral, dorsal, anterior, and lateral views. N–Q. CNIGR1046/4572, ventral, lateral, dorsal, and anterior views. R–U. Ripidiorhynchuscernosemicus (Nalivkin, 1934) CNIGR 862/4572, ventral, dorsal, anterior, and lateral views. Early Famennian, Zadonsk Horizon, Sosna River basin. All × 1.5.

Fig. 11. Growth changes of shell of the Ripidiorhynchushuotinus (Verneuil, 1845) from the early Famennian, Zadonsk Horizon, Kamenka village, showing different fold deflection of the dorsal valve. A. CNIGR 5/13076. B. CNIGR 6/13076. C. CNIGR 4/13076.

Fig. 12. A. Transverse serial section of Ripidiorhynchus huotinus (Verneuil, 1845). Numbers refer to distances in mm from the top of the ventral umbo, CNIGR 7/13076. B. Longitudinal section. CNIGR 8/13076. C. Reconstruction of the crural plates, CNIGR 9/13076. Early Frasnian, Zadonsk Horizon, Kamenka village, Elets region. D. CNIGR 10/13076 Zadonsk Horizon, Zadonsk region.