Ripidiorhynchus griasicus ( Nalivkin, 1934 )

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 : 348-349

Ripidiorhynchus griasicus ( Nalivkin, 1934)

Figs. 10J–Q , 13 .

Rhynchonella livonica ; Venjukov 1886: pl. 5: 6.

Camarotoechia griasica ; Nalivkin 1934: 23, pl. 3: 1–6. Camarotoechia brodica ; Nalivkin 1934: 24, pl. 3: 9–14. Camarotoechia griasica ; Nalivkin 1947: 37, pl. 19: 8.

Camarotoechia brodica ; Ljashenko 1959: 212, pl. 81: 4, 5. Camarotoechia griasica ; Ljashenko 1959: 212, pl. 81: 6, 7.

Neotype.—Complete shell from the Nalivkin collection (1934), CNIGR 266 /4572, Fig. 10I–L .

Emended diagnosis.—Small Ripidiorhynchinae externally closely related to Hunanotoechia tieni described by Ma (1993) from the late Frasnian of the central Hunan, but latter have a broader septalium without connectivum.

Material.— Above 40 specimens.

Remarks.— Camarotoechia griasica was described by Nalivkin (1934) from the Elets Horizon of the central regions of the Russia (Griasi, Lipetsk, Elets, and Russkii Brod districts). Nalivkin (1934) also described C.brodica , as that rare form co−occurs with the former species in the Elets Horizon of Russkii Brod district. According to Nalivkin (1934: 24) the diagnostic characters of C.brodica are its flattened lateral flanks and a more convex dorsal valve. He noted that C. griasica has 8–12 lateral ribs, 4–5 ribs in sulcus, and 1–2 parietal ribs, whilst C. brodica bears 8–12 lateral ribs, 4 ribs in the sulcus and 1–2 parietal ribs. However, the greater convexity of the dorsal valve of C. brodica (see Nalivkin 1934: pl. 4: 11I–L) is a variable feature. External and internal shell morphology of these co−occuring species is very similar; consequently, C. brodica is considered here as a junior synonym of C. griasica .

Nalivkin originally has not chosen holotypes for C. griasica and C. brodica , therefore, a neotype of Ripidiorhynchus griasicus is selected here.

Occurrence.—Early Famennian, Pa. crepida – Pa. rhomboidea zones, Elets 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. 13. Transverse serial sections of Ripidiorhynchus griasicus (Nalivkin, 1934) from the early Famennian, Elets Horizon. Numbers refer to distances in mm from the top of the ventral umbo. A. CNIGR 11/13076. Argamach quarry, Elets region, B. CNIGR 12/13076. Lavy quarry, Elets region.