Morinorhynchus, Havlicek, 1965

Modzalevskaya, Tatiana L., 2003, Silurian and Devonian brachiopods from Severnaya Zemlya (Russian Arctic), Geodiversitas 25 (1), pp. 73-107 : 79-80

Genus Morinorhynchus Havlic˘ek, 1965

Morinorhynchus proprius ( Lopushinskaya, 1965) ( Fig. 7 )

Schuchertella propria Lopushinskaya, 1965: 25 , pl. I, figs 5-8.

Morinorhynchus proprius – Lopushinskaya 1991: 55, pl. I, figs 9-12.

MATERIAL EXAMINED. — Seven specimens from loc. 2, bed 66, loc. 11, beds 6B and 11, Matusevich River, October Revolution Island ( Männik et al. 2002: figs 2, 5); Srednij and Samojlovich formations.

REMARKS

These are small shells (L = 8.3-9.5 mm, W = 7.6?- 11.6 mm, T = 1.4-1.9 mm). The delthyrium is closed by a large pseudodeltidium and a small, almost linear chilidium under which a bilobated cardinal process is situated. The radial ornament is multicostellate. The costellae are rounded, and are increasing by five orders of intercalation. Fine concentric growth-lines cross the costellae. That is why the specimens may be assigned to the genus Morinorhynchus . M. proprius was described by Lopushinskaya from the Omnutakh, Khukta, and Makus formations of East Siberia ( Lopushinskaya 1965: 25). It can probably be mixed with Schuchertella cf. subplana Poulsen, 1943. The juvenile specimen illustrated by Poulsen (1943: 22, pl. 1, figs 22-24) from the Silurian of Greenland as M. cf. plana Conrad, 1842 is similar to M. proprius in having the same shell shape, and a similar pattern of costellae. M. cf. plana of Poulsen (1943) is also similar to M. attenuatus Amsden, 1951 from the Henryhouse Formation of North America ( Amsden 1951: 84, pl. 17, figs 9-14), and from the Khatanzeya and Greben stages in the western Urals and Russian Arctic. However, M. proprius differs from M. cf. plana in having a rounded outline and lower number of costellae.

Superfamily CHONETOIDEA Bronn, 1862 Family CHONETIDAE Bronn, 1862 Genus Sinochonetes Wang, Boucot & Rong, 1981

Figures

FIG. 7. — Morinorhynchus proprius (Lopushinskaya, 1965); A, B, complete shell (N 16/12991), loc. 11, bed 6B, Samojlovich Formation; A, ventral view; B, dorsal view; C, dorsal interior with bilobate cardinal process (N 17/12991), loc. 2, bed 66, Samojlovich Formation. Scale bars: A, B, 5 mm; C, 2 mm.