Linnarssonia bulcurica Pelman

Kouchinsky, Artem, Alexander, Ruaridh, Bengtson, Stefan, Bowyer, Fred, Clausen, Sébastien, Holmer, Lars E., Kolesnikov, Kirill A., Korovnikov, Igor V., Pavlov, Vladimir, Skovsted, Christian B., Ushatinskaya, Galina, Wood, Rachel & Zhuravlev, Andrey Y., 2022, Early-middle Cambrian stratigraphy and faunas from northern Siberia, Acta Palaeontologica Polonica 67 (2), pp. 341-464 : 364-365

Linnarssonia bulcurica Pelman in Pelman and Pereladov, 1986

Fig. 13 .

Material.— Over one hundred calcium phosphatic dorsal and ventral valves, including figured SMNH Br151233– 151239, from samples 1/16.5, K1/8B, 8/32, Kuonamka Formation, Bol’shaya Kuonamka and Malaya Kuonamka rivers, Siberia, Russia. Kounamkites and Tomagnostus fissus – Acadoparadoxides sacheri zones, Amgan and lower Mayan stages (correlated with the Wuliuan–lower Drumian stages).

Description.— Shell rounded in outline, covered with fine concentric growth lines with sets of drapes. Ventral valve conical. Umbo situated anteriorly to the posterior margin of ventral valve. Ventral pseudointerarea steeply procline. Apical foramen in a short tube. External pedicle opening not enclosed within brephic shell. Dorsal valve gently convex, rounded with a marginal umbo. Dorsal pseudointerarea orthocline, with a broad median groove and short propareas. Dorsal interior with low median ridge. Brephic shell broadly oval in outline, 200–220 μm long and 220–270 μm wide, covered with pits, ca. 1 μm in diameter, becoming less distinct towards the margin of the brephic shell.

Remarks.— See comparative discussion in Ushatinskaya and Korovnikov (2019).

Stratigraphic and geographic range.— Amgan and lower Mayan stages (correlated with the Wuliuan and lower Drumian stages), Siberian Platform.

Figures

Fig. 13. Lingulid brachiopod Linnarssonia bulcurica Pelman in Pelman and Pereladov, 1986 from the middle Cambrian Kuonamka Formation, Malaya Kuonamka and Bol’shaya Kuonamka rivers, Siberia, Russia; sample 1/16.5 (A–D, F, G) and sample 8/32 (E). A–C. Ventral valves, SMNH Br151233– 151235, respectively. A1, external surface; A2, lateral view; A3, close-up showing brephic shell. D, F, G. Dorsal valves, SMNH Br151237–151239, respectively. D2, close-up of the brephic shell; D3, enlargement with pits on the surface. E. Specimen with both valves preserved, SMNH Br151236. E1, external surface; E2, oblique lateral view. Scale bar: 1 mm (A1, A2, B, C, D1, E, F), 500 µm (G), 250 µm (A3, D2), and 12.5 µm (D3).