Dictyonina pannula ( White, 1874 )

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 : 369-370

Dictyonina pannula ( White, 1874)

Fig. 18 .

Material.—Single dorsal and four ventral calcium phosphatic valves, including figured SMNH Br151265–151268, from sample 19/92, Yunkyulyabit-Yuryakh Formation, Khorbusuonka River, Siberia, Russia. Anopolenus henrici – Corynexochus perforatus Zone, Mayan stage (correlated with the Drumian Stage).

Description.—Ventral valve semicircular in outline, up to 1.4 mm wide and 1.2 mm long, strongly convex with prominent apex overhanging the posterior margin. Ventral interarea with a broad subtriangular delthyrium. Dorsal valve slightly convex, notothyrium broadly triangular. The outer surface of both valves ornamented with concentric wavy folds superimposed with radially oriented plication. Brephic shell, 400– 550 μm wide and 250–350 μm long, with a smooth surface. Brephic ventral valve with a single bulge at the apex. Brephic dorsal valve semicircular and without distinct elevations.

Remarks.—See description and comparison by Rowell 1980), Basset-Butt (2016), Pegel et al. (2016).

Stratigraphic and geographic range.—Wuliuan–Guzhangian stages, Siberian Platform and Laurentia.

Figures

Fig. 18. Paterinid brachiopod Dictyonina pannula (White, 1874) from the middle Cambrian Yunkyulyabit-Yuryakh Formation, Khorbusuonka River, Siberia, Russia; sample 19/92. A, B, D. Ventral valves, SMNH Br151265–151267, respectively.A1, B3, view on the external surface;A2, B1, lateral view; A3, oblique lateral view; B2, posterior view. C. Dorsal valve, SMNH Br151268. C1, posterior view; C2, external surface. Scale bar 500 µm.