Botsfordia caelata (Hall, 1847)

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 : 365-368

Botsfordia caelata (Hall, 1847)

Fig. 14 .

Material. —Over one hundred calcium phosphatic dorsal and ventral valves, including figured SMNH Br151240– 151248, from samples K1/5B, K1/7B, 1/7.8, 1/9, 7/70, 8/23.1, 8/32, upper Emyaksin and Kuonamka formations, Bol’shaya Kuonamka and Malaya Kuonamka rivers, samples 19/3.25, 19/10.25, 19/1B, 19/2B, Erkeket Formation, Khorbusuonka River, Siberia, Russia. Botoman to lower Mayan stages (correlated with the Cambrian Stage 4–lower Drumian Stage).

Description.— Shell biconvex flattened, rounded in outline, up to 4 mm long and wide, with slightly undulating growth lines. Numerous tubercles ca. 1 μm in diameter, arranged along the concentric growth lines developed on the surface of adult shell. In larger specimens radial costellae are present. Brephic shell oval, 350–400 μm long and 450–500 μm wide, distinctly separated from the adult shell by a halo. Brephic shell surface with numerous tiny pits, ca. 1 μm in diameter. Ventral brephic valve bears a tubercle near umbo and two low tubercles situated anteriorly. Dorsal brephic valve with a pair of distinct tubercles at the posterior margin and respective elevations situated anteriorly. Ventral valve has developed propareas, short pseudointerarea divided by delthyrium, which forms a pedicle opening. Dorsal valve with a narrow pseudointerarea and divided by a low median septum.

Remarks.— See comparative discussion in Ushatinskaya and Korovnikov (2016).

Stratigraphic and geographic range.— Cambrian Stage 4– lower Drumian Stage, Siberian Platform and Laurentia.

Family Acrothelidae Walcott and Schuchert in Walcott, 1908

Genus Acrothele Linnarsson, 1876

Type species: Acrothele coriacea Linnarsson 1876 ; middle Cambrian ; Sweden .

Acrothele olenekensis Pelman in Pelman and Pereladov, 1986

Fig. 15 .

Material.— Over one hundred calcium phosphatic dorsal and ventral valves, including figured SMNH Br151249–151253, from samples 19/43.25, 19/52, 19/55, 19/65.5, 19/66.5, 19/66.75, 19/2B, 19/5B, 19/6B, Erkeket and Kuonamka formations, Khorbusuonka River, samples 1/22 and 8/18.5, Kuonamka Formation, Malaya Kuonamka and Bol’shaya Kuonamka rivers, Siberia, Russia. Amgan and lower Mayan stages (correlated with the Cambrian Stage 4–lower Drumian Stage).

Description.— Shell slightly biconvex flattened, rounded in outline, with coarse concentric growth lines. Numerous tubercles ca. 1 μm in diameter are scattered on the surface of adult shell. Ventral valve with anterior position of umbo relative to the posterior margin. Brephic shell broadly oval, 400– 500 μm long and 550–600 μm wide, distinctly separated from the adult shell by a halo. Brephic shell surface with numerous tiny pits, a few μm in diameter. Marginal umbo of dorsal valve. Ventral brephic valve with a sub-rectangular elevated, 50–80 μm wide foramen contacting the adult shell. Two distinct tubercles situated anteriorly. Dorsal brephic valve with one pair of prominent tubercles at the posterior margin and another pair of less prominent tubercle situated anteriorly. Pseudointerarea pass gradually into the lateral margins of ventral valve. Dorsal valve with a narrow pseudointerarea, short and narrow propareas. Median septum low.

Remarks.— See the comparative study in Ushatinskaya and Korovnikov (2016).

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

Class Paterinata Williams, Carlson, Brunton, Holmer, and Popov, 1996

Order Paterinida Rowell, 1965

Family Paterinidae Schuchert, 1893

Genus Pelmanotreta Skovsted, Ushatinskaya, Holmer, Popov, and Kouchinsky, 2014

Type species: Cryptotreta neguertchenensis Pelman, 1977 ; upper Tommotian stage (Cambrian Stage 2); Siberian Platform, Russia. Pelmanotreta neguertchenensis ( Pelman, 1977)

Fig. 16 .

Material.—Fifty fragmentary and complete calcium phosphatic dorsal valves and fragments of ventral valves, including figured SMNH Br151254–151258, from samples 3/23, 3/25B, 3/34, 7/16, 7/20, 7/22.6B, 7/25.5, 7/25.6, 7/27.5, Emyaksin Formation, Malaya Kuonamka and Bol’shaya Kuonamka rivers and sample 11/28.8, Erkeket Formation, Khorbusuonka River. Siberia, Russia; Dokidocyathus lenaicus –Tumuliolynthus primigenius Zone, Tommotian stage (correlated with the upper part of the Cambrian Stage 2)– Repinaella Zone, Atdabanian stage (correlated with the Cambrian Stage 3).

Description.—Dorsal valves, up to 5 mm wide, semicircular in outline, slightly convex, with broad and shallow sulcus, fine concentric growth lines, interrupted by radially oriented series of nick points. A narrow interarea situated along the entire posterior margin. Interior surface with radiating imprints of pinnate mantle canals. Dorsal brephic shell semicircular, ca. 200 μm long and 300 μm wide, with radial folds.

Remarks.—See Skovsted et al. (2015) for discussion of this species and genus.

Stratigraphic and geographic range.— Dokidocyathus regularis Zone, Tommotian stage (correlated with the upper part of Cambrian Stage 2)– Nochoroicyathus kokoulini Zone, Atdabanian stage (correlated with the Cambrian Stage 3), Siberian Platform.

Figures

Fig. 14. Lingulid brachiopod Botsfordia caelata (Hall, 1847) from the Cambrian Emyaksin (F, G) and Kuonamka (A–E, H, I) formations, Malaya Kuonamka and Bol’shaya Kuonamka rivers, Siberia, Russia; samples K1/7B (A, B, H) and 1/9 (C–E, I) and 7/70 (F, G). A, B, F. Ventral valves, SMNH Br151240–151242, respectively.A1, A3, B2, close-ups showing brephic shell. C, D, G–I. Ventral valves, SMNH Br151243–151247, respectively. D2, enlargement showing brephic shell. E. Deformed specimen with both valves preserved, SMNH Br151248, view on the ventral valve. Scale bar: 1 mm (A2, B1, C, D1, E–I) and 250 µm (A1, A3, B2, D2).

Fig. 15. Lingulid brachiopod Acrothele olenekensis Pelman in Pelman and Pereladov, 1986 from the middle Cambrian Kuonamka Formation, Malaya Kuonamka and Bol’shaya Kuonamka rivers,Siberia,Russia; samples 1/22 (A, B, D), K1/17B (C), and 8/18.5 (E).A, B, D. Ventral valves, SMNH Br151249– 151251, respectively. A2, A3, close-ups showing brephic shell; D2, enlargement showing pits on the surface of brephic shell. C, E. Dorsal valves, SMNH Br151252 and 151253, respectively. E, dorsal valve of the brephic shell. Scale bar: 1 mm (A1, C, D1), 500 µm (B), 250 µm (A2, A3, E), and 25 µm (D2).

Fig.16. Paterinid brachiopod Pelmanotreta neguertchenensis (Pelman,1977) from the lower Cambrian Emyaksin Formation, Bol’shaya Kuonamka River, Siberia, Russia; sample 7/27.5. A–E. Dorsal valves, SMNH Br151254–151258, respectively.A2,close-up of the brephic shell. Scale bar: 1 mm (A1, C–E) and 250 µm (A2, B).