Parkula bounites Bengtson

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 : 414-415

Parkula bounites Bengtson in Bengtson et al., 1990

Figs. 51A, B , 52C, E .

Material.—Several phosphatised opercula and probably conchs, including figured SMNH X11207, 11208, 11221, and 11222, from sample 19/33, Erkeket Formation, Khorbusuonka River, and samples 22/50 and 22/67, Sekten Formation, Lena River. Siberia, Russia; upper Toyonian and lower Amgan stages (correlated with the Cambrian Stage 4–lowermost Wuliuan Stage).

Description.—Operculum broadly oval in the plan view, with a crescent-shaped dorsal lobe (cardinal shield) and convex semi-circular ventral lobe (conical shield). The dorsal margin is inclined at ca. 60° with respect to the ventral lobe. Initial part flattened. The dorsal lobe bears short blade-like clavicles situated along the margin between two lobes at edge of conical shield. A single pair of short cardinal processes diverging at ca. 90°.

Remarks.—Fragments of the hyolithid conchs with semi-circular ventral lip occurring in sample 22/50 ( Fig. 53E ) can be attributed to the same species.

Stratigraphic and geographic range.—Cambrian Series 2 of Australia (Bengtson et al. 1990; Gravestock et al. 2001), Antarctica ( Wrona 2003), North China ( Pan et al. 2019), Laurentia ( Malinky and Skovsted 2004; Skovsted 2006b; Skovsted and Peel 2007; Devaere et al. 2019), and Siberia ( Kouchinsky et al. 2015a).

Figures

Fig. 51. Phosphatised hyolith opercula from the lower Cambrian Sekten Formation, lower reaches of the Lena River (A–D) and Erkeket Formation, Khorbusuonka River (E–H), Siberia, Russia; samples 19/10.25 (E, H), 19/11.75 (F, G), and 22/50 (A–D). A, B. Parkula bounites Bengtson in Bengtson et al., 1990, SMNH X11207 and 11208, respectively. C, D. Hyolithid operculum 1, SMNH X11209 and X11210, respectively. E, H. Triplicatella sp., SMNH X11211 and X11212, respectively. F. Majatheca tumefacta Missarzhevsky in Rozanov et al., 1969, SMNH X11213. G. Triplicatella papilio Kouchinsky in Kouchinsky et al., 2015, SMNH X11214. A1, D2, inner surface; B1, C1, E3, H2, outer surface; A2, oblique lateral; B2, C2, D1, E1, H1, lateral; C3, E2, dorsal; and A3, C4, ventral views. Scale bar 500 µm.

Fig. 52. Hyolith conchs from the lower Cambrian Erkeket Formation, Khorbusuonka River (C, D, F–H) and Tyuser (A, B) and Sekten (E) formations, lower reaches of the Lena River, Siberia, Russia; samples 19/12.75 (D, F, G), 19/25.5 (H), 19/33 (C), 21/51 (A, B), and 22/50 (E). A, B, D, F–H. Microcornus cf. eximius Duan, 1984, phosphatised conchs (A, B) and calcium phosphatic internal moulds (D, F, G), SMNH X11215–11220, respectively. C, E. Parkula bounites? Bengtson in Bengtson et al., 1990, phosphatised conchs, SMNH X11221–11222, respectively. B1, C2, D2, F3, oblique apertural, B2, C1, D1, F1, G1, dorsal; and D3, F2, G2, lateral views; E, enlargement showing inner surface of ventral side of a fragmentary conch. Scale bar: 500 µm (A–D, F–H) and 250 µm (E).

Fig. 53. Hyolith conchs Parakorilithes mammillatus He and Pei in He et al., 1984, from the lower Cambrian Erkeket Formation, Khorbusuonka River, Siberia, Russia; sample 19/10.25. A–D. Phosphatised conchs, SMNH X11223–11225, and 11351 respectively. B1, C1, dorsal; B2, D2, lateral; B3, oblique lateral; C2, B4, apertural; and D1, oblique apertural views. Scale bar 250 µm.