Camenella garbowskae Missarzhevsky

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 : 373-375

Camenella garbowskae Missarzhevsky in Rozanov and Missarzhevsky, 1966

Fig. 22 .

Material.—Several tens of calcium phosphatic sellate and mitral sclerites, including figured SMNH X11006–11017, from samples: 11/18.7, 11/19.5, 11/21.6, 11/28.8. Erkeket Formation, Khorbusuonka River, Siberia, Russia. Dokidocyathus regularis Zone, Tommotian stage (correlated with the upper part of Cambrian Stage 2).

Description.—Sellate sclerites ( Fig. 22G–J, L ) asymmetrical, up to 1.2 mm long and wide in planar view. Sella, a deep longitudinal depression, 1/4 to 1/3 of the sclerite width, divides sclerites into larger and smaller lobes. The larger lobe is higher, approximately twice as long and more than four times the width of the smaller lobe and carries 10–15 variously expressed radial ridges. Smaller lobe ornamented with longitudinal striations. Co-marginal folds well expressed on the dorsal surface of sclerites. Apex slightly coiled. Duplicature adpressed to the inner surface near the apex. Inner surface of sclerites smooth with gently expressed co-marginal folds.

Mitral sclerites ( Fig. 22A, B, E ) asymmetrical pyramidal, up to 1 mm long, from apex to the aperture and up to 1.2 mm wide, covered with distinct concentric growth lines. Obplicate side carries several faint radial ridges and striation see description of morphological terms in Kouchinsky et al. 2015a: comments to fig. 37A). Plicate side with four prominent radial ridges. Accrescent and decrescent sides without radial ridges. Apex slightly inclined over the decrescent side.

Remarks.—For emended diagnosis and discussion of the Camenella see Bengtson (1986) and Skovsted et al. (2009). For emended diagnosis of C. garbowskae see Kouchinsky et al. (2015a).

Sellate sclerites with a flared margin ( Fig. 22D ) identical to Camenella cf. C. garbowskae in Kouchinsky et al. (2015a: fig. 39) may well also belong to the C. garbowskae scleritome.

Camenella aff. C. garbowskae Missarzhevsky, 1966 in Rozanov and Missarzhevsky, 1966 ( Fig. 22K ) is represented by a single dextral sellate sclerite from sample 11/28.8. The sclerite has five prominent radial ribs and distinct commarginal folds.Similar sclerites are described from the Tommotian and Atdabanian stages of Siberia, from the Emyaksin and Tyuser formations ( Rozanov and Missarzhevsky 1966: pl. 13: 11–12; Rozanov et al. 1969: 169; Kouchinsky et al. 2015a: fig. 43). Planiform mitrals ( Fig. 22F ), similar to Camenella plana (Missarzhevsky in Rozanov et al., 1969) known to co-occur with C. garbowskae and can probably be included in C. garbowskae scleritome (Bengtson 1986; Kouchinsky et al. 2015a).

Stratigraphic and geographic range.—Tommotian stage, Siberia, Russia.

Family Lapworthellidae Missarzhevsky in Rozanov and Missarzhevsky, 1966

Genus Lapworthella Cobbold, 1921

Type species: Lapworthella nigra Cobbold, 1921 ; Callavia Zone , lower Cambrian; Comley, Shropshire, Avalonian Britain.

Figures

Fig. 22. Tommotiid Camenella Missarzhevsky in Rozanov and Missarzhevsky, 1966 from the lower Cambrian Erkeket Formation, Khorbusuonka River, Siberia, Russia; samples 11/19.5 (A, E, G), 11/18.7 (B), 11/21.6 (C, D, F, H, I, J, L), and 11/28.8 (K). A, B, E. Camenella garbowskae Missarzhevsky in Rozanov and Missarzhevsky, 1966, mitral sclerites, SMNH X11006–11008, respectively. F. Camenella plana (Missarzhevsky in Rozanov et al., 1969), mitral sclerite SMNH X11009, tentatively synonymized with C. garbowskae. C, G–J, L. Camenella garbowskae Missarzhevsky in Rozanov and Missarzhevsky, 1966, sellate sclerites, SMNH X11010–11015, respectively. D. Camenella cf. C. garbowskae, sellate sclerite, SMNH X11016. K. Camenella aff. C. garbowskae, sellate sclerite, SMNH X11017. Scale bar: 500 µm (A–D, F–I, K, L) and 1 mm (E, J).