Gapparodus bisulcatus ( Müller, 1959 )

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 : 416-418

Gapparodus bisulcatus ( Müller, 1959)

Fig. 56A, C, D .

Material.—Over twenty calcium phosphatic sclerites, including figured SMNH X11236–11238, from samples 19/2B, 19/3B, 19/5B, 19/55, 19/65.5, 19/66.5, upper Erkeket and Kuonamka formations, Khorbusuonka River, Siberia, Russia. Amgan and lower Mayan stages (correlated with the upper part of Cambrian Stage 4–lower Drumian Stage).

Remarks.—Slender, gently curved bilaterally symmetrical calcium phosphatic hollow sclerites with an oval or figureof-eight shaped cross-section extended in sagittal plane. Two longitudinal lateral furrows divide the sclerite into two halves having almost the same width. One with a strongly convex surface and convex in lateral view, whereas the opposite one with a gently convex or flattened surface. Wall with lamellar fibrous composition.

Stratigraphic and geographic range.—Globally distributed and known from Siberia in Cambrian Stage 4 and Wuliuan Stage ( Müller et al. 1995; Kouchinsky et al. 2011, 2015a), ranges from Series 2 through the Furongian Series in South and North China (Dong and Bergström 2001; Babcock et al. 2007; Steiner et al. 2007), Baltica (Bengtson 1976; Müller and Hinz 1991), Gondwana ( Özgül and Gedik 1973; Lee 1975), Laurentia (Clark and Miller 1969; Clark and Robison 1969; Landing 1974; Peel et al. 2016), and Kazakhstan Abaimova and Ergaliev 1975).

Figures

Fig. 56. Sclerites of protoconodonts (A–E) and problematic spines (F–I) from the early and middle Cambrian, Khorbusuonka River, Siberia, Russia; samples 11/2B (B), 19/55 (E), and 19/61 (F–I) from the Erkeket Formation and 19/3B (C) and 19/5B (A, D) from the Kuonamka Formation. A, C. Gapparodus bisulcatus (Müller, 1959), SMNH X 11236 and X11237, respectively.B. Protohertzina sp., SMNH X11240. D. Sclerite tentatively assigned to Gapparodus bisulcatus (Müller, 1959), SMNH X11238.D1, view on the concave side; D2, lateral view.E. Amphigeisina danica (Poulsen,1966), SMNH X11239.F–I. Calcium phosphatic internal moulds of problematic spines with corrugated walls, SMNH X11241–11244, respectively. Scale bar: 500 µm (A–E) and 250 µm (E–I).