Anabarites trisulcatus Missarzhevsky

Kouchinsky, Artem, Bengtson, Stefan, Landing, Ed, Steiner, Michael, Vendrasco, Michael & Ziegler, Karen, 2017, Terreneuvian stratigraphy and faunas from the Anabar Uplift, Siberia, Acta Palaeontologica Polonica 62 (2), pp. 311-440 : 417-419

Anabarites trisulcatus Missarzhevsky in Voronova and Missarzhevsky, 1969

Fig. 74A–F, H, I, K .

Material.—Several hundred fragmentary tubes and internal moulds, including figured SMNH X6002–6007, 6009, 6010, 6012, from samples 4/4, 1/C, 2/4, K1b/8, K1b/10, K1b/13, 2/7, and M419/12 (section 2, Fig. 1), Manykay and Nemakit-Daldyn formations, Anabar Uplift, Siberian Platform, Russia. Correlated with the Fortunian Stage.

Description.—Irregularly curved, slowly expanding tubes with triquetrous transverse profile. Three rounded lobes are separated by narrow and shallow grooves that are commonly distinctively defined on the internal and external surfaces of the tube. Thin transverse growth lines curve towards the aperture in the grooves and form wedge-like protrusions of the aperture ( Fig. 74E ).

Remarks.—Distinct wedge-like protrusions are observed among the type material from the Nemakit-Daldyn Formation. Specimens from the Medvezhya and Emyaksin formations have an apparently straight apertural margin and may represent, therefore, different species (see remarks on Anabarites cf. trisulcatus by Kouchinsky et al. 2009: 257).

→ Fig. 72. Anabaritid Selindeochrea missarzhevskyi (Vasil’eva, 1986) from early Cambrian Medvezhya (A, F) and Emyaksin (B–E) formations, Anabar Uplift, Siberia, Russia; samples 1/28.5 (A, F), section 1; and 5a/34.75 (B–E), section 96-5a. A–E. SMNH X5992–5996, respectively; calcium phosphatic internal moulds. A 1, B 2, C 1, D, E, lateral views; A 2, transverse view of apertural end; B 1, C 2, transverse views of apical end. F. SMNH X5997, calcium phosphatic external mould; F 1, oblique transverse; F 2, lateral; F 3, transverse views. Scale bar 500 μm.

Internal moulds of Anabarites aff. trisulcatus ( Fig. 74Q, R ) from the Medvezhya Formation differ from the topotypes of A. trisulcatus in having broader, shallow longitudinal grooves. Growth lines are not expressed on the available internal moulds (see SOM 1 for other species associated with Anabarites aff. trisulcatus ).

The limited number of distinctive features and difference in preservation of the tubes makes recognition of Anabarites trisulcatus and the distinction of potentially close species difficult. Several other forms of Anabarites co-occur in the upper Manykay Formation at the Bol’shaya Kuonamka River (sample 96-4/4; see also descriptions in Kouchinsky et al. 2009; SOM 1). These named species include rapidly expanding Anabarites latus Val’kov and Sysoev, 1970 ( Fig. 74M ) and Anabarites natellus Val’kov and Sysoev, 1970 ( Fig. 74P ) with rounded hexagonal cross-section.

Stratigraphic and geographic range.— The species is questionably reported (see discussion on carbon isotope trends above) from the uppermost Ediacaran of the Siberian Platform, occurs through the Terreneuvian Series worldwide and ranges into Cambrian Stage 3 of the Siberian Platform, South China and Tarim (see Kouchinsky et al. 2009, 2015a and references therein).

Figures

Fig. 74. Anabaritids from early Cambrian Nemakit-Daldyn (A–F, H, I, K, L, N), Manykay (G, M, P), Medvezhya (Q, R), and Emyaksin (J, O) formations, Anabar Uplift, Siberia, Russia; samples 2/7 (A, B, K), K1b/10 (C), M419/12 (D–F, H, I), 1282 (L, N), section 2; 1/29.2 (Q, R), section 1; 4/4 (G, M, P), 5/0 (O), and 5a/34.75 (J), from sections 96-4, 96-5, and 96-5a, respectively. A–F, H, I, K. Anabarites trisulcatus Missarzhevsky in Voronova and Missarzhevsky, 1969, SMNH X6002–6007 (A–F, respectively), SMNH X6009 (H), SMNH X6010 (I), SMNH X6012 (K), phosphatized tubes with internal moulds. A–D, I, K, lateral views; E, lateral view of apertural region; F, transverse view; H, apertural fragment of relatively large tube. G, J, L, N. Anabarites cf. trisulcatus, SMNH X6008 (G), SMNH X6011 (J), SMNH X6013 (L), SMNH X6015 (N), internal moulds, lateral views. M. Anabarites latus (Val’kov and Sysoev, 1970), SMNH X6014, lateral view. O. Anabarites cf. signatus Mambetov in Missarzhevsky and Mambetov, 1981, SMNH X6016, lateral view. P. Anabarites natellus (Val’kov and Sysoev, 1970), SMNH X6017, transverse view of etched external mould;. Q, R. Anabarites aff. trisulcatus Missarzhevsky in Voronova and Missarzhevsky, 1969, SMNH X6018, 6019, respectively; calcium phosphatic internal moulds, lateral views. Scale bar 250 μm (E, I), 500 μm (A–D, G, H, J, L, N–P), 1 mm (F, K, M, Q, R).