Anabarites tristichus 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 : 420

Anabarites tristichus Missarzhevsky in Rozanov et al., 1969

Fig. 76A–C, F .

Material.—Several hundred internal moulds, including figured SMNH X3671, 3672, 6027, from samples 3/12, 3/12.2, K2/25 (section 3, Fig. 3), 5/0 and 5a/34.75 (sections 96-5 and 96-5a, Fig. 2 ), from the Medvezhya and Emyaksin formations, and two celestite-barite replaced tubes with internal moulds, including figured SMNH X3409, from sample K2/26, Medvezhya Formation, Anabar Uplift, Siberian Platform, Russia. Correlated with the upper Fortunian and lower part of Cambrian Stage 2.

Description.—Almost straight, slightly torted tubes with rounded hexagonal aperture. Walls with transverse flanges and thin, shallow growth lines. Three broad, flattened longitudinal lobes separated by shallow depressions. Internal, short protrusions of the wall are impressed into each longitudinal depression and essentially extend as a dashed line on the internal moulds from the apex to the aperture along the three longitudinal depressions ( Fig. 76A, B, F ).

Remarks.— Anabarites tristichus tubes preserved in celestite and barite are discussed by Kouchinsky and Bengtson 2002) and Kouchinsky et al. (2009). The first illustration of anabaritids from Siberia was published by Sysoev (1965: fig. 2) under the name Hyolithellus sp. (recognized by Kouchinsky et al. [2009] as A. tristichus Missarzhevsky in Rozanov et al., 1969). The age of A. tristichus ( Hyolithellus sp. Sysoev [1965: fig. 2]) from “the Atdabanian Horizon” from a locality on the left bank of the Kotuj River, 6 km downstream from the mouth of the Kotujkan River on the western flank of the Anabar Uplift) is questionable. It is not clear from which level of the outcrop the specimen was collected. It probably came from the Kugda-Yuryakh Formation, and, thus, can be correlated with lower part of Cambrian Stage 2.

Stratigraphic and geographic range.— Terreneuvian Series and lower Stage 3; Siberia and Gondwana (South China).

Figures

Fig. 76. Anabaritids from early Cambrian Medvezhya (A–D) and Emyaksin (F, E) formations, Anabar Uplift, Siberia, Russia; samples K2/25 (A, B), K2/26 (C), section 3; 5/0 (F), section 96-5; 5a/34.5 (E), section 96-5a; and 1/29.2 (D), section 1. A–C, F. Anabarites tristichus Missarzhevsky in Rozanov et al., 1969, SMNH X3671 (A; see also Kouchinsky et al. 2009: fig. 26C), SMNH X3672 (B; see also Kouchinsky et al. 2009: fig. 26D), SMNH X3409 (C; see also Kouchinsky and Bengtson 2002: figs. 2, 3 and Kouchinsky et al. 2009: fig. 26A, B), SMNH X6027 (F). A, B, F, lateral views of calcium phosphatic internal moulds; C1, lateral view of celestite-barite replaced tube with calcium phosphatic internal mould; C2, internal protrusion of the wall enlarged; C3, transverse view. D. Anabarites hexasulcatus (Missarzhevsky, 1974), SMNH X6028; D1, lateral; D2, transverse views. E. Anabarites hariolus (Val’kov, 1987), SMNH X3697 (see also Kouchinsky et al. 2009: fig. 36K–M). E1, transverse view of apertural end; E2, E3, lateral views; E4, transverse view of apical end. Scale bar 25 μm (C2), 500 μm (A, B, C1, C3, D–F).

Fig. 2. Composite δ13Ccurve for the Bol’shaya Kuonamka River sections 96-4, 5, and 5a and sampled horizons with fossiliferous samples (arrows with carb numbers). Arrow 4/4 indicates “marker bed with angustiochreids” (Val’kov 1975; Kouchinsky et al. 1999). For section 96-6 see Kouchinsky et al. (2001, 2015a). Shift in stratigraphic column at Manykay–Emyaksin formations contact indicates position of sequence boundary. Stratigraphic ranges and first appearances of fossils (see SOM 1): 1, first appearance of helcionellid molluscs; 2, Oelandiella korobkovi; 3, Securiconus cf. simus; 6, Obtusoconus vostokovae; 7, Obtusoconus cf. mirabilis; 8, Anabarella plana; 13, Aldanella attleborensis; 14, Aldanella cf. sibirica; 22, Purella antiqua; 24, Yunnanopleura accurata; 34, Lopochites sp.; 35, Tianzhushania longa; 37, first appearance of Halkieria sp.; 38, Chancelloria symmetrica; 42, Khetatheca cotuiensis; 44, Conotheca cf. mammilata; 46, Turcutheca sp.; 47, Cupitheca sp.; 50, Orthothecid operculum type C; 51, Protohertzina anabarica; 52, Fomitchella infundibuliformis; 53, Fomitchella aff. infundibuliformis; 54, Fomitchella acinaciformis; 55, Fomitchella aff. acinaciformis; 56, Hyolithellus vladimirovae; 57, Hyolithellus sp.; 60, Selindeochrea cf. tecta; 61, Selindeochrea tripartita; 62, Selindeochrea missarzhevskyi; 63, Selindeochrea ternaria; 64, Anabarites trisulcatus; 65, Anabarites latus; 66, Anabarites natellus; 67, Anabarites kelleri; 68, Anabarites biplicatus; 69, Anabarites tristichus; 70, Anabarites compositus; 71, Anabarites hexasulcatus; 72, Anabarites hariolus; 73, Aculeochrea rugosa; 74, Tiksitheca licis; 75, Cambrotubulus decurvatus; 76, Platysolenites antiquissimus.