Anabarites tristichus 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 : 433-434

Anabarites tristichus Missarzhevsky in Rozanov et al., 1969

Fig. 67A .

Material.—Single calcium phosphatic internal mould, SMNH X11315, from sample 11/16.05, basal Erkeket Formation, Khorbusuonka River, Siberia, Russia. Dokidocyathus regularis Zone, Tommotian stage (correlated with the upper part of Cambrian Stage 2).

Remarks.—Represented by a gently curved internal mould replicating lumen of a tube. Three radially symmetrical longitudinal rows of elongated notches are situated in shallow depressions between flattened convex lobes. Faint replicas of parallel growth lines run transversally. See Kouchinsky et al. (2009) for additional description and discussion.

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

Anabarites hexasulcatus ( Missarzhevsky, 1974) Fig. 67B .

Material.—Single calcium phosphatic internal mould, SMNH X11316, from sample 15/23, Chuskuna Formation (upper part of the Kessyusa Group), Khorbusuonka River, Siberia, Russia. Watsonella Zone, Cambrian Stage 2.

Remarks.—Fragment of internal mould with six longitudinal lobes and radially symmetrical cross-section, ca. 0.5 mm in diameter. Rounded lobes delimited by alternating deeper first- and shallower second-order longitudinal furrows.

Stratigraphic and geographic range.—Uppermost Fortunian and lower part of Cambrian Stage 2, Siberian Platform

Russia), western Mongolia (Esakova and Zhegallo 1996: 96, pl. 3.17), and probably South China ( Kouchinsky et al. 2009).

Anabarites korobovi (Missarzhevsky in Rozanov and Missarzhevsky, 1966)

Fig. 67E, F .

Material.—Several hundred calcium phosphatic internal moulds, including SMNH X11319 and 11320 figured herein and those illustrated by Kouchinsky et al. 2009: fig. 37, from samples 11/2B, 11/16.05, and 11/16.1, basal Erkeket Formation, Khorbusuonka River, Siberia, Russia. Dokidocyathus regularis Zone, Tommotian stage (correlated with the upper part of Cambrian Stage 2).

Remarks.—Represented by internal moulds gently curved in one plane, slowly expanding with rounded triangular cross-section, covered with straight transverse growth lines. The type material in Rozanov et al. (1966) is described from the Chekurovka locality in lower reaches of the Lena River, ca. 60 km upstream from the Ulakhan-Ald’yarkhay sections. Beyond Siberia, such forms are reported from the Cambrian Stage 2 of South China and Avalonia (see Kouchinsky et al. 2009).

Stratigraphic and geographic range.— Nochorojcyathus sunnaginicus and Dokidocyathus regularis zones of the Tommotian stage (correlated with the upper part of Cambrian Stage 2), Siberian Platform, Russia; Cambrian Stage 2, Avalonia ( Landing 1988).

Figures

Fig. 67. Anabaritids, internal moulds (A–F) and other problematic tubes G–I) from the lower Cambrian Kessyusa Group (B–D, H, I) and Erkeket Formation (A, E–G), Khorbusuonka River, Siberia, Russia; samples 11/16.05 (A), 11/2B (E, F), 15/23 (B–D, H, I), and 20/1B (G). A. Anabarites tristichus Missarzhevsky in Rozanov et al., 1969, SMNH X11315. A1, transversal view of the tube; A2, lateral view. B. Anabarites hexasulcatus (Missarzhevsky, 1974), SMNH X11316. C. Selindeochrea ternaria Missarzhevsky inRozanov etal.,1969),SMNHX11317.D.Cambrotubulus sp., SMNH X11318.E, F. Anabarites korobovi (Missarzhevsky in Rozanov and Missarzhevsky, 1966), SMNH X11319 and 11320, respectively. G. Coleolella billinsi (Sysoev, 1962), SMNH X11321. H, I. Platysolenites antiquissimus Eichwald, 1860, SMNH X11322 and 11323, respectively. Scale bar: 250 µm (A) and 500 µm (B–I).