Hyolithellus vladimirovae 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 : 408-411

Hyolithellus vladimirovae Missarzhevsky in Rozanov and Missarzhevsky, 1966

Fig. 68A, C, G .

Material.—Ten fragmentary phosphatic tubes, including SMNH X5969, 5971, 5974, from samples 5a/10.5, 5a/15.5, 5a/17.5, and 5a/34.5 (section 96-5a, Fig. 2 ), Emyaksin Formation, eastern Anabar Uplift, Siberian Platform, Russia. Correlated with the lower part of Cambrian Stage 2.

Description.—Slowly expanding slightly irregularly curved, phosphatic tubes with circular cross-section, 250–750 μm in diameter. External surface covered with low but distinct straight folds, regularly spaced at 100–200 μm and transverse to the longitudinal axis of the tube.

Remarks.—The holotype derives from the middle course of the Lena River at Churan village from sample M42e of the Pestrotsvet Formation ( Dokidocyathus regularis Zone, Tommotian Stage ; Rozanov and Missarzhevsky 1966). The fine longitudinal or transverse striation described by Rozanov and Missarzhevsky (1966) from the type ma-

Fig. 65. Problematic calcium phosphatic sclerites Fomitchella aff. infundibuliformis from early Cambrian Emyaksin Formation, eastern flank of the → Anabar Uplift, Siberia, Russia; samples 5a/10.5 (A, B) and 5a/15 (C), section 96-5a. A–C. SMNH X5951–5953, respectively. A 1, A 3, B 1, B 3, C 2, lateral; A 2, B 2, C 1, apical views; C 3, fibres in outer layer enlarged; C 4, layered wall at the apex, enlarged. Scale bar 12.5 μm (C 3), 25 μm (C 4), and 250 μm (A,

B, C 1, C 2).

terial is not observed on the tubes. Hyolithellus grandis Missarzhevsky in Rozanov et al., 1969 only differs in that is several times larger in size. However, it tends to co-occur with H. vladimirovae , which may justify synonomy of the two forms (Sipin 2001). Hyolithellus isiticus Missarzhevsky in Rozanov et al., 1969 mainly differs in having numerous, well-developed flanges in the later growth stages, compared to a smooth initial part and an intermediate part with moderately high ribs. Thus, the middle part of its conch is, according to Missarzhevsky in Rozanov et al. (1969: 150, 151), similar to H. vladimirovae . The narrower smooth tubes described below may represent ontogenetic variants of H. vladimirovae . The external ornamentation of H. insolitus Grigor’eva in Voronin et al., 1982 (see Kouchinsky et al. 2015a) features weaker concentric ribs, faint longitudinal ridges and furrows that undulate between the ribs.

Stratigraphic and geographic range.— Upper Fortunian– Cambrian Stage 2 of Siberia, Laurentia (as Hyolithellus cf. isiticus in Pyle et al. 2006), Kazakhstan (Missarzhevsky and Mambetov 1981), South China (Steiner et al. 2007), and northern India ( Brasier and Singh 1987: fig. 8.3–8.5).

Figures

Fig. 68. Calcium phosphatic tubes of hyolithelminths Hyolithellus vladimirovae Missarzhevsky in Rozanov and Missarzhevsky, 1966 (A, C, G) and Hyolithellus sp. (B, D, E, F, H, I), from early Cambrian Emyaksin ( A–D, G, I), Medvezhya (E, F), and Kugda-Yuryakh (H) formations, Anabar Uplift, Siberia, Russia; samples 5a/34.5 (A, B), 5a/15.5 (C), 5 a/34.75 (D, I), 5a/10.5 (G), section 96-5a; K2/6 (E, F), K2/60 (H), section 3. A–E. SMNH X5969–5973, respectively. G–I. SMNH X5974–5976, respectively. F. SMNH X5977. Scale bar 500 μm.

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.