Conotheca cf. mammilata 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 : 391

Conotheca cf. mammilata Missarzhevsky in Rozanov et al., 1969

Fig. 52 .

Material.—Four phosphatized conchs, SMNH X5860–5862 and Mo160438 (Kouchinsky 2000b: fig. 2), from samples 5a/34.5 and 5a/34.75 (section 96-5a, Fig. 2 ), Emyaksin Formation, eastern Anabar Uplift, Siberian Platform, Russia. Correlated with Cambrian Stage 2.

Description.—Gently dorso-ventrally curved conchs with circular sross-section, up to several mm long, with transverse growth lines. In dorsal view, apical angle is ca. 15°. Conch wall consists of fibres (microstructure is detailed by Kouchinsky 2000b). These may intensely branch and anastomose, and their typical orientation in the available broken sections is transverse ( Fig. 52C ).

Remarks.—Identical phosphatized conchs occur in the Atdabanian portion of the Emyaksin Formation (sections 96-3 and 96-7; Kouchinsky et al. 2015a: fig. 27A–E, H).

Figures

Fig. 52. Orthothecid hyoliths Conotheca cf. mammilata Missarzhevsky in Rozanov et al., 1969, phosphatized tubes, from early Cambrian Emyaksin Formation, eastern Anabar Uplift, Siberia, Russia; samples 5a/34.5 (A), 5a/34.75 (B–D), section 96-5a. A, B, D. SMNH X5860 (A), SMNH X5861 (B), SMNH X5862 (D). C. SMNH Mo160438 (see Kouchinsky 2000b: fig. 2). A1, A3, B1, B2, C2, D, lateral views; A2, B3, transversal views of apertural end; C1, C3, fibrous microstructure of tubular wall, enlarged. Scale bar 100 μm (C1, C3), 500 μm (A, B, C2, D).

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.