Turcutheca sp.

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

Turcutheca sp.

Fig. 53A, B, D–G .

Material.—Over 20 internal moulds, including figured SMNH X5864, 5865, 5867–5870, from samples 1/25.5, 1/22.5, 1/22, and 1/6 (section 1, Fig. 4 ), K2/60 (section 3, Fig. 3), 5a/34.5 and 5a/34.75 (section 96-5a, Fig. 2 ), Medvezhya, Kugda-Yuryakh, and lower Emyaksin formations, Anabar Uplift, Siberian Platform, Russia. Correlated with the Cambrian Stage 2.

Remarks.—The fossils are represented by phosphatic, smooth and gently bent internal moulds ( Fig. 53A, B, D, E, G ) and phosphatic coatings ( Fig. 53F 1, F 2) of septate conchs with the broadly oval cross-section. They include elongate (up to several cm), slowly expanding conchs with rare oval septa convex towards the apex. From the same horizon as sample K2/60 ( Fig. 53E, G ), from the left bank of the Kotuj River, 6 km downstream the mouth of the Kotujkan River, similar moulds that are larger and have transverse rugae were described by Missarzhevsky (in Rozanov et al. 1969: 108, pl. 1: 8) as Turcutheca rugata (Sysoev, 1959b) .

Figures

Fig. 53. Orthothecid hyoliths Turcutheca sp. (A, B, D–G) and Khetatheca cotuiensis (Sysoev, 1959b) (C), from early Cambrian Emyaksin (A, B, F, H, I ), Medvezhya (C, D), and basal Kugda-Yuryakh (E, G) formations, Anabar Uplift, Siberia, Russia; samples 1/22 (D), section 1; K2/60 (E, G), section 3; 5 a/34.5 (F, H, I) and 5a/34.75 (A, B), section 96-5a; M424/10 (C), section M424. A, B, D–G. SMNH X5864, 5865 (A, B, respectively), SMNH X5867– 5870 (D–G, respectively). A, B, D, E, lateral views of calcium phosphatic internal moulds with transverse septae; F1, lateral view of phosphatic coating of tube fragment with two septae; F2, oblique transverse view of septum near aperture of fragment; G, transverse view of oval septum from apical side of internal mould. C. SMNH X5866, calcium phosphatic internal mould. C1, oblique lateral view of blunt apical end with septum; C2, lateral view of mould with two transverse septae at apical end. H, I. SMNH X5871, 5872, respectively, calcium phosphatic inner coatings of the hyolith conch wall and septae. Transverse views of rounded triangular septum from the apical (H) and apertural (I) sides. Scale bar 500 μm (A, B, I), 1 mm (C–H).

Fig. 4. The δ13Ccurve for Kotuj River section 1and sampled horizons with fossiliferous samples (arrows with numbers). Shift in stratigraphic column carb at Nemakit-Daldyn–Medvezhya formations contact indicates position of sequence boundary. Stratigraphic ranges and first appearances of fossils (see SOM 1): 2, Oelandiella korobkovi; 3, Securiconus cf. simus; 4, Bemella jacutica?; 8, Anabarella plana; 9, Watsonella crosbyi; 10, Pseudoyangtzespira selindeica; 11, Aldanella crassa; 13, Aldanella attleborensis; 15, Philoxenella spiralis; 16, Barskovia hemisymmetrica; 18, Khairkhania cf. evoluta; 19, Ceratoconus striatus; 21, Salanyella cf. costulata; 23, Purella cristata; 25, Yunnanopleura sp.; 26, Obscurania auriculata; 29, Protoconus cf. crestatus; 32, Siphogonuchites triangularis; 34, Lopochites sp.; 37, first appearance of Halkieria sp.; 39, first appearance of Chancelloria sp.; 40, Tianzhushanella sp.; 42, Khetatheca cotuiensis; 46, Turcutheca sp.; 48, Orthothecid operculum type A; 52, Fomitchella infundibuliformis; 57, Hyolithellus sp.; 62, Selindeochrea missarzhevskyi; 63, Selindeochrea ternaria; 64, Anabarites trisulcatus; 67, Anabarites kelleri; 68, Anabarites biplicatus; 71, Anabarites hexasulcatus; 74, Tiksitheca licis; 75, Cambrotubulus decurvatus; 76, Platysolenites antiquissimus; 77, Blastulospongia sp.

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.