Tianzhushanella 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 : 386

Tianzhushanella sp.

Fig. 48 .

Material.—Four internal moulds SMNH X5834, 5835, 5837, 5838, from samples 1/22 (section 1, Fig. 4 ), K1a/67 (section 2, Fig. 1), and K2/60 (section 3, Fig. 3), from the Medvezhya and Kugda-Yuryakh formations, western Anabar Uplift; and SMNH X5836, from sample M71-2/62, from the upper Kessyusa Formation, Olenyok Uplift, Siberian Platform. Correlated with lower part of Cambrian Stage 2.

Description.—Bilaterally symmetrical shell with broad oval aperture and submarginal apex. Subapical margin of aperture is broadly and strongly arched. Inner surface of apical area has a pair of radially elongated, closely spaced, bilaterally symmetrically situated cavities replicated by a pair of spine-like protrusions on the internal mould ( Fig. 48C ). The elevated median part of the inner surface near the apex is covered with polygonal imprints, whereas larger imprints occur distally ( Fig. 48E ).

Figures

Fig. 48. Stem-group brachiopod? Tianzhushanella sp., internal moulds, from early Cambrian Medvezhya (A, B) and Kugda-Yuryakh (D, E) formations, western Anabar Uplift, Siberia, Russia; samples 1/22 (A, B), section 1; K2/60 (D), section 3; and K1a/67 (E), section 2; and upper Kessyusa Formation, Olenyok Uplift, Siberia, Russia, sample M71-2/62 (C). A–E. SMNH X5834–5838, respectively. A1, B3–D3, E1, upper; A2, B2–E2, subapical; A3, B1, C1, D4, lateral views; D1, subapical area enlarged; E3, supra-apical proximal area with tubercles enlarged; E4, polygonal texture on surface of mould. Scale bar 50 μm (E3), 100 μm (D1, E4), 500 μm (A–C, D2–D4, E1, E2).

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.