Dabashanites mirus Chen, 1979

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 : 382

Dabashanites mirus Chen, 1979

Fig. 44B .

Material.—Single phosphatized sclerite SMNH X5792 from sample 1282 (section 2, Fig. 1), upper Nemakit-Daldyn Formation, western Anabar Uplift, Siberia, Russia. Correlated with the upper Fortunian Stage.

Description.—Aggregate (1 mm long and ca. 0.4 mm wide) of closely spaced, hollow, blade-like sclerites that gradually merge along their basal parts. Base of the merged group is rectangular in cross-section. Distal parts of the sclerites are gently curved. Sclerites display inner longitudinal fibrosity and transverse striation on the surface.

Remarks.—Steiner et al. (2004a) synonymized Dabashanites with Siphogonuchites . Dabashanites differs, however, from other siphogonuchitids in being composed of merged sclerites with a common base. Dabashanites may actually be a central branched sclerite of a Siphogonuchites -scleritome. We maintain Dabashanites as a separate taxon until the association of siphogonuchitid sclerites and branched Dabashanites is demonstrated. Dabashanites lemidiensis Kerber, 1988 , from the upper Fortunian–lower part of Cambrian Stage 2 of France probably represents a fragment of a Maikhanella -like scleritome. A certain degree of similarity exists between fused sclerites of Dabashanites and the blind canals that surround the lumen in the sclerites of halkieriid Thambetolepis ( Bengtson et al. 1990) . Ontogenetically merged siphogonuchitid sclerites and cap-like shells composed of merged sclerites support the suggestion that the sclerites and shells may have belonged to the same organism Bengtson 1992).

Stratigraphic and geographic range.— Upper Fortunian Stage of Siberia ( Purella Zone ), South China ( Anabarites trisulcatus – Protohertzina anabarica Assemblage Zone ; see Chen 1979; Steiner et al. 2004a); occurrence in the Paragloborilus subglobosus – Purella squamulosa Assemblage Zone of Meishucunian Stage of South China mentioned by Parkhaev and Demidenko (2010) but may reflect reworking. Also occurs in western Mongolia ( Mongolodus rostriformis and Halkieria amorpha – Tianzhushania tetramera zones; Esakova and Zhegallo 1996), and Iran (Middle Dolomite Member, Soltanieh Formation, Elborz Mountains; Hamdi 1995).

Figures

Fig. 44. Siphogonuchitid sclerites from early Cambrian Nemakit-Daldyn Formation of western Anabar Uplift, Siberia, Russia; samples K1a/43 (A), 1282 (B), K1a/36A (C), 2/A (D, E, G), and K1a/47 (F, H–J) from section 2. A, D–G. Siphogonuchites subremualis (Bokova, 1985), calcium phosphatic internal moulds, SMNH X5791 (A), SMNH X5794–5797 (D–G, respectively). A1, oblique lateral view of basal part of articulated sclerite group; A2, lateral view of sclerites; D1, view of lower surface of sclerite; D2, lateral view; E1, view of upper surface at distal end; E2, transversal view; G1, G2, views of lower side of basal part of sclerite. B. Dabashanites mirus Chen, 1979, group of articulated phosphatized sclerites, SMNH X5792; B1, B2, oblique lateral views. C. Siphogonuchites triangularis Qian, 1977; pyritised internal mould in lateral view, SMNH X5793. H–J. Tianzhushania longa Qian, Chen, and Chen, 1979; calcium phosphatic internal moulds, SMNH X5798–5800, respectively; H, J, lateral; I, transverse views. Scale bar 250 μm (A), 500 μm (B, D1, E–J), 1 mm (C, D2).