Triplicatella papilio Kouchinsky, 2015

Kouchinsky, Artem, Bengtson, Stefan, Clausen, Sébastien & Vendrasco, Michael J., 2015, An early Cambrian fauna of skeletal fossils from the Emyaksin Formation, northern Siberia, Acta Palaeontologica Polonica 60 (2), pp. 421-512 : 452-453

Triplicatella papilio Kouchinsky sp. nov.

Fig. 29A, B .

Ethymology: From Latin papilio , butterfly; for the butterfly-like appearance of the operculum.

Type material: Holotype: SMNH X 4646 ( Fig. 29A ) . Paratype: SMNH X 4647 ( Fig. 29B ) .

Type locality: 70°08.5’N, 114°00’E, Malaya Kuonamka River , left bank at the village Zhilinda , eastern flanks of the Anabar Uplift, northern Siberian Platform .

Type horizon: Uppermost Emyaksin Formation , Calodiscus - Erbiella Zone, lower Botoman Stage, lower Cambrian .

Material.— Several phosphatised opercula, including holotype SMNH X 4646 , from sample K1-3B and paratype SMNH X 4647 , from sample 7/70; uppermost Emyaksin Formation , Malaya Kuonamka and Bol’shaya Kuonamka rivers (respectively); Calodiscus - Erbiella Zone, lower Botoman Stage .

Diagnosis.—Species of Triplicatella with the operculum rounded trapezoidal in plan view and with two prominent folds on the dorsal margin.

Description.—Operculum rounded trapezoidal in plan view, 0.8–1 mm wide, with flattened outer surface. Two prominent and laterally flattened blade-like radial folds of the dorsal surface diverge at ca. 80º, but their bases are perpendicular to the dorsal margin of the operculum ( Fig. 29A 1, B1 ). Invagination of the dorsal margin produces three distinct folds on the outer surface.The folds continue ventrally as two low ridges, which level off towards the margin of the operculum. The ventral part of the operculum has two broad and shallow folds.

Remarks.— Triplicatella Conway Morris in Bengtson et al., 1990 includes three described species, T. disdoma Conway Morris in Bengtson et al., 1990 (type species), T. sinuosa Skovsted, Peel, and Atkins, 2004 , and T. peltata Skovsted, Peel, and Atkins, 2004 . There are also four forms in open nomenclature ( Skovsted et al. 2004). T. papilio sp. nov. is different from other known forms of Triplicatella in having only two inner prominent folds of the dorsal margin.

Stratigraphic and geographic range.—Known only from its type locality and horizon.

Figures

Fig. 29. Hyolith opercula Triplicatella spp. from lower Cambrian Emyaksin Formation, Malaya Kuonamka River and Bol’shaya Kuonamka River, Anabar Uplift, Siberia. A, B. Triplicatella papilio sp. nov. A. SMNH X 4646, holotype, sample K1-3B; dorsal (A1), lateral (A2, A4), inner (A3), and ventral A5, note flattened rounded polygons at the base of the dorsal folds) views. B. SMNH X 4647, paratype, sample 7/70; dorsal (B1) and inner (B2) views. C. Triplicatella sinuosa Skovsted, Peel, and Atkins, 2004; SMNH X 4648, sample B-247; outer (C1), oblique ventral (C2), lateral (C3), and dorsal (C4) views. D. Triplicatella cf. T. peltata Skovsted, Peel, and Atkins, 2004; SMNH X 4649, sample 7/70; dorsal (D1), inner (D2), oblique inner (D3), and lateral D4) views. Scale bar 600 μm, except A1, A5, 300 μm.

Fig. 1. Map showing location of sections 1, 3, Malaya Kuonamka River; 6, 7, Bol’shaya Kuonamka River.