Parkula, Bengtson, 1990

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 : 455

Parkula cf. P. esmeraldina Skovsted, 2006

Fig. 31 .

Material.—Two phosphatised opercula, SMNH X 4660 and 4661, from sample K1-3B. Uppermost Emyaksin Formation,

Malaya Kuonamka River; Calodiscus -Erbiella Zone, lower Botoman Stage.

Description.—The operculum has a crescent-shaped dorsal lobe and a strongly convex semi-circular ventral lobe. The dorsal margin is inclined at ca. 90° with respect to the ventral lobe. The dorsal lobe bears blade-like clavicles situated along the margin between two lobes. Cardinal processes diverge at ca. 90º.

Remarks.—The operculum is most similar to Parkula esmeraldina Skovsted, 2006 , which is also different from P. bounites Bengtson in Bengtson et al., 1990 in having more diverged, longer and more dorsally situated cardinal processes. No conchs attributable to Parkula have been found associated with the opercula in our material. Parkula spp. are known from Cambrian Series 2 of Australia ( Bengtson et al. 1990; Gravestock et al. 2001), Antarctica (Wrona 2003), and Laurentia ( Malinky and Skovsted 2004; Skovsted 2006; Skovsted and Peel 2007).

Figures

Fig. 31. Hyolith opercula Parkula cf. P. esmeraldina Skovsted, 2006 from lower Cambrian Emyaksin Formation, Malaya Kuonamka River, Anabar Uplift, Siberia; sample K1-3B. A. SMNH X 4660; inner (A1), oblique ventral (A2), lateral (A3, A4), and dorsal (A5) views. B. SMNH X 4661; lateral (B1), dorsal (B2), and inner (B3) views. Scale bar 300 μm.