Linevitus? minutus Missarzhevsky

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 : 454-455

Linevitus? minutus Missarzhevsky in Rozanov and Missarzhevsky, 1966

Fig. 27G, J .

Material.— Single specimen from sample 7/30, three specimens, including SMNH X 4657 , from sample 7/31.5 and four specimens from sample 7/31.9; correlated with the Delgadella anabara Zone, Atdabanian Stage. One specimen, SMNH X 4658 , from sample 7/70; Calodiscus - Erbiella Zone, lower Botoman Stage. Emyaksin Formation, Bol’shaya Kuonamka River .

Description.—Conch straight sided, with a sub-triangular cross-section. Dorsal surface rounded in the middle, with flanks dipping towards rounded lateral longitudinal ridges, grading into a slightly convex ventral surface. In dorsal view, the apical angle is ca. 30°. The conch is covered with transverse growth lines slightly curved towards the apex on dorsum. On venter, the growth lines are strongly curved towards the aperture and parallel with the edge of a long semi-circular ligula. Growth lines produce small lateral sinuses.Apical end not preserved.

Remarks.—This is very similar to the holotype of Linevitus minutus Missarzhevsky illustrated by Rozanov and Missarzhevsky (1966: 108, pl. 11: 7, 8; John Malinky, personnal communication in 2008), from the Tommotian Stage of Siberia. The curvature towards dorsum seen in the species is not apparent in the fragments available. The fossils are also similar to Hyolithida indet. 3 ( Kouchinsky et al. 2011: fig. 11G–I).

Figures

Fig. 27. Hyolith conchs from lower Cambrian Emyaksin Formation, Bol’shaya Kuonamka River and basal Kuonamka Formation, Malaya Kuonamka River, Anabar Uplift, Siberia. A–E, H. Conotheca cf. C. mammilata Missarzhevsky in Rozanov et al., 1969. A. SMNH X 4623, sample 7/29; longitudinal view on presumably dorsal side. B. SMNH X 4621, sample 7/27.5; longitudinal view on presumably dorsal side. C. SMNH X 4622, sample 7/27.5; longitudinal view. D. SMNH X 4663, sample 7/30; D1, transversal view from the apertural end; D2, longitudinal view. E. SMNH X 4620, sample 3/65; lateral (E1) and dorsal (E2) views. H. SMNH X 4624, sample 7/31.5; longitudinal view. F. Conotheca circumflexa Missarzhevsky in Rozanov et al., 1969, SMNH X 4629; F1, oblique longitudinal view showing transversal section; F2, longitudinal view. G, J. Linevitus? minutus Missarzhevsky in Rozanov and Missarzhevsky, 1966. G. SMNH X 4657, sample 7/31.5; lateral (G1), dorsal (G2), and apertural (G3) views. J. SMNH X 4658, sample 7/70; ventral side with growth increments. →