Pyrgopolon decorata ( Stolley, 1912 )

Vinn, Olev, Hryniewicz, Krzysztof, Little, Crispin T. S. & Nakrem, Hans A., 2014, A Boreal serpulid fauna from Volgian-Ryazanian (latest Jurassic-earliest Cretaceous) shelf sediments and hydrocarbon seeps from Svalbard, Geodiversitas 36 (4), pp. 527-540 : 531-532

? Pyrgopolon decorata ( Stolley, 1912)

( Fig. 3 A-C)

Ditrupa decorata Stolley, 1912: 23-26 , pl. 2, figs 5, 6, pl. 3.

Serpula (Cycloserpula) cf. subcrispa Parsch, 1956: 28, pl. 21, fig. 3. — Birkenmajer et al. 1982: 118, pl. 38, fig. 7.

MATERIAL AND LOCALITY. — see Table 1.

DESCRIPTION

Tubes curved, with circular cross section.Tube wall rather thick, 0.7 mm at tube diameter 3.2 mm.

Entire tube covered with extremely regular fine perpendicular rings, 8 to 9 per 1 mm at tube diameter of 5.0 mm. Several weakly developed thin, but regularly shaped ampullacea-type peristomes present, about 0.5mm wide.Tube double-layered, with chevron-shaped growth lamellae.

DISCUSSION ffle specimens are assigned to? P. decorata , due to their characteristic fine perpendicular tube ornamentation.? Pyrgopolon decorata is a serpulid because of the chevron-shaped growth lamellae, and we tentatively ascribe this species to the genus Pyrgopolon because of its relatively thick walled and large tubes.? Pyrgopolon decorata differs from? P. aff. nodulosum by the presence of fine regular perpendicular ornamentation.? Pyrgopolon decorata differs from? Pyrgopolon sp. A in having fine regular perpendicular ornamentation and ampullacea-type peristomes.

? Pyrgopolon aff. nodulosum ( Lundgren, 1883) ( Fig. 3 D-G)

Dentalium nodulosum Lundgren, 1883: 10 , 11, pl. 2, figs 7-9.

Serpula sp. indet. – Birkenmajer et al. 1982: 119, pl. 38, fig. 8; pl. 43, fig. 8.

MATERIAL AND LOCALITY. — See Table 1.

DESCRIPTION

Tube smooth, cross section circular, straight, with weakly developed regularly shaped ampullacea-type peristomes, about 1 mm wide.Tube wall moderately thick, about 0.5 mm at 3.0 mm tube diameter of free tube part, two-layered, inner layer granular, outer layer prismatic; relative thickness difficult to estimate due to corrosion. Chevron-shaped growth lamellae visible.

DISCUSSION ffle specimens presumably belong to Dentalium nodulosum Lundgren, 1883 , because they have a similar general appearance and lack of fine perpendicular ornamentation. Dentalium nodulosum is a serpulid, not a scaphopod, because of the chevronshaped growth lamellae. ffle species is tentatively assigned to the genus Pyrgopolon because of the relatively large tubes.

Figures

FIG. 3. — Serpulids from background sediments and seep carbonate bodies,Spitsbergen,Svalbard: A-C,?Pyrgopolon decorata (Stolley, 1912): A, two large specimens showing the shape and external ornament of the tube (PMO 217.355A, B), Konusdalen; B, details of the external ornament of?Pyrgopolon decorata (PMO 317.355 A); C, acetate peel of the tube wall of?Pyrgopolon decorata (PMO 217.355 B). D-G,?Pyrgopolon aff. nodulosum (Lundgren, 1883): D, fragment of a tube (PMO 217.357), seep 3; E, acetate peel of the tube wall (PMO 217.357), seep 3; F, mass accumulation of?Pyrgopolon aff. nodulosum (PMO 226.601), Echinoderm bed, Janusfjellet; G, thin section of the tube wall of?Pyrgopolon aff. nodulosum (PMO 214.847), Echinoderm bed, Janusfjellet. Scale bars: A, 5 mm; B, 1 mm; C, E, G, 200 µm; D, 2 mm; F, 15 mm.