Parthenina wikanderi, Høisaeter, 2014

Høisaeter, Tore, 2014, The Pyramidellidae (Gastropoda, Heterobranchia) of Norway and adjacent waters. A taxonomic review, Fauna norvegica 34, pp. 7-78 : 18-19

Parthenina wikanderi n.sp.

Figures 13 -15

LSID: urn:lsid:zoobank.org:act:812C0F6A-88DE-47C1-B48C-8F2A64913729

Type material: Holotype ZMBN 99129 .

Typelocality: Aust-Agder, Grimstad, Fevikkilen , 58°22’N, 8°40.9’E, 25 m, fine sand .

Etymology: Named after the tireless mollusk-collector and bivalve specialist, Per Bie Wikander from Grimstad, who is singlehandedly responsible for amassing the large material of microgastropods from the Skagerrak area, and the majority of the material from Nordland county, permitting me to highlight the contrast between the northern and southern pyramidellid fauna in Norway. All specimens of this new species of Parthenina has been collected and sorted out from bottom material by Per Wikander.

Material seen: Norway: Skagerrak , 6 spms, 2 shs. (Holotype ZMBN 99129 ) .

Description: Shell conical, only slightly convex, apical angle 30°-32°. Holotype with four teleoconch whorls, 2.2 x 1.1 mm.Whorls convex, not flatsided. Suture distinct but not canaliculate. Axial ribs straight to slightly curved towards the back, continuing faintly down on the base. The ribs are distinctly wider than the interspaces. Two spiral ribs on body whorl, usually rather obscure, not crossing the axial ribs. Thin, light yellow periostracum, shell underneath chalky white. Protoconch partly intorted, with raised basal edge extending a little outside first teleoconch whorl. Aperture oblong, ovate, spoon-shaped. Umbilicus narrow but distinct. Columellar tooth retracted but fairly strong, sometimes visible in apertural view.

Diagnostic description: Shell: Similar to P. interstincta , but with more evenly rounded, convex whorls, shell wider and more conical, weaker and more rounded axial ribs, and very indistinct spiral ribs. As opposed to P. interstincta , a thin periostracum that flakes off when shell dries. The protoconch is tilted and its base is extending farther outside first teleoconch than that in P. interstincta . Columellar tooth weak, but stronger than in P. interstincta . Soft parts: Not known. Operculum: Not known.

Distribution: So far only found on the Norwegian Skagerrak coast (ZMBN 99129, G 28-71 (2), G 52-71 (2 sh), S 17-87; S 8-88, and S 37-88).

Remarks: Quite a number of species of Chrysallida s.l. have been described from the southern part of the Northeast Atlantic and the Mediterranean, but none of those illustrated in van der Linden & Eikenboom 1992; Peñas et al. 1996; Peñas & Rolán 1998; van Aartsen et al. 2000, or Cachia et al. 2001 seem to fit. Those with a similar sculpture, are all narrower and less conical. The new species might be a variety of the variable P. interstincta , but the specimens of this latter species from the Skagerrak I have seen are all much narrower, more cylindrical. The periostracum also seems to be specific for this new species. A character of possible taxonomic importance is that the sculpture is often partly eroded and faint. The axial ribs are less sharply cut out than in P. interstincta , and are easily ‘destroyed’ when the shell is handled (Figure 14).

Figures

Figure 13. Parthenina wikanderi n.sp., holotype, Fevikkilen, Grimstad, 58°22’N, 8°40.9’E, 25 m, 2.2 mm (ZMBN 99129) Figure 14. Parthenina wikanderi n.sp., holotype, Fevikkilen, Grimstad, 58°22’N, 8°40.9’E, 25 m, 2.2 mm (ZMBN 99129). The top whorls at right from S 37-88. SEM. Figure 15. Comparison between Parthenina wikanderi n.sp. (two specimens at left) and P. interstincta (two at right). To scale, the holotype at left is 2.2 mm long (ZMBN 99129, S 37-88, ZMBN 82355, ZMBN 82305). Figure 16. Spiralinella spiralis, Hillersholmen, Raunefjorden, 60°17.8’ N, 5°11.2’ E, 6-8 m (ZMBN 82405) (left), Hjertøysund, Bodø, 67°17’ N, 14°20’ E, 40-30 m, both 2.2 mm (N 82-76). Figure 17. Spiralinella spiralis, Protoconchs of specimens in Figure 15, three orientations. Figure 18. Spiralinella spiralis, juvenile, three orientations. Figure 19. Spiralinella spiralis, head-foot complex and pigmented mantle organ (not to scale). Figure 20. Spiralinella spiralis, operculum, two views. Scale bar = 200 µm.