Raphitoma obesa, Høisaeter, 2016

Raphitoma obesa View in CoL n.sp.

Figures 2D View Figure 2 , 12 View Figure 12 and 13

h t t p: / / z o o b a n k.o r g / 9 8 E 8 6 E D 3 -2 3 5 C - 41 E 8 - B B2 6 - 458ABE6A5F1C

Clathurella linearis var. pallida F. and H. - Marshall 1912:298 (?)

Raphitoma View in CoL n.sp. - Høisaeter 2009

Type material. Holotype ZMBN 107135 View Materials .

Type locality. Svinestangen , Korsfjorden, Hordaland, Norway, 60°12’N, 5°10’E, c. 100 m. GoogleMaps

Etymology. From Latin obesus, fat. Referring to the shape of the shell.

Material examined. Only the holotype; a specimen from Liholmsrennen, 60°17’N, 5°09’E, 80-95 m (shell destroyed when sample taken for DNA-analysis) GoogleMaps ; a specimen from west of Frøo , Øygarden, 60°35’N, 70–75 m ; one from Mandnesholmen , Nesna, 66°14’N, 65- 63 m ; and one from Lille Hjartøy , Bodø, 67°17’N, 70– 60 m.

Description. Holotype ( Figure 12 View Figure 12 ) 7.0 x 3.6 mm, with five teleoconch whorls. Shell subfusiform with convex whorls and deeply incised sutures. Shell thin, glassy, wide (height 2.1 times the diameter). Spire occupying 34 % of total shell height. Diameter of adapical teleoconch whorl 745– 970 µm. Sculpture of moderately pronounced axial ribs crossed by fairly narrow spiral cords, six cords on penultimate whorl. The axial ribs disappear gradually towards the base. Shell yellowish white with spiral cords usually unpigmented, but sometimes with weak golden brown pigment. The ribs are narrow and separated by a wide ‘valley’, these being from 2 to 2.5 times as wide as the ribs. The rectangles defined by the cords and ribs are twice as wide as high. The surface between the spiral cords densely covered with fine, well separated, microscopic pustules ( Figures 2D View Figure 2 and 12 View Figure 12 ), best observed between spiral cords in upper parts or in juvenile shells. The nodules produced by the crossing of cords and ribs distinct but not very acute, when seen in profile producing a ‘wavy’ aspect. Aperture occupying 47 % of total shell height, aperture width about 41 % of its height. Outer lip slightly undulating with an anal sinus near the suture almost rectangular with a width 90 % of its depth. Usually dense, but not very sharp growth lines between axial ribs ( Figure 12 View Figure 12 ). Siphonal canal moderately long, about 27 % of total shell height. No axial ribs on siphonal canal, but spirals wider and denser together than on the whorls proper. Protoconch with 3.5 to–4 pale, yellowish white whorls (same colour as teleoconch). Protoconch W/L: 0.96. Apical angle c. 50.5°. Apical whorl 160 to 180 µm in diameter. Apical whorl and half of the following with about nine to ten microscopic spiral striae; the next with decussate sculpture, the next with numerous slightly curved axial riblets on top third and delicate decussate grid on bottom two thirds of whorl. Protoconch ending in a weak spiral keel.

Variability. The limited material does not permit a thorough description of morphological variation, but as is evident from Figure 13, a specimen from northern Norway (Figure 13E) is much wider than the three from western Norway (Figures 13A, B, D). The lack of pigment on spiral cords is not absolute, as seen in Figure 13C.

Distribution. So far only found in fjords on the western coast of Norway, 80-100 m depth, mixed bottom material, and at two localities in Nordland county (66°- 67°N, 60-70 m depth). Recently reported from the Kola inlet on the Murman coast of Russia ( Nekhaev 2014, as Raphitoma leufroyi ), based on an empty shell, almost indistinguishable from Figure 13C above.

Remarks. This species was briefly described as Raphitoma n. sp. in Høisaeter (2009). It may have been described (as the variety pallida of R. linearis ) already by Forbes & Hanley (1853:471-472). As several forms of R. aequalis are practically colourless, the description of Forbes & Hanley (1853:472) is too vague to confirm that their ‘variety’ is the same as R. obesa n.sp (“The variety pallida is essentially northern: it is more or less devoid of colouring, has still finer closer and less elevated sculpture, and is even more produced in shape than the richly tinted and prickly southern variety”). Jeffreys (1867:369) merged this ‘variety’ with ‘var. ’ intermedia thus rejecting the existence of a separate ‘colourless’ variety. Marshall fully agrees with Forbes & Hanley in this matter, and objects to Jeffreys’ merging of the two ‘varieties’ to the ‘variety’ aequalis . Marshall’s opinion concerning the status of Var. pallida F. and H. is somewhat equivocal, however, as he equals this variety with var. aequalis Jeff. , while no such equality is claimed for var. intermedia . Anyway, as stated for R. aequalis above, the name pallida is better regarded as a nomen oblitum according to Article 23.9.2 of ICZN.

The most conspicuous difference from R. aequalis is the almost complete lack of colour pattern, and the comparatively wider body whorl. The shell is thinner and almost translucent. The protoconch is invariably of the same hue as the teleoconch (whitish or slightly yellowish), while that of R. aequalis is of a golden yellow-brown hue, sometimes with a whitish apical whorl. Whether it is a good species or not is impossible to conclude based on the available material. Three morphological character states support a specific status, the shape of the shell, the scarcity of shell pigment, and the shape of the columella in fully grown specimens. Also the microsculpture with distinct and well separated pustules on the partly transparent shell support a specific status. In addition the lack of protoconch colour argues for a separate taxon. The considerable variability in the morphology of R. aequalis certainly does not make it easier to decide. All things considered using the name, Raphitoma obesa n.sp. for these five specimens is the best basis for future studies, preferably by molecular methods.