Calliostoma valkuri, Cavallari & Salvador & Dornellas & Simone, 2019

Cavallari, Daniel C., Salvador, Rodrigo B., Dornellas, Ana P. S. & Simone, Luiz R. L., 2019, Calliostomatidae, Colloniidae, Margaritidae, and Solariellidae (Gastropoda: Trochoidea) collected by the Marion Dufresne (MD 55) expedition in southeastern Brazil, with description of a new species of Calliostoma, Zootaxa 4609 (3), pp. 401-428 : 409-410

Calliostoma valkuri sp. nov.

( Fig. 4 )

Type material. Holotype MNHN-IM-2000-34300.

Type locality. Brazil, Espírito Santo, off São Mateus, Abrolhos Slope , 19°01’S, 37°47’W, MD55 sta. CB79 , 1500–1575 m (Bouchet, Leal & Métivier leg., 28/v/1987) .

Etymology. The name refers to Valkur, a fictional demigod from the Forgotten Realms campaign setting of the Dungeons and Dragons role-playing game. Valkur is the patron and protector of sailors.

Diagnosis. Teleoconch I very short (0.1 whorl), sculptured by three very delicate spiral cords, beginning and transition to teleoconch II marked by very prominent terminal varices. Teleoconch II sculpture consisting of spiral cords with prominent sharp thorn-like projections; two cords more prominent than remaining cords located on median portion of whorl.

Description. Shell small (H= 4.2 mm, juvenile specimen), trochoid, roughly as tall as wide, with 4 very convex whorls; color homogeneous cream, with nacreous gleam underneath visible by translucency ( Fig. 4 A–C). Spire tall (height ~1/3 of shell height), prominent; spire angle ~60°. Protoconch ( Fig. 4 E, G, H ) prominent, of ~1 whorl (width= 0.4 mm), color indistinct from teleoconchs I/II, surface sculptured by intersected thin lines forming a reticulate pattern of roughly hexagonal shapes; transition marked by conspicuous terminal varix. Teleoconch I ( Fig. 4 G, H ) very short (~0.1 whorl after protoconch), surface sculptured by 3 spiral threads; transition to teleoconch II marked by conspicuous terminal varix. Teleoconch II of ~3½ convex whorls, mainly sculptured by 3–5 spiral cords ( Fig. 4 A, D ), separated by wider interspaces (~3– 4x cord width); ontogeny of cords as follows ( Fig. 4 B, E ): P2 and P3 commencing right after protoconch; P1 commencing at 1.5 teleoconch whorl; S1 commencing at 4.0 whorls; S2 commencing at 4.1 whorls; cords presenting numerous large, spaced, sharp projections resembling rose thorns; two cords, on median region of whorl, more prominent than remaining cords; suture very delicate, nearly indistinguishable ( Fig. 4 G ), not channeled; body whorl sculptured by 5 spiral cords, with 3 larger, dominant cords and two thinner, intercalary cords. Aperture round, prosocline ( Fig. 4 A, D ), height ~1/2 of shell height, cream-colored, nacreous; inner lip slightly flared, forming narrow callus ( Fig. 4 D ). Base convex, sculptured by 8 smooth, wellmarked spiral cords; umbilicus imperforate ( Fig. 4 C, F ); Operculum unknown.

Distribution. Known only from type locality (empty shell).

Measurements. ~4½ whorls, H= 4.1 mm, D= 4.2 mm (holotype).

Material examined. Holotype.

Remarks. A single shell among all the Calliostoma material looked clearly different from the remaining specimens. Among the Western Atlantic congeners, the most similar species is C. militare Ihering, 1907 because both have two strongly marked spiral cords on the median portion of the whorl bearing prominent spikes. The main differences between these species are that C. valkuri sp. nov. has a shorter shell with a less rounded profile, and has conical spikes, as opposed to the rounded ones in C. militare . Other similar species are C. echinatum , C. fascinans Schwengel & McGinty, 1942 , and C. sapidum Dall, 1881 , but the similarity is almost exclusive to the juveniles, due to the spikes on the spiral cords. Nevertheless, the shape of the spikes is much more conical, short and with blunt rounded tips in these species, and all cords display similar width/length, as opposed to the more prominent median cords of C. valkuri sp. nov.

Even without more samples, there are enough characters to easily distinguish it as a new entity. Calliostoma valkuri sp. nov. can be readily told apart from its congeners by two strongly marked spiral cords on the median portion of the whorl bearing prominent spikes resembling rose thorns; subsutural and suprasutural spiral cords similar to the two stronger ones in structure, but much weaker, with less prominent spikes - probably, an adult specimen would have more of such cords, as an increase in the number of cords as the shell grows is seen in nearly all congeners.

Figures

FIGURE 4. Calliostoma valkuri n. sp. Holotype MNHN-IM-2000-34300, sta. DC79 (H=4.1 mm, D=4.2 mm). A. apertural view. B. apical view. C. umbilical view. D. SEM, apertural. E. SEM, apical view. F. SEM, umbilical view. G. SEM, detail of spire. H. SEM, detail of apex showing the protoconch.