Drymaeus (Drymaeus) rex, Breure, Abraham S. H., 2009

Breure, Abraham S. H., 2009, New Orthalicidae (Mollusca, Gastropoda) from Venezuelan Guayana: unravelling secrets from the Lost World, Zootaxa 2065, pp. 25-50 : 41-43

publication ID	https://doi.org/ 10.5281/zenodo.186920
DOI	https://doi.org/10.5281/zenodo.5618382
persistent identifier	https://treatment.plazi.org/id/CF1A2655-FFC9-BD7A-E9A6-F94F1D81FE5C
treatment provided by	Plazi
scientific name	Drymaeus (Drymaeus) rex
status	sp. nov.

Treatment

Drymaeus (Drymaeus) rex spec.nov.

( Figs 7 View FIGURE 7 , 8 View FIGURE 8 I ─S)

Diagnosis. A relatively large species of Drymaeus , with a white line below the suture and typically with three interrupted spiral colour bands on the last whorl, crossing weaker axial streaks of a less intense colour. Aperture with a white, slightly expanded lip, bordered pink inside.

Description. Shell up to 40.7 mm (further dimension given in Table 1 View TABLE 1 ), 2.2 times longer than wide, narrowly rimate with rather convex sides, rather elongated, solid. Colour very variable, whitish-yellowish to yellowish-brown, with the following patterns: a) chestnut-brown axial streaks and three, darker interrupted spiral bands; b) with axial chestnut-brown streaks of varying width, sometimes coalescing; c) axial streaks chestnut-brown and zig-zagging. The spiral bands, if present, are evenly spaced on the last whorl, one at the periphery. Upper whorls in the same ground colour as the rest of the shell or with a pinkish hue; in the latter case the apex is dark reddish-black. Surface somewhat shining, in most cases dull; the upper whorls smooth, on the remaining whorls the growth striae are slightly thickened, most noticeable on the third and fourth whorl. Protoconch with a grating sculpture of axial riblets and spiral striae, which are of equal strength. Whorls 5.2, rather convex; suture slightly impressed and bordered by a whitish to yellowish line below. Aperture elongate-ovate, 1.8 times longer than wide, 0.52 times the total length. Peristome thin, expanded, especially below, whitish with a pink or orange border inside. Columellar margin curved, reflexed, dilated above and receding. Parietal wall with a thin callus, with a pink or orange hue.

Genitalia. Proximal part of the penis with a sheath (ca. 1/5 the length of the phallus), distally slightly swollen and passing without external differentiation into the epihallus. The flagellum is slightly tapering, relatively thick, ca. 1/8 the length of the phallus; the distally attached retractor muscle relatively short and thin. Internally three different zones may be distinguished in the penis: proximal part with longitudinal folds of various lengths, the median part with fewer folds bearing cross-folds, the distal part with a bulgy fold and smaller folds at right angles; epiphallus with longitudinal folds, flagellum with short longitudinal ridges. Spermathecal duct somewhat swollen proximally, subcylindrical in its lower part, thereafter constricted towards the elongate-globose spermatheca. The spermatophore is curved, cylindrical and tapering at both ends.

Pallial organs. Nephridium elongate-truncated, passing into a very short adrenal (primary) ureter, which tapers into the relatively long and wide adrectal (secondary) ureter. Urinary opening at inner side of the pneumostome. Pericardium situated alongside the nephridium, triangularly shaped; ventriculum about twice the size of the aorta. Pulmonary vein ramified towards the mantle edge; a secundary vein runs parallel under the adrectal ureter, with side veins towards the main pulmonary vein, becoming stronger and ramified near the pneumostome.

Type material. Venezuela, Estado Amazonas, Cerro de la Neblina massif, 5.3 km NE Pico Phelps at the base of the escarpment 1 km NE Pico Maguire, Camp VII [00° 50’ 40” N 65° 58’ 10” W], ca. 1800 m, R.W. McDiarmid leg., 31.i ─ 10.ii.1985. Holotype UF 284726, paratypes: Ibidem, UF 284725/1, 284730/1); Ibidem, L. Cocroft leg., 10─ 13.ii.1985 (UF 284736/1); Ibidem, A. Paolillo leg., 10─ 13.ii.1985 (UF 284744/1, 284745/1); Ibidem, 3 km NE Pico Phelps, Camp II [00° 49’ 40” N 65° 59’ 00” W], 2085─ 2100 m, R.W. McDiarmid leg., 28.ii.1985, in Brocchinia plants ( RMNH 112026 /2, UF 284714/2, 284715/1, 284719/2, 284720/1, 284721/1, 284722/2 + 1 juv.); Ibidem, 2 km NNW Pico Phelps, in leaf litter, Camp V [00° 49’ 10” N 66° 00’ 02” W], ca. 1300 m, F.G. Thompson leg., 13.iv.1984 (UF 284759/1); Idem, Idem, 6.25 km NNE Pico Phelps, Camp XI [00° 52’ 00” N 65° 58’ 42” W], 1400─ 1500 m, R.W. McDiarmid leg., ii.1985, in forest (UF 284748/ 1 subadult); Ibidem, 2.0 km SW Neblina Base Camp, 200 m, R.W. McDiarmid leg., 22.ii.1985, in tree 2 m off ground (UF 284747/1).

Remarks. As often seen in Drymaeus , this species shows a great deal of variation in colour and pattern. One specimen (UF 284730) is evenly coloured, the last whorl lighter than the upper whorls, the axial streaks hardly noticeable. This species is also rather variable in shape. Three specimens are somewhat aberrant and have hardly any transition between columellar and parietal margin, giving the aperture a skewed appearance. Of these, one specimen (UF 284759) has the columellar margin straight and the aperture is ear-shaped. In two other specimens (UF 284747, 284748) the aperture is also somewhat ear-shaped, but the columella shows a slight fold. The specimens have been collected at lower elevations (1450, 1300 and 200 m respectively), but it is not clear from the material at hand if there is a correlation between elevation and morphology.

Comparison with other taxa. This species is closely allied to Drymaeus (D.) yapacanensis Breure & Eskens, 1981 , from which it differs in (1) being stouter; (2) having a more swollen last whorl; (3) having less whorls. This new species is also very similar to Drymaeus (D.) steyermarki ( Haas, 1955) from which it differs in (1) being larger; (2) missing the thread-like columellar fold. It may also be compared to D. (D.) extraneus ( Haas, 1955) , from which it differs in (1) having the surface less shining; (2) the less dilated columellar margin; (3) the pink lip; (4) the different colour pattern. Drymaeus (D.) edmuelleri ( Albers, 1854) , of which the type material (ZMB 111.929) has been studied, resembles this new species but differs in (1) being smaller and slenderer; (2) having the last whorl less swollen and somewhat protruded at base; (3) having straight sides.

Etymology. Latin rex , king. Named in honour of Roy W. McDiarmid who collected most of the type material. “Roy” is the Old French word for king, but also the Anglicized spelling of a nickname from Scottish Gaelic ruadh (red, referring to the reddish apex in some specimens). The name also refers to the majestical appearance of this species when collected alive. The epithet is used as a noun in apposition.