Adelopoma gracile Greķe, 2023

Greķe, Kristīne, Kagainis, Uģis & Telnov, Dmitry, 2023, First record of the family Diplommatinidae Gray, 1847 (Gastropoda: Architaenioglossa) from Ecuador with description of a new Adelopoma Doering, 1885, Zootaxa 5339 (3), pp. 273-284 : 275-279

Adelopoma gracile Greķe , sp. nov.

( Figs 1–4 , 5 )

urn:lsid:zoobank.org:act:21F1E561-A395-492D-AAC0-AEF124C17596

Type material designated. Holotype LOUNAZ: ECUADOR central, Prov. Tungurahua, E Andes, ~ 1–2 km NE Rio Negro , 1°23’59”S 78°10’49”W, “Ecominga” private reserve, 8.ii.2023, 1315–1325 m, primary mid-montane rainforest, leg. D.Telnov [ LOUNAZ I 0017180 ] . Paratypes 74 specimens (of them 5 juvenile shells). 7 NHMUK [ NHMUK 20230565 ], 6 LNDM [ LDM Z 5 /6401–LDM Z 5/6406] , 19 specimens LOUNAZ [ LOUNAZ I 0017181– 0017199 ], 6 KGC: same locality as holotype; 7 NHMUK [ NHMUK 20230566 ], 6 LNDM [ LDM Z 5 /6407–LDM Z 5/6412] , 18 specimens LOUNAZ [ LOUNAZ I 0017200–0017217 ], 5 KGC: ECUADOR central, Prov. Tungurahua, E Andes, ~ 2.5 km SSW Rio Verde, valley of River Pastaza, 1°24’34”S 78°16’37”W, “Ecominga” private reserve, 9.ii.2023, 1350–1500 m, primary mid-montane rainforest on dolomite, leg. D.Telnov. Additional material. One fragmented shell (same locality as holotype) ( Fig. 2 ) which is not designated as a paratype due to the condition of the shell, which is strongly fragmented.

Derivatio nominis. Named from Latin ‘gracilis’ (slender, slim) to highlight the slender shell of this new species. Gender feminine.

Description. Holotype ( Fig. 1 ), shell height = 2.3 mm, width = 1.3 mm, height of the ultimate whorl = 1.2 mm, aperture diameter = 0.7 mm. Selected paratypes (n=3) from the type locality, height 2.3; 2.4; 2.3 mm, width 1.4; 1.2; 1.2 mm, height of ultimate whorl 1.2; 1.1; 1.1 mm, aperture diameter 0.65; 0.6; 0.6 mm; selected paratypes (n=3) from ~ 2.5 km SSW Rio Verde, height 2.1; 2.35; 2.3 mm, width 1.1; 1.2; 1.2 mm, height of ultimate whorl 1; 1;25; 1.3 mm, aperture diameter 0.6; 0.65; 0.65 mm.

Shell sinistral, turriform, maximum width more than half shell height. Shell white, subtranslucent, when alive appears in part yellow and in part brownish due to colouration of body. Number of whorls about 6. Protoconch bluntly rounded, of 1.5 whorls, inconspicuously axially microscopically wrinkled ( Fig. 4A ). Teleoconch whorls subopaque, three last whorls inflated, whorl profile rounded, whorls moderately inclined with regards to coiling axis. Whorls evenly widen except for ultimate whorl; ultimate and penultimate whorl about same width in apertural view. Penultimate whorl appears comparatively stronger bulbous than any other (e.g., in top and bottom view). Constriction not or very poorly defined on wall of penultimate whorl above aperture.Axial ribs lamellate, moderately high and dense, slightly arched or sinuous, extending from suture to suture, at suture not synchronous with ribs on adjacent. Axial ribs evenly distributed, denser on early first teleoconch whorl, no abrupt changes in ribbing pattern on last three teleoconch whorls. Ten to twelve axial ribs on ultimate whorl in apertural view. There are 7.4–8.6 ± 0.85 ribs per 1 mm on penultimate whorl in apertural view; 16–18 ribs on ultimate whorl. Interspaces between axial ribs equivalent to 5.53 ± 0.7 to 7.655 ± 1.9 times ribs width, mean distance between axial ribs on ultimate whorl in apertural view 0.12‒0.13 mm. Microscopic spiral raised striae of teleoconch very delicate, dense, present between and on axial ribs. There are 16‒18 rows of spiral ribs per 0.1 mm on ultimate whorl in apertural view. Suture deep. Umbilicus very narrow in adult. Aperture circular, somewhat shifted left with regard to coiling axis in apertural view (not centrally positioned), not projecting anteriad, nearly parallel to coiling axis in lateral profile. Peristome double. Inner peristome slightly attached to wall of ultimate whorl, somewhat deflected outwards, not modified into broad, flattened ‘lip’. Inner peristome continuous, transition of shell channel to ‘lip’ is even, not angulate. Outer peristome comparatively stronger developed than inner, discontinuous at parietal margin of aperture. A series of 7–11 thin calcareous layers (growth lines) between inner and outer peristome (in lateral profile). Inner peristome nearly straight, outer peristome slightly sinuous (in lateral profile). Columella ( Fig. 2 ) with moderately strong basal lamella in ultimate whorl; lamella ends in an inconspicuous denticle on columellar margin of aperture ( Fig. 4E ). Operculum primitive, circular, thin, translucent, yellowish, paucispiral, with central nucleus, enclosing entire aperture.

Sexual dimorphism. Inconspicuous. The largest female shells are comparatively 0.05‒0.1 mm longer and same wider (slightly stronger obese) than those of males, but the majority of male and female shells are of same dimensions.

Differential diagnosis. The new species appears conchologically most close to A. paraguayana Parodíz, 1944 from Argentina and Paraguay and A. peruvianum Hausdorf & Muñoz, 2004 from northern Peru but is specifically different in the strongly double peristome, the considerable less strong expansion (deflection) of the ‘lip’ of the inner peristome compared to that of both congeners, differently dense spiral ribbing pattern (about 16‒18 spiral ribs per 0.1 mm on the ultimate whorl in the apertural view in A. gracile Greķe , sp. nov. versus about 21–22 ribs in A. paraguayana and about 11‒15 ribs in A. peruvianum ) and axial ribbing pattern (mean distance between axial ribs on the ultimate whorl in apertural view 0.12‒0.13 mm in A. gracile Greķe , sp. nov. versus about 0.11 mm in A. paraguayana and about 0.15‒0.16 mm in A. peruvianum ), the significantly stronger spiral ribbing pattern compared to that in A. paraguayana . The axial ribs are distinctly lower in A. gracile Greķe , sp. nov. compared to those in A. paulistanum Martins & Simone, 2014 (Atlantic coast of Brazil), the spiral ribbing pattern is less dense and the denticle at the columellar margin of the aperture is comparatively stronger in the new species. The peristome nearly parallel to the coiling axis in lateral profile in A. gracile Greķe , sp. nov., distinctly prosocline in both A. paraguayana and A. peruvianum . The transition of the shell channel to the ‘lip’ of the inner peristome is even in A. gracile Greķe , sp. nov., somewhat obtusely angulate in both A. paraguayana and A. peruvianum . Adelopoma paulistanum , which is unlikely to occur in the Ecuadorian Andes, shares the non-angulate transition of the shell channel to the ‘lip’ of the inner peristome with the new species, but the shell is somewhat larger of about 2.6–2.9 mm height (about 2.1–2.4 mm in A. gracile Greķe , sp. nov.), the axial ribs are comparatively stronger sinuous, the shell shape is generally less slender, the axial ribbing pattern is denser around the constriction area than on the rest of the pen- and ultimate whorl (the axial ribbing pattern is not becoming denser around the construction area above the aperture in A. gracile Greķe , sp. nov.), and the columellar denticle is even less prominent than that in A. gracile Greķe , sp. nov..

Ecology. Occurs in wet leaf litter on primary mid-montane rainforest floor, about 1300‒1500 m. Most specimens observed at base of limestone and dolomite rocks where dense layer of moist leaf litter accumulates.

Distribution. River Pastaza valley, Tungurahua Province, Central Ecuador.

Figures

FIGURE 1. Adelopoma gracile Greķe, sp. nov. holotype shell (LOUNAZ I 0017180). A. Apertural view. B. Abapertural view. C. Lateral view. D. Apical view. E. Umbilical view [scale bar: 1 mm].

FIGURE 2. Adelopoma gracile Greķe, sp. nov. additional specimen (not type) from ~1–2 km NE Rio Negro, columella. The arrow indicates basal columellar lamella.

FIGURE 3. Adelopoma gracile Greķe, sp. nov. paratype shells, micrographs. A. Specimen (LDM Z 5/6401) from ~1–2 km NE Rio Negro, apertural view. B–C. Specimen (LDM Z 5/6407) from ~2.5 km SSW Rio Verde, apertural (B) and lateral (C) view.

FIGURE 4. Adelopoma gracile Greķe, sp. nov. paratype (LDM Z 5/6407) from ~2.5 km SSW Rio Verde, micrographs. A. Protoconch, apertural view. B. Sculpture of ultimate whorl above aperture, apertural view. C. Sculpture on penultimate whorl, lateral view. D. Sculpture of ultimate whorl above aperture, apertural view. E. Peristome, lateral view. F. Columellaris.

FIGURE 5. Relief map of Ecuador with the localities (black dots) of Adelopoma gracile Greķe, sp. nov. (prepared with Arc View 9.0) [scale 1:3 000 000].