Alvania denseclathrata ( Thiele, 1925 ) Amati & Giulio & Oliverio, 2023

Amati, Bruno, Giulio, Andrea Di & Oliverio, Marco, 2023, Shallow-water Rissoidae of the genera Alvania Risso 1826 Haurakia Iredale 1915 Parashiela Laseron 1956 Simulamerelina Ponder 1985 and Subestea Cotton 1944 Gastropoda Caenogastropoda Rissooidea from French Polynesia with the description of a new deep-water genus, Zoosystema 45 (25), pp. 803-892 : 806-807

Alvania denseclathrata ( Thiele, 1925) n. comb.

( Figs 2 ; 48 )

Rissoa denseclathrata Thiele, 1925: 81 , pl. 6, fig. 11.

TYPE MATERIAL. — Lectotype. South Africa • dd; Valdivia Stn 95 ; 34°51’0”S, 19°37’47”E; 80 m; ZMB/Ma.64984 (here designated). Paralectotypes. South Africa • 4 dd; Valdivia Stn 95 ; 34°51’0”S, 19°37’47”E; 80 m; ZMB/Ma.64984 • 3 dd; Valdivia Stn 104 ; 35°15’57”S, 22°26’42”E; 155 m; ZMB/Ma.64984 .

Angola • 2 dd; Valdivia Stn 81 ; 16°26’27”S, 11°41’27”E; ZMB/ Ma.64984 .

TYPE LOCALITY. — South Africa, Valdivia Stn 95; 34°51’0”S, 19°37’47”E; 80 m.

DISTRIBUTION. — Only known from southern Africa (Valdivia Stns 95 and 104) and from a station in southern Angola (Valdivia Stn 81) ( Fig. 48 ).

DIAGNOSIS. — Alvania with small (height c. 2 mm), robust shell, ovate-conical; convex whorls with weakly impressed suture; axial and spiral double sculpture dense, of equal thickness; aperture piriform, peristome continuous and simple, outer lip with robust varix; umbilical fissure absent. Protoconch paucispiral, dome-shaped, with spiral sculpture. Colouration uniform whitish.

REMARKS

The lot from southern Angola (Valdivia Stn 81) comes form a completely distinct biogeographic area, and we are not sure it is not a case of mislabelling. In any case, to stabilize the type locality we have designated as lectotype a specimen from the Cape area (Valdivia St. 95). Rissoa denseclathrata is currently included ( Ponder 1985) in Haurakia Iredale, 1915 . However, this is clearly a member of Alvania , with its shell devoid of umbilical fissure, with double sculpture (axial and spiral), piriform aperture, continuous and simple peristome, outer lip with robust varix, dome-shaped paucispiral protoconch with spiral sculpture. Alvania valeriae Absãlao, 1993 from off southeastern Espirito Santo State (southeastern Brazil) 38 m depth ( Absãlao 1993: 104, 105, figs 1-3; Oliveira et al. 2018: 95, fig. 4 I-K), differs from Alvania denseclathrata n. comb. in its protoconch (quite evidently paucispiral and not multispiral as originally described) without sculpture vs sculptured with spiral cordlets in A. denseclathrata n. comb.; in the narrow umbilical fissure, absent in A. denseclathrata n. comb.; in the absence of a labial varix vs a robust labial varix in A. denseclathrata n. comb.

Alvania flexilis Gofas, 1999 from off Ilha de Luanda ( Angola) 40-60 m (Gofas, 1999: 85, figs 27-32), differs from A. denseclathrata ( Thiele, 1925) n. comb., in its multispiral protoconch sculptured with granules vs paucispiral with spiral sculpture in A. denseclathrata n. comb.; in the axial and spiral sulpture on the teleoconch more spaced than in A. denseclathrata n. comb.

We accordingly propose Alvania denseclathrata ( Thiele, 1925) n. comb. as a new combination for Rissoa denseclathrata Thiele, 1925 .

Figures

FIG. 2. — Alvania denseclathrata (Thiele,1925) n. comb.:A-E, Lectotype,height 2.2 mm,width 1.35 mm,South Africa,Valdivia Stn 95, 80 m, ZMB/Moll.N ° 64984: shell (A-C); detail of the first whorls (D, E); F, original labels; G, original drawing. Scale bars: D, E, 20 μm.

FIG. 48. — Distribution maps of the Polynesian species of Alvania Risso, 1826 and Ellenstrongia n. gen.: A, Alvania letourneuxi n. sp. (●) and Alvania herosae n. sp. (○); B, Alvania parvimaculata n. sp. (○) and Alvania prosocostata n. sp. (●); C, Alvania uapou n. sp.; D, Ellenstrongia tarasoc n. gen., n. sp.