Ellenstrongia tarasoc, 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 : 828-831

Ellenstrongia tarasoc n. sp.

( Figs 20 ; 49D ; 53G ; Tables 1 ; 2 )

urn:lsid:zoobank.org:act:15841133-50DD-4A04-BCD2-3C70F3CDA25A

TYPE MATERIAL. — Holotype. Tarava Seamounts • dd (height 4.50 mm, width 2.12 mm, Figs 20 A-C, F-I; 53G); Mont Honu , TARASOC Stn DW3340; 18°23’59”S, 154°9’0”W; 787-792 m; MNHN-IM-2000-39448 .

Paratypes. Tarava Seamounts • 22 dd ( Fig. 20D, E ); same locality data as holotype; MNHN-IM-2000-39449 • 4 dd; same locality data as holotype; 27.IX.2009; coll. MB .

TYPE LOCALITY. — Tarava Seamounts: Mont Honu, TARASOC Stn DW3340; 18°23’59”S, 154°9’0”W; 787- 792 m.

OTHER MATERIAL EXAMINED. — Society Islands • 2 dd; Bora Bora, TARASOC Stn DW3416; 16°34’58”S, 151°43’58”W; 914 m; MNHN • 1 dd; Moorea, TARASOC Stn DW3461; 17°26’59”S, 149°49’1”W; 844-877 m; MNHN.

Tuamotu • 1 dd juv.; SW of Kaukura , TARASOC Stn DW3359; 15°56’59”S, 147°7’58”W; 492-980 m; coll. MB • 1 dd; SW of Kaukura , TARASOC Stn DW3359; 15°56’59”S, 147°7’58”W; 492-980 m; MNHN • 54 dd; between Tikehau and Rangiroa, TARASOC Stn DW 3349; 15°4’58”S, 148°3’0”W; 976-997 m; MNHN • 4 dd; between Tikehau and Rangiroa, TARASOC Stn DW 3351; 15°4’1”S, 148°1’1”W; 976-983 m; MNHN • 1 dd; Tikehau , TARASOC Stn DW 3387; 14°56’59”S, 148°16’1”W; 550-600 m; MNHN-IM-2009-17712 • 1 dd; Tikehau , TARASOC Stn DW 3389; 14°55’1”S, 148°15’0”W; 889 m; MNHN .

Australes • 1 dd juv.; Récif Neilson, BENTHAUS Stn DW1925; 27°0’0”S, 146°4’58”W; 560-790 m; MNHN • 1 dd juv.; Marotiri, BENTHAUS Stn DW1886; 27°51’0”S, 143°31’58”W; 620- 1000 m; 6.XI.2002; MNHN • 5 dd; Banc Président Thiers, BENTHAUS Stn DW1932; 24°40’58”S, 146°1’58”W; 500- 800 m; 14.XI.2002; MNHN • 3 dd; Marotiri, BENTHAUS Stn DW1886; 27°51’0”S, 143°31’58”W; 620-1000 m; 6.XI.2002; MNHN • 4 dd; Marotiri, BENTHAUS Stn DW1885; 27°52’1”S, 143°33’0”W; 700-800 m; 6.XI.2002; MNHN • 5 dd; Marotiri BENTHAUS Stn DW1884; 27°53’59”S, 143°33’0”W; 570- 620 m; MNHN • 1 dd; Banc Arago, BENTHAUS Stn DW1981; 23°21’0”S, 150°43’1”W; 650-1150 m; MNHN • 1 juv.; Banc Arago, BENTHAUS Stn DW1975; 23°23’59”S, 150°43’58”W; 600-691 m; 20.XI.2002; MNHN • 26 dd. (9 juv.); S of Rurutu , BENTHAUS Stn DW2010; 22°31’58”S, 151°20’59”W; 520-950 m; 24.XI.2002; MNHN • 99 dd, 6 lv; E of Rapa , BENTHAUS Stn DW1889; 27°37’1”S, 144°16’1”W; 600- 620 m; 7.XI.2002; MNHN • 1 dd; Tubuai, BENTHAUS Stn DW1955; 23°19’1”S, 149°25’58”W; 750-850 m; MNHN • 1 lv; Tubuai, BENTHAUS Stn DW1962; 23°21’0”S, 149°33’0”W; 470-800 m; 19.XI.2002; MNHN • 3 dd; Rimatara, BENTHAUS Stn DW2020; 22°37’1”S, 152°49’1”W; 920-930 m; 25.XI.2002; MNHN • 8 dd; Rimatara, BENTHAUS Stn DW2021; 22°37’1”S, 152°49’1”W; 1200-1226 m; 25.XI.2002; MNHN • 6 dd; Récif Neilson, BENTHAUS Stn DW1925; 27°0’0”S, 146°4’58”W; 560-790 m; 12.XI.2002; MNHN • 3 dd; E coast of Rurutu , BENTHAUS Stn DW 2004; 22°27’43”S, 151°18’43”W; 430-850 n; 24.XI.2002; MNHN • 1 dd; N of Raivavae , BENTHAUS Stn DW1943; 23°49’1”S, 147°39’0”W; 950 m; 5.XI.2002; MNHN. TARAVA SEAMOUNTS • 1 dd; Mont Ari’i Moana, TARASOC Stn DW3313; 19°13’58”S, 151°37’1”W; 670-770 m; 24.IX.2009; MNHN • 1 dd; Mont Ari’i Moana, TARASOC Stn DW3314; 19°13’58”S, 151°39’0”W; 803-815 m; 24.IX.2009; MNHN • 1 dd; Mont Ari’i Moana, TARASOC Stn DW3317; 19°13’1”S, 151°28’58”W; 593-668 m; 25.IX.2009; MNHN • 1 dd; Mont Ari’i Moana, TARASOC Stn DW3324; 19°15’0”S, 151°34’1”W; 554-630 m; 26.IX.2009; MNHN • 10 dd; Mont ‘Otaha, TARASOC Stn DW3327; 18°45’0”S, 152°16’1”W; 747- 836 m; 26.IX.2009; MNHN • 31 dd; Mont ‘Otaha, TARASOC Stn DW3328; 18°46’1”S, 152°15’0”W; 788-836 m; 26.IX.2009; MNHN • 3 dd; Mont ‘Otaha, TARASOC Stn DW3328; 18°46’1”S, 152°15’0”W; 788-836 m; 26.IX.2009; coll. MB • 7 dd; Mont ‘Otaha, TARASOC Stn CP3329; 18°45’0”S, 152°16’1”W; 755-840 m; 26.IX.2009; MNHN • 2 dd; Mont ‘Otaha, TARASOC Stn DW3330; 18°45’0”S, 152°15’35”W 7; 717-794 m; 26.IX.2009; MNHN • 3 dd; Mont ‘Otaha,TARASOC Stn DW3331; 18°45’0”S, 152°16’58”W; 766 m; 26.IX.2009; MNHN • 4 dd; Mont ‘Otaha, TARASOC Stn DW3332; 18°45’0”S, 152°18’0”W 0; 790-880 m; 26.IX.2009; MNHN • 3 dd; Mont ‘Otaha, TARASOC Stn DW3333; 18°45’0”S, 152°18’0”W; 795-975 m; 26.IX.2009; MNHN • 13 dd; Mont Punu Taipu,TARASOC Stn DW3302; 19°15’0”S, 150°56’59”W; 600-660 m; 23.IX.2009; MNHN.

DISTRIBUTION AND SYMPATRY. — The species is known from the South Pacific Ocean in the Tarava Seamounts (Mont Honu, Mont ‘Otaha, Mont Ari’i Moana, Mont Punu Taipu), Society Islands (Moorea, Bora Bora), Tuamotu (Kaukura, between Tikehau and Rangiroa, Tikehau), Australes (Marotiri, Rapa, Recif Neilson, Banc Président Thiers, Raivavae, Tubuai, Banc Arago, Rurutu, Rimatara), with empty shells collected in 430-1226 m, and 7 live specimens collected in 470-800 m in various stations ( Fig. 49D ).

DIAGNOSIS. — As for the genus Ellenstrongia n. gen.

DESCRIPTION OF HOLOTYPE

Shell ( Figs 20 A-C, F; 53G)

Medium size for the family, height 4.50 mm, width 2.12 mm, height/width ratio 2.12, robust, ovate-conical, slender and pointed.

Protoconch ( Fig. 20E, I )

Species Areas Alvania letourneuxi n. sp. Alvania herosae n. sp. Alvania parvimaculata n. sp. Alvania prosocostata n. sp. Alvania uapou n. sp. Alvania letourneuxi n. sp. Marquesas Tuamotu Gambier Society Australes Alvania herosae n. sp. Marquesas Tuamotu Gambier Society Australes Alvania parvimaculata n. sp.

Slender, acute, multispiral, of 2.75 little convex whorls, height 0.467 mm, nucleus diameter 0.062 mm, first half whorl diameter 0.137, maximum diameter 0.387; protoconch I sculptured by dense microgranules; protoconch I-protoconch II boundary well visible and sinuous; protoconch II with 2 zig-zag spiral cordlets, interspaces with microtubercles and a series of axial rodlets. Protoconch-teleoconch boundary well marked, opisthocline and sinuous, with sinusigera notch ( Fig. 20I ).

Marquesas Tuamotu

Teleoconch

Gambier Society Australes Alvania prosocostata Marquesas n. sp. Tuamotu Gambier Society Australes Alvania uapou n. sp. Marquesas Tuamotu Gambier Society Australes

Of 5.75 very convex whorls with deep sutures. Axial sculpture on the last whorl of 11 ortocline ribs, plus the labial varix, slightly sinuous and rather acute, very narrower than the interspaces, interrupting gradually on the base. Spiral sculpture weak and flattened, subtler than interspaces ( Fig. 20G ), 18 cordlets on the last whorl, of which 11 above the aperture and 7 on the base. The 2-3 subsutural spiral cordlets are weaker. Microsculpture of growth striae and minute pits randomly distributed, over the entire surface ( Fig. 20H ). Umbilical fissure absent. Aperture piriform, height 1.47 mm, height/height aperture ratio 3.06, peristome continuos, wide and rather thick outer varix; sharp lip, internally smooth, ortocline.

Colour

Teleoconch uniform white; protoconch light orange.

Operculum and soft parts

Not examined.

VARIABILITY

We examined 247 specimens, some of which are immature. Size ranges for adult specimens from 3.82 to 4.50 mm. Ellenstrongia tarasoc n. gen., n. sp., despite having a wide distribution in French Polynesia, shows a negligible morphological variation (see Table 1 and Appendix 7).

REMARKS

Ellenstrongia tarasoc n. gen., n. sp. is not directly comparable to almost any known rissoid species, due to the unique combination of shell outline, peculiar microsculpture of the teleoconch and sculpture of the coloured protoconch. Porosalvania profundior Gofas, 2007 , from the Hyères Seamount, 31°09.5’N, 28°43.5’W, 845 m ( Gofas 2007: 861, figs 53, 54 ), is similar in its slender shell and pitted microsculpture on the teleoconch. It differs in the smaller size (<3.5 mm height vs> 3.8 mm height in E. tarasoc n. gen., n. sp.); fewer whorls with less incised sutures; larger but narrower aperture; sparser spiral sculpture; teleoconch microsculpture of minute pits more orderly arranged in spiral series vs randomly distributed, over the entire surface in E. tarasoc n. gen., n. sp.; smooth paucispiral protoconch vs multispiral and markedly sculptured in E. tarasoc n. gen., n. sp. We also found some similarity with the fossil Alvania merlei Van Dingenen, Ceulemans & Landau, 2016 , described from the Zanclean (lower Pliocene) of NW France ( Van Dingenen et al. 2016: 137, pl. 8, figs 4, 5; pl. 9, fig. 3) in the slender outline, the very convex whorls with incised suture, the strong axial sculpture; Alvania merlei differs in the aperture (more acute posteriorly), the more numerous and opisthocline axial ribs (orthocline in E. tarasoc n. gen., n. sp.), and the paucispiral protoconch (multispiral in E. tarasoc n. gen., n. sp.).

Figures

FIG. 20. — Ellenstrongia tarasoc n. gen., n. sp.: A-C, F-I, holotype, height 4.50 mm, width 2.12 mm, Tarava Seamount, Mont Honu, 787-792 m depth stn TARA- SOC DW3340, shell (A-C, F), detail of the protoconch microsculpture (E) (MNHN-IM-2000-39448); D, E, paratype, same data and locality of the holotype, height 4.22 mm width 1.97 mm (coll. MB), shell (D), detail of the first whorls (E), (SEM) shell (F), details of the teleoconch microsculpture (G, H), detail of the protoconch microsculpture (I). Scale bars: E, 20 μm, G-I, 100 μm.

FIG. 49. — Type locality of Alvania isolata (Laseron, 1956) (○, Christmas Island), and location of the stations of the “Valdivia” deep-water expedition (●) where types of Alvania denseclathrata (Thiele, 1925) (Stns 81, 95 and 104) and of Alvania proditoris (Thiele, 1925) n. comb. (Stns 81, 95 and 101) were collected.

FIG. 53. — Alvania Risso,1826,Ellenstrongia n. gen., Haurakia Iredale,1915,Parashiela Laseron,1956,Simulamerelina Ponder,1985 and Substea Cotton,1944:A, Alvania letouneuxi n.sp., holotype,MNHN-IM-2000 38703, height 1.60 mm; B, Alvania herosae n. sp., holotype,MNHN-IM-2000-38704, height 2.02 mm;C, Alvania herosae n.sp.(morph B),MNHN,height 2.16 mm;D, Alvania parvimaculata n. sp.,holotype,MNHN-IM-2000-38706, height 1.65 mm;E, Alvania prosocostata n.sp., holotype, MNHN-IM-2000-38708 height 2.05 mm; F, Alvania uapou n. sp., holotype, MNHN-IM-2000-38710, height 1.70 mm; G, Ellenstrongia tarasoc n. gen., n. sp., holotype,MNHN-IM-2000-39448, height 4.50 mm; H, Haurakia marmorata (Hedley, 1907), Society Islands,height 1.95 mm, coll. JL; I, Parashiela ambulata Laseron, 1956, Australes: Rapa Pointe Kauira, height 1.60 mm, MNHN; J, Parashiela expansilabrum n. sp. holotype, MNHN-IM-2000-38712 height 1.47 mm; K, Parashiela obesula n. sp. holotype, MNHN-IM-2000-38714, height 1.32 mm; L, Parashiela rimatara n. sp. holotype, MNHN-IM-2000-38716, height 1.47 mm; M, Parashiela rotundata n. sp. holotype, MNHN-IM-200038718-, height 1.10 mm; N, Parashiela soniae n. sp., holotype, MNHN-IM-2000-38720, height 1.17 mm; O, Simulamerelina australes n. sp. holotype, MNHN-IM-2000-38722, height 2.47 mm; P, Simulamerelina densestriata n. sp., holotype, MNHN-IM-2000-38724, height 2.45 mm; Q, Simulamerelina gracilis n. sp., holotype, MNHN-IM-2000-38726, height 2.45 mm; R, Simulamerelina lepteseiras n. sp., holotype, MNHN- IM-2000-38727, height 1.47 mm; S, Simulamerelina micrometrica n. sp., holotype, MNHN-IM-2000-38728, height 1.33 mm; T, Simulamerelina tuamotu n. sp. holotype, MNHN-IM-2000-38730, height 1.57 mm; U, Subestea moruroa n. sp., holotype, MNHN-IM-2000-38732, height 1.96 mm.

FIG. 54. — Tree-portraying similarity among the studied areas,after an UPGMA cluster analysis on a similarity matrix (Jaccard index) based on presence/absence of the studied species in each archipelago and the Tarava Seamounts.