Flexopteron akainakares, Roland & Virginie, 2015

Roland, Houart & Virginie, Héros, 2015, New species of Muricidae Rafinesque, 1815 (Mollusca: Gastropoda) from the Western Indian Ocean, Zoosystema 37 (3), pp. 481-503 : 494-497

Flexopteron akainakares n. sp.

( Figs 2D, E ; 6P, Q ; 8 A-E; 9B; 14B, C)

TYPE MATERIAL. — Holotype (dd) MNHN-IM-2000-30012 and 4 paratypes MNHN, 1 paratype coll. RH (as listed below).

FIG. 11. — Distributions of: A, Murexsul mananteninaensis n. sp.; B, Typhinellus laminatus n. sp. Symbols: ★, type locality; ■, other occurences.

TYPE LOCALITY. — South Madagascar, Manantenina sector, 24°23’S, 47°32’E, 307-319 m [ATIMO VATAE: stn DW3524].

MATERIAL EXAMINED. — South Madagascar. ATIMO VATAE: stn DW3515, between Lokaro and Sainte Luce, 24°53’S, 47°28’E, 184-203 m, 1 lv, 2 dd (paratypes MNHN-IM-2000-30013). — Stn DW3524, Manantenina sector, 24°23’S, 47°32’E, 307-319 m, 1 dd (holotype MNHN-IM-2000-30012), 3 dd, juv. — Stn DW3528, Manantenina sector, 24°24’S, 47°33’E, 424-438 m, 13 dd (1 paratype Coll. RH). — Stn DW3529, Manantenina sector, 24°24’S, 47°33’E, 402-407 m, 1 dd (paratype MNHN-IM-2000-30014). — Stn DW3534, Sainte Luce sector, 24°43’S, 47°32’E, 296-307 m, 2 dd, juv.

DISTRIBUTION. — South Madagascar, taken alive at 184-203 m, shells at 203- 424 m.

ETYMOLOGY. — Greek, akaina, spine and akares, short, small. This species is named for the small and short spines on the axial lamellae.

DESCRIPTION

Shell medium sized for the subgenus, up to 12.2 mm in height at maturity. Height/width ratio 1.5-1.7. Broadly ovate, weakly spinose, lightly built. Subsutural ramp narrow, weakly sloping on spire whorls, broader, strongly sloping on last teleoconch whorl, weakly concave. Shell entirely white.

Spire high with 1.5 protoconch whorls and up to 4.15 broad, convex, angular, strongly shouldered, weakly spinose whorls. Suture impressed. Protoconch large, broad, whorls rounded, smooth, maximum width 900-1000 µm.Terminal lip weakly raised, narrow, prosocline.

Axial sculpture of teleoconch whorls consisting of low, narrow, weakly webbed lamellae, more strongly developed at shoulder, producing short, narrow, broadly open spines at intersection of lamellae and primary spiral cords. First whorl with 6 or 7 lamellae, second with 7 or 8, third 7-9, fourth 6-9, last (apertural) with 6-7. Spiral sculpture of high, rounded, narrow, weakly squamous, primary cords, low, narrow secondary cords and numerous, narrow, low threads. First teleoconch whorl with P1 and P2, broadly separated by a large gap, second whorl with P1 and P2, starting weak s1 and one or two threads, third whorl with P1 and P2, weak s1 and narrow, weak threads of various strength, fourth and last whorls with P1, s1, P2, P3, P4, (s4), P5, (s5), P6, s6, adp and several threads of different magnitude.

Aperture small, ovate. Columellar lip broad, flaring, smooth or occasionally with one or two weak knobs abapically, rim partially erect, adherent at adapical extremity. Occasionally with weak, very low parietal tooth at adapical extremity. Anal notch shallow, broad. Outer lip weakly erect, smooth with four weak or moderately strong, broad denticles within: D1, D2, D3, D4-D5 fused. Siphonal canal short, broad, weakly dorsally recurved, broadly open.

Operculum ovate, light brown with apical nucleus.

Radula ( Fig. 14B, C ) muricine with broad rachidian bearing long, narrow, central cusp; short, triangular lateral denticles, almost half the size of central cusp; broad, long, triangular lateral cusps. Marginal area short, occasionally with small marginal denticle, almost indistinct when present. Marginal cusp short, outwardly bent.

Lateral teeth sickle shaped, long, with broad base.

REMARKS

Flexopteron akainakares n. sp. differs in many ways from F. poppei and does not need to be compared here.

Flexopteron primanova ( Fig. 8 F-I) was described from northern Madagascar but F. akainakares n. sp. is not sympatric, living more to the South. Flexopteron akainakares n. sp. differs in having a relatively smaller shell, a higher and larger protoconch (900-1000 wide and 900 µm high vs 850- 900 wide and 700-800 µm high) with rounded first whorl vs flat in F. primanova , markedly shorter shoulder spines on the last teleoconch whorl in adult specimens, a shorter siphonal canal, a different morphology of the primary spiral cords of the teleoconch whorls, and a last teleoconch whorl with P1, s1, P2, P3, P4, (s4), P5, (s5) and P6, with a broad gap between P1 and P2 as opposed to P1, P2, (s2), P3, P4, P5, (P6).

The radula of F. primanova ( Fig. 14 D-F) is also different in having a very long, narrow central cusp, narrow lateral denticles approximately half the size of the central cusp, long, narrow, lateral cusps even longer than the central cusp, a smooth marginal area and acute, moderately long, marginal cusps.

The operculum is similar, being ovate with an apical nucleus.

Figures

FIG. 2. — Spiral cords and apertural denticles morphology: A, Bouchetia wareni n. sp. (holotype), 18.1 mm; B, Bouchetia vaubanensis (Houart, 1986) (holotype), 10.5 mm; C, Murexsul mananteninaensis n.sp.(holotype),5.2 mm;D, E, Flexopteron akainakares n.sp.(holotype),12,2 mm.Abbreviations:see Material and methods.

FIG. 6. — A, B, Timbellus vespertilio (Kuroda, 1959), East China Sea, Coll. RH, 28 mm; C-G, Timbellus goniodes n. sp., C, D, ATIMO VATAE, stn CP3615, 284- 286 m, holotype MNHN IM-2000-30006, 23.7 mm; E, F, ATIMO VATAE, stn DW3552, 264-280 m, paratype MNHN IM-2000-30007, 14.8 mm; G, protoconch; H, Timbellus crauroptera (Houart, 1991); New Caledonia, BIOCAL, stn DW64, 250 m, holotype MNHN IM-2000-0132, 11.4 mm; I-M, Bouchetia wareni n. sp., Madagascar,MIRIKY,stn CP3189,346-376 m; I, J, holotype MNHN-2007-36941, 18.1 mm;K, L, MIRIKY,stn CP3183,paratype MNHN IM-2007-36941, 12.8 mm; M, protoconch; N, O, Bouchetia vaubanensis Houart,1986;South of New Caledonia,VAUBAN 1976-1978, stn DR01,480-500 m, holotype MNHN IM-2000-0885, 10.5 mm; P, Q, Flexopteron akainakares n. sp., ATIMO VATAE, stn DW3524, 307-319 m, holotype MNHN IM-2000-30012, 12.2 mm. Scale bars: G, M, 500 µm.

FIG. 8. — A-E, Flexopteron akainakares n. sp.: A, B, ATIMO VATAE, stn DW3515, 184-203 m, paratype MNHN IM-2000-30013, 10.2 mm (radula illustrated Fig. 14 B, C); C, D, ATIMO VATAE, stn DW3524, 307-319 m, 6.2 mm; E, protoconch; F-I, Flexopteron primanova (Houart, 1985): F, G, MIRIKY, stn CP3289, 332-379 m, 20.7 mm; H, MIRIKY, stn CP3192, 578-580 m, 16.9 mm; I, protoconch; J-N, Murexsul mananteninaensis n. sp.: J, K, ATIMO VATAE, stn DW3524, 307-319 m, holotype MNHN IM-2000-30015, 5.2 mm; L, M, ATIMO VATAE, stn DW3523, 200-220 m, paratype MNHN IM-2000-30016, 4.5 mm; N, protoconch; O, P, Murexsul queenslandicus Houart, 2004, Australia, Queensland, Southeast of Swain Reefs, 22°26.27’-22°20.2’, 153°17.13’-152°17.6’E, 187 m, paratype RH, 4.5 mm; Q, R, Murexsul charcoti (Houart, 1991), New Caledonia,BIOCAL, stn DW44, 440-450 m, holotype MNHN IM-2000-0067, 7.2 mm; S, Murexsul micra (Houart, 2001), New Caledonia, LAGON, stn 1374, 20-35 m, holotype MNHN IM-2000-0356, 3.7 mm. Scale bars: E, I, N, 500 µm.

FIG.14. — Radulae: A, Vokesimurex rectaspira n. sp.; ATIMO VATAE, stn CP3589, paratype MNHN IM-2000-30001; B, C, Flexopteron akainakares n. sp.; ATIMO VATAE, stn DW3515, paratype MNHN IM-2000-30013; D-F, Flexopteron primanova (Houart, 1985); MIRIKY, stn CP3210, scale bar 25 µm; G, Bouchetia vauban- ensis (Houart, 1986); New Caledonia, BIOCAL, stn DW44. Scale bars: A, 100 µm; B, C, 20 µm, D-F, 25 µm; G, 10 µm.