Teretia sysoevi, Morassi, Mauro & Bonfitto, Antonio, 2015

Morassi, Mauro & Bonfitto, Antonio, 2015, New Indo-Pacific species of the genus Teretia Norman, 1888 (Gastropoda: Raphitomidae), Zootaxa 3911 (4), pp. 560-570 : 562-564

Teretia sysoevi sp. nov.

Figures 1 .L–T

Type material. Holotype ( MNHN IM- 2000-28375) and two paratypes (paratype 1 MNHN IM- 2000-28377 (coated); paratype 2 MZB 60096).

Type locality. Wallis & Futuna Islands, 14°19,6'S 178°06,7'E, 419–425 m [MUSORSTOM 7 stn DW 507], 11 May 1992.

Material examined. Wallis & Futuna Islands, 14°19,6'S 178°06,7'E, 419–425 m [MUSORSTOM 7 stn DW 507], 11 May 1992 (1 dd, holotype); New Caledonia: 18°48,20’S 163°10,80’E, 720 m [MUSORSTOM 4 stn DC 168] 16 September 1985 (1 dd, paratype 1); Loyalty Ridge: 23° 54.46 S 169° 49.15 E, 699–715 m [N/ O “Alis” BATHUS 3 stn DW 786], Bouchet, Richer & Warén coll. 25 November 1993 (1 dd, paratype 2).

Description. Shell ( Figs. 1 .L– O) fusiform (b/l 0.39; a/l 0.38) with high spire, strongly excavated base and relatively short anterior canal. Teleoconch of five whorls (six in paratypes) with shallowly impressed, linear suture. Subsutural ramp wide, moderately deeply concave. Earlier two teleoconch whorls with a prominent peripheral cord below mid- height of the whorl and two weak cords bordering abapical part of subsutural ramp (the abapical one bisected). On third whorl a second main spiral cord develops at level of abapical suture increasing in strength on subsequent whorls ( Fig. 1 .P). In one paratype the second main cord develops from first whorl onwards. Last whorl with a third main spiral cord near abapical suture and one weak cord in the interspace between peripheral and second main cords. Last whorl with 19 spiral cords on base and rostrum. Subsutural ramp lacking spiral sculpture (holotype) or with up to four low threads (paratypes) on later two whorls. Teleoconch whorls sculptured by fine axial growth lines forming weak, irregularly spaced, arcuate plicules on subsutural ramp ( Fig. 1 .P). Under SEM ( Fig. 1 .R), surface is seen to be covered by a sculpture of dense microscopic pustules. Aperture lanceolate, outer lip thin. Anal sinus very deep, narrow, asymmetrical; its deepest point on sutural ramp. Protoconch ( Figs. 1 .S–T) of 2½+ whorls; tip missing, remaining whorls with diagonally cancellate sculpture terminating a short distance above abapical suture where fine slightly prosocline riblets occur. Maximum diameter about 0.48 mm. Colour of teleoconch whitish to pale buff, protoconch light brown. Dimensions: Holotype 5.8 x 2.3 mm, aperture height 2.2 mm. Largest Paratype (MZB): 7.5 x 2.9 mm, aperture height 3.1 mm.

Remarks. Teretia sysoevi sp. nov. is morphologically similar to Teretia neocaledonica sp. nov. from which it differs in numerous details of shell morphology. Teretia sysoevi sp. nov. has more numerous teleoconch whorls (5–6 versus 4–4¾), a more deeply concave subsutural ramp lacking spiral cords near adapical suture and the growth lines consist of very fine lines rather than axial plicules (compare Figs. 1.E–F with Fig. 1 .P–Q). Under SEM, T. sysoevi has a distinctive sculpture of dense microscopic pustules ( Fig. 1 .R) while T. neocaledonica has sparser granules ( Fig. 1.G ). The two species further differ in colour: T. sysoevi has a whitish to pale buff shell lacking the brown band typically occurring on periphery of spire whorls of T. neocaledonica .

Etymology. Named after Alexander Sysoev of Zoological Museum, Moscow State University ( Russia) in recognition to his contribution to our knowledge of the turriform gastropods.

Figures

FIGURE 1. A – J. Teretia neocaledonica sp. nov. A. Holotype (MNHN IM- 2000 - 28374), New Caledonia, Cruise SMIB 8, stn DW 146 - 147, 5.9 x 2.4 mm. B – J. Paratype (MZB 60095), New Caledonia, Cruise SMIB 8, stn DW 146 - 147. B. Shell, 4.9 x 2.1 mm. C – D. Coated specimen, frontal and lateral view, scale bar 2 mm. E. Penultimate whorl, scale bar 500 µm. F – G. Microsculpture of penultimate whorl, scale bar 100 µm. H – I. Protoconch, scale bar 500 µm. J. Details of protoconch 1, scale bar 100 µm. L – T. Teretia sysoevi sp. nov. L – M. Holotype (MNHN IM- 2000 - 28375), South-West Pacific, Cruise MUSORSTOM 7, stn DW 507, 5.8 x 2.3 mm. N. Paratype 1 (MNHN IM- 2000 - 28377), New Caledonia, Cruise BATHUS 3, stn DW 786, 7.2 x 2.8 mm. O – T. Paratype 2 (MZB 60096), New Caledonia, Cruise MUSORSTOM 4, stn DC 168. O. Shell, 7.5 x 2.9 mm scale bar 1 mm. P. Penultimate whorl, scale bar 600 µm. Q. Microsculpture of penultimate whorl, scale bar 200 µm. R. Microsculpture of penultimate whorl, scale bar 80 µm. S – T. Protoconch, scale bar 200 µm.