Argeneuthria varicosa, Pastorino, Guido, 2016

Pastorino, Guido, 2016, Revision of the genera Pareuthria Strebel, 1905, Glypteuthria Strebel, 1905 and Meteuthria Thiele, 1912 (Gastropoda: Buccinulidae) with the description of three new genera and two new species from Southwestern Atlantic waters, Zootaxa 4179 (3), pp. 301-344 : 335

Argeneuthria varicosa new species

Figures 25 A–M, 26A–F

Type material. Holotype (MACN-In 40537) from Station 10, 18 paratypes: 2 from Station 3, (MACN 40540); 1 from Station 5, (MACN-In 40537); 9 from Station 10, (MACN 40542); 1 from Station 12, (MACN 40539); 2 from Station 43, (MLP 14212); 1 from Station 44, (MACN 40538); all of Talud Continental expedition of RV PUERTO DESEADO

Type locality. Sta. 10, Talud Continental Expedition, RV PUERTO DESEADO, 37º59.706´S, 54º41.854´W, 852 m depth, collected on 08-Oct-2012 with bottom trawl.

Etymology. From the varices that characterize the axial sculpture of the shell.

Description. Shell medium size, about 15.5 mm in height, fusiform, translucent, whitish, of 7 slightly convex, whorls; protoconch ( Figs 25 K, L) conical, whitish, smooth, of 3 flat whorls, the first one smaller, transition to teleoconch well defined; suture impressed; aperture subcircular; siphonal canal wide and short; parietal callus very thin; spiral ornamentation ( Fig. 26 E) of 7 to 8 flat, rectangular cords on the first whorl, 6 to 7 on the second, and about 20 on the last; axial sculpture of irregular varices, around 10 to 15 on the first whorls and then up to 20, obsolete or absent on the last whorl; shell with yellowish deciduous periostracum ( Fig. 26 F).

Operculum ( Fig. 25 M) thin, suboval, nucleus subterminal, close to the external margin; attachment area large, with a wide rim.

Radula ( Fig. 26 A–C) typical of Argeneuthria , however, the central rachidian cusp appears to be slightly larger than the lateral cusps. The external cusp of lateral teeth is also bifid.

Penis ( Fig. 26 D) long, cylindrical with a large, pointy papilla rising from a cavity.

Material examined. Holotype Sta. 10, 37º59.706´S, 54º41.854´W, 852 m depth, collected on 08-Oct-2012 with bottom trawl; and paratypes – Sta. 3, 37º59.657´S, 55º13.050´W, 250 m depth, collected on 08-Oct-2012 with bottom trawl; Sta. 5, 37º58.651´S, 55º9.104´W, 528 m depth, collected on 08-Oct-2012 with bottom trawl; Sta. 12, 37º57.907´S, 54º31.921´W, 1144 m depth, collected on 08-Oct-2012 with dredge; Sta. 43, 37º53.837'S, 54º30.458'W, 998 m depth, collected on 26-May-2013 with bottom trawl; Sta. 44, 37º53.557'S, 54º42.941'W, 780 m depth, collected on 26-May-2013 with bottom trawl; all of Talud Continental Expedition, RV PUERTO DESEADO; 54°59’S, 64°53’W, 586–641 m depth, RV ELTANIN Sta. 970, collected on 11-Feb-1964, (USNM 870516); 3 spms., 54°51.24'S, 63°37.67'W, Burdwood bank, 585 m depth, collected on November-13-2014 with dredge, (MACN 40543).

Distribution. Known from off Mar del Plata, Buenos Aires province (250 to 1144 m depth) to Staten Is. and Burdwood bank.

Remarks. This new species is similar to the Magellanic A. philippi . However, the shell is more slender with a longer spire, larger siphonal canal and the spiral ornamentation is always well defined on the teleoconch. In addition, the protoconch of A. varicosa n. sp. is larger, more conical and with a smaller first whorl. The number and morphology of the spiral cords as well as of the protoconch and varices clearly distinguish the shell of A. varicosa from P. venustula , although they do show certain degree of similarity.

Figures

FIGURE 25. Argeneuthria varicosa sp. nov. A – C. Holotype MACN-In 40537. D – F. Paratype, MACN-In 40540. G – I. Paratype, MACN-In 40542, Scale bar = 1 cm. J. Paratype, MACN-In 40540, SEM detail of the spiral ornamentation, scale bar = 1 mm. K – L. Protoconch of the specimen in figure J, scale bar = 1 mm. M. External and internal view of the operculum, scale bar = 1 mm.

FIGURE 26. Argeneuthria varicosa sp. nov. A – C. Radula, A: dorsal view, scale bar = 20 µm; B: detail of the lateral tooth, scale bar = 25 µm; C: dorsal view, scale bar = 100 µm. D. Penis, critical point dried, scale bar = 500 µm. E. SEM detail of the spiral ornamentation without periostracum, scale bar = 200 µm. F. SEM detail of the spiral ornamentation with periostracum, scale bar = 200 µm.