Turbonilla megascymna, S, Absalão, Ricardo Silva, Santos, Franklin Noel & Oliveira, Deusinete, 2003

S, Absalão, Ricardo Silva, Santos, Franklin Noel & Oliveira, Deusinete, 2003, Five new species of Turbonilla Risso, 1826 (Gastropoda, Heterobranchia, Pyramidellidae) found off the northeast coast of Brazil º­ 13 º, Zootaxa 235, pp. 1-11 : 3-5

Turbonilla megascymna n. sp. ( Figs. 4­7 )

Description: Shell small, conical to subcylindrical, fragile, white, lustrous. Teleoconch whorls strictly convex. Suture well impressed, oblique, almost straight. Protoconch heterostrophic, planispiral with nucleus partially immersed in teleoconch, diameter 323 m in holotype. Axial ribs stout, moderately low, orthocline, about 16 on body whorl of holotype; interspaces as wide as ribs or narrower, disappearing at periphery of last whorl. Spiral ridges of minute pits present over axial ribs and interspaces on the subsutural region, only visible under very high magnification. Base rounded. Aperture oval­pyriform. Columella arcuate. Outer lip fine. No umbilical fissure.

Dimensions: Holotype with 4.5 teleoconch whorls; height 2.3 mm; width 0.6 mm.

Type material: Holotype IBUFRJ 12703. Paratype UFPE 4440, Paratype MORG 41057. All paratypes from 08º42’S 34º44’W, # 15 REVIZEE, 465 m depth, Rv. “Natureza” coll., off Pernambuco State, northeast coast of Brazil, 25/iii/2000.

Type locality: 06º57’32”S 34º29’22”W, #7 REVIZEE, 750 m depth, Rv. “Natureza” coll., off Paraíba State, northeast coast of Brazil, 29/xi/2001.

Distribution: Restricted to the Northeast Brazilian coast from between Pernambuco (08o S) and Paraíba States (6o S).

Etymology: From megascymna is composed by two parts: mega ­ (L) for large, and scymna (L.) an allusion to a young animal = protoconch, in reference to the large size of the protoconch.

Remarks: Turbonilla enna Bartsch in Dall, 1927, (Pimenta & Absalão in press: fig. 35 [holotype]) is the most similar species in the western Atlantic to T. megascymna . However, T. megascymna has more convex whorls with lower and less­defined axial ribs than T. enna . Moreover, T. enna has interspaces as wide as the ribs, and the ribs stop abruptly at the periphery of body whorl while in T. megascymna the interspaces are twice or more as wide as the ribs, and the axial ribs disappear at the base. Finally, the protoconch of T. megascymna is significantly larger than that of T. enna .

Figures

FIGURES 1 ­ 7. 1 ­ 3. Turbonilla virgulinoi n. sp., holotype (MNRJ 9823). 1: whole shell, length 1.8 mm; 2: base detail; 3: protoconch detail. Scale bar = 100 µm. 4 ­ 7. Turbonilla megascymna n. sp., holotype (IBUFRJ 12703). 4: whole shell, length 2.3 mm; 5: protoconch detail; 6: base detail; 7: spiral micro­sculpture. Scale bar = 100 µm.