Terebra assu Simone, 2012

Simone, Luiz Ricardo L. & Cunha, Carlo M., 2012, Taxonomic study on the molluscs collected in Marion-Dufresne expedition (MD 55) to SE Brazil: Xenophoridae, Cypraeoidea, mitriforms and Terebridae (Caenogastropoda), Zoosystema 34 (4), pp. 745-781 : 772-774

Terebra assu Simone n. sp.

( Fig. 10 A-E)

TYPE MATERIAL. — Holotype: Brazil, Espírito Santo, off Conceição da Barra, continental slope of Abrolhos , 18°59’S, 37°50’W, 295 m depth, MNHN 25244 ( Fig. 10A , C-E) ( MD55 , stn DC75 , Bouchet, Leal & Métivier coll., 27.V.1987).

Paratypes:same data as holotype, MNHN 25242, 1 shell, MZSP 102598, 1 shell ( Fig. 10B ).

TYPE LOCALITY. — Brazil, Espírito Santo, off Conceição da Barra, continental slope of Abrolhos, 18°59’S, 37°50’W, 295 m depth ( MD 55, stn DC 75).

DISTRIBUTION. — Known only for the type locality.

ETYMOLOGY. — The specific epithet refers to the elongation of the shell, from the Tupi native language “açu” (transliterated to assu), meaning elongated, slender.

DIAGNOSIS. — Narrow shell with pale yellowish colour. Protoconch paucispiral, with one whorl. Sculpture reticulate strong in 4-5 first teleoconch whorls, becoming weaker, with predominance of axial threads in remaining whorls. Subsutural ridge somewhat prominent.

DESCRIPTION

Shell: up to 9.8 mm long, width c. ∕₅ of length, spire angle c. 13°. Colour predominantly white, with yellowish band in middle level of each whorl, comprising c. 80% of each whorl area ( Fig. 10A, B ); band margins unclear. Protoconch simple, smooth, of one whorl ( Fig. 10D, E ); width c. 35% of maximum teleoconch width; length c. 16% of shell length. Limit between protoconch and teleoconch indistinct ( Fig. 10E ). Teleoconch with up to 10 whorls; profile weakly convex, suture clear but shallow. Sculpture of first teleoconch whorls with only strong axial threads, c. 10 per whorl, each thread smooth, with upper node, between both threads length equivalent to double their width; in third whorl spiral threads gradually appearing, becoming stronger in following whorls, equally predominating as axial threads; after sixth teleoconch whorl sculpture becoming weak, spiral threads almost disappearing, axial threads somewhat predominating, space between axial threads 3-4 times wider than threads; four spiral threads and 7-8 axial threads in penultimate whorl. Subsutural thread somewhat prominent, being c. 50% larger than remaining threads; in first whorls mainly marked by nodes of axial threads, after 3-4 teleoconch whorls becoming similar to remaining threads. After sixth teleoconch whorl sculpture gradually becoming weaker than preceding whorls, both spiral and axial threads. In last whorl, c. 15 axial threads in penultimate whorl, with interspaces c. 3 times wider than threads width; 5-6 spiral threads in penultimate whorl, being inferior threads narrower and closer with each other than upper threads; subsutural thread of similar size as remaining threads. Sculpture of peri-umbilical area composed of 7-8 spiral liration in upper half, and series of low transverse scales in inferior half ( Fig. 10A, C ). Aperture orthocline, oval, about twice longer than wide. Outer lip thick, simple, with blunt notches corresponding to spiral sculpture. Inner lip with weak callus; parietal region in upper third, marked by abrupt curve in c. 40°; siphonal region in inferior ⅔, somewhat straight and vertical, except for region close to anterior end, with bright curve to left ( Fig. 10B, C ). Canal short, slightly curved to left.

MEASUREMENTS (in mm). — Holotype: 9.8 × 2.0; paratype MZSP 102598 : 8.3 × 1.8; paratype MNHN 25242 : 5.4 × 1.6.

HABITAT. — Sandy-mud bottoms, 295 m depth.

REMARKS

Terebra assu Simone n. sp. differs from the other closely-related species in being small (smaller than 10 mm, while others usually reach 20 mm, such as T. leptapsis and T. crassireticula – Fig. 11 I-L) in an equivalent number of whorls; with a pale yellowish pigmentation in middle region of each whorl (most species are pure white – T. crassireticula , T. alagoensis – Figs 10 F-I; 11A-D, L; uniform pale brown – T.doellojuradoi , T. leptapsis – Fig.11 E-K; but it is somewhat similar to T. simonei Lima,Tenório & Barros, 2007 : figs 1-6); and by the weaker sculpture of the last whorls both in number and in size. This last character produces a feeble reticulate sculpture on the last whorls, in such the axial threads surrounds 15 on the penultimate whorl, while the remaining species in the T. doellojuradoi complex normally possess over 25. The protoconch is proportionally broader than the other closer species. The aperture is more elongated and narrow ( Fig. 10 A-C) than those of the other close species, except for T. crassireticula ( Fig. 11L ). The subsutural spiral thread is only more developed in the first teleoconch whorls, resembling T. alagoensis ( Figs 10 F-I; 11A-D); the first whorls of T. assu Simone n. sp. can be distinguished from those of T. alagoensis in having more elongated whorls with a more concave profile.

Terebra alagoensis Lima, Tenório & Barros, 2007 ( Fig. 10 F-I; 11A-D)

Terebra alagoensis Lima, Tenório & Barros, 2007: 66 , figs 13-17. — Rios 2009: 358, fig.937. — Rosenberg 2009.

TYPE MATERIAL ( EXAMINED). — Holotype: Brazil, continental slope off Alagoas, 10°05’57’’S, 35°46’24’’W, 720 m, MZSP 84238 ( Fig. 11 A-D) ( R / V Natureza, stn D-29, 28.X.2000).

OTHER MATERIAL EXAMINED. — Brazil, Espírito Santo, continental slope of Abrolhos, off Rio Doce, Abrolhos bank, 19°34’S, 38°55’W, 340-360 m depth, MNHN, 10 shells, MZSP 102613, 2 shells ( Figs 10F, H, I ) ( MD 55, stn CB 92, Bouchet, Leal & Métivier coll., 29. V.1987). — East of São Tomé Cape, 21°31’S, 40°08’W, 295-300 m depth, MNHN, 10 shells, MZSP 102607, 3 shells ( Fig. 10G ) ( MD 55, stn CB 96, 31. V.1987).

TYPE LOCALITY. — Brazil, continental slope off Alagoas, 10°05’57’’S, 35°46’24’’W, 720 m ( R / V Natureza, stn D-29).

DISTRIBUTION. — From Alagoas to Espírito Santo.

DESCRIPTION

See Lima et al. (2007: 66).

MEASUREMENTS (in mm). — Holotype: 10.5 × 2.8; MNHN (stn CB92) (1): 4.9 × 1.6; MZSP 102607 (1): 4.1 × 1.4.

HABITAT. — Sandy-mud, 340-720 m depth.

REMARKS

Terebra alagoensis is very distinct from the remaining T. doellojuradoi complex by its large subsutural spiral thread, producing almost a shoulder. The whorls have their periphery almost flat and vertical, giving it a scalariform effect in the spire. The MD55 material ( Fig. 10 F-I) is constituted of a single lot with 13 specimens, all of which considerably younger than the holotype ( Fig. 11 A-D); the largest specimen is 4.9 mm long; although the shell characters clearly allowed the identification. This new record considerably expands the geographic distribution of this species at almost 800 km southward. However, despite the distance, the environment and depth are equivalent.

Another interesting feature of Terebra alagoensis is the relatively wide protoconch ( Figs 10H, I ; 11B, C ), comprising a wide portion of the shell apex ( Figs 10F, G ; 11A ). The transition with teleoconch is not so clear ( Figs 10I ; 11C ), and the first teleoconch whorl is marked by pure axial, lyrate sculpture ( Figs 10 G-I; 11B, C). The spiral sculpture gradually appears after the first teleoconch whorl. The aperture of Terebra alagoensis is marked by a pair of oblique folds in the middle level of the inner lip ( Fig. 11A, D ), which are also evident, but lower, in the younger specimens ( Fig. 10F, G ). This is not a normal pattern for the T. doellojuradoi complex.

Figures

FIG. 10. — Terebrids: A, Terebra assu Simone n. sp, holotype MNHN 25244, frontal view (L 9.8 mm); B, paratype MZSP 102598, profile view (L 8.3 mm); C, holotype, detail of last whorl, frontal view; D, E, first whorls in two opposite views; F, T. alagoensis Lima, Tenório & Barros, 2007, MNHN (stn CB92), frontal view (L 4.9 mm); G, MZSP 102607 (1), frontal view (L 4.1 mm); H, I, protoconch of Figure F in two opposed views.

FIG. 11. — Terebrids:A, Terebra alagoensis Lima,Tenório & Barros, 2007,holotype MZSP 84238 (L 10.5 mm), frontal view;B, C, details of apical region in two opposite views; D, detail of last whorl, frontal-slightly profile view; E, Terebra doellojuradoi, holotype MACN 23439, frontal view (L 10.2 mm); F, same, detail of protoconch and first whorls; G, same, profile view; H, paratype MACN 24278, frontal-slightly profile view (L 8.5 mm); I, T. leptapsis, holotype MZSP 28704, frontal view (L 16.0 mm); J, detail of protoconch in SEM; K, dorsal view; L, T. crassireticula, holotype MZSP 27930 (L 22.0 mm).