Scissurella azorensis, Nolt, Jaya M., 2008

Nolt, Jaya M., 2008, A new species of Scissurella from the Azores with discussions on Sinezona semicostata Burnay & Rolán, 1990 and Sinezona cingulata (O. G. Costa, 1861) (Gastropoda: Vetigastropoda: Scissurellidae), Zootaxa 1678, pp. 51-62 : 54-56

Scissurella azorensis new species

( Fig. 1 , Fig. 2 A)

Holotype. MNHN Moll 9640, gold coated.

Paratypes. 2 MNHN Moll 9641, from type locality. 1 MCZ 356976, Pedra Furada, Baia do Alcaide, Silveira, Terceira Island, Azores 38°39’ N, 27°14’ W, all gold coated.

Type locality. Santa Maria Island, off Ponta do Marvão, Azores. 0–1 m, in rocks. June 1990. Leg. S. and C. Gofas. 36°56’N, 25°08’W.

Etymology. Named for the provenance from the Azores.

Description. Shell small to 0.75 mm, trochoid with flat spire, one fourth wider than high, whitish. Protoconch 120 µm long, 1.16–1.2 whorls, 24–28 strong to irregular axial cords, axials on outer margin of protoconch not extending full width, no apertural varix, apertural margin rounded. Teleoconch I slightly greater than one whorl, approximately 18–20 strong axial cords, fine irregular lamellae between axials, no spiral sculpture. Teleoconch II 0.75 whorls, with nine weaker axial cords, fine irregular lamellae, no spiral sculpture. Shoulder angled down from coiling axis with fine irregular lamellae. Base rounded, with 18–25 weak axial cords, fine irregular lamellae between axials. Umbilicus open with marginal carina, weak axial lines on base. Selenizone, slit above periphery, moderately keeled. Aperture subquadratic, edge slightly projecting. Animal unknown.

Distribution. Only known from the type material from the Azores.

Comparisons. The holotype ( Fig. 1 A) is a mature Scissurella spp. and not a juvenile Sinezona spp. because it shows an open slit with the long angled shoulder and descending last quarter whorl. Compared to the other species of the region, Sci. azorensis is distinguished by the protoconch sculpture which contains axial cords on the outer margins only, an open umbilicus region, teleoconch I is slightly greater then one whorl and the numerous strong axial cords over the entire shell.

Scissurella lobini ( Burnay & Rolán, 1990) from the Cape Verde Islands ( Fig. 3 A) and Scissurella redferni ( Rolán, 1996) from the Caribbean ( Fig. 3 B) both differ from Sci. azorensis in that the protoconch has fewer axial cords (24–28 in Sci. azorensis , 14–18 in Sci. lobini and Sci. redferni ), the axials are more uniform in shape and the bases of Sci. redferni and Sci. lobini have spiral threads. Scissurella costata d’Orbigny, 1824 from the Mediterranean ( Fig. 3 C) has a flattened spire, apertural margin of the protoconch is sinusoid, teleoconch sculpture contains thin irregular axial lines and spiral threads on shoulder and base, and teleoconch II has approximately 1.3 whorls. Since Sinezona and Scissurella spp. may be difficult to distinguish in juvenile stages due to the incomplete closure of the slit in the foramen, comparisons are also made with Sinezona spp. from the Atlantic-Mediterranean region. Sinezona cingulata ( O.G. Costa, 1861) from the Mediterranean ( Fig. 2 B) has a protoconch sculpture with approximately 15 strong axial cords that cover more than half the width. Teleoconch I has fewer then one whorl, with 14 axial cords and the umbilicus is very narrow. Sinezona semicostata Burnay & Rolán, 1990 from the Cape Verde Islands ( Fig. 4 A) most closely resembles Sci. azorensis but has approximately 12 protoconch axial cords over more than half the width and teleoconch I has fewer than one whorl and as a member of Sinezona , the foramen is closed in mature specimens. Sinezona confusa Rolán & Luque, 1994 from the Caribbean ( Fig. 4 B) has protoconch sculpture with approximately 14 axial cords that cover more than half the width, an apertural varix and spiral threads on teleoconch I and II.

Figures

FIGURE 1. Scissurella azorensis n. sp., SEM-micrographs of shells in frontal, umbilical, apical and detail on protoconch (apical view). A. Holotype MNHN Moll 9640, B., C. Paratypes MNHN Moll 9641. Scale bars: shells 200 µm, protoconch 100 µm.

FIGURE 2. SEM-micrographs of shells in frontal, umbilical, apical and detail on protoconch (apical view). A. Scissurella azorensis n. sp., paratype MCZ 356976. B. Sinezona cingulata AMS C. 380708. Benzu, Spain 35.91 ° N, 5.40 ° W. C. Sinezona depressa syntype BMNH 1911.7. 17.21. Madeira Islands 32.66 ° N, 16.75 ° W. Scale bars: shell 200 µm, protoconch 100 µm.

FIGURE 3. SEM-micrographs of shells in frontal, umbilical, apical and detail on protoconch (apical view). A. Scissurella lobini paratype BMNH 1991122. Porto Novo, Sto Antao Island, Cape Verde Islands 17.067 ° N, 25.083 ° W. B. Scissurella redferni paratype BMNH 1996100. Chub Rock, Abaco Island, Bahamas, 26.467 ° N, 77.083 ºW. C. Scissurella costata AMS 406387. Sardinia, Italy 41.233 ° N, 9.133 ° E. Scale bars: shell 200 µm, protoconch 100 µm.

FIGURE 4. SEM-micrographs of shells in frontal, umbilical, apical and detail on protoconch (apical view). A. Sinezona semicostata paratype MNHN Moll 5280. Cape Verde Archipelago, Boavista Island 15 ° N, 23 ° W. B. Sinezona confusa paratype BMNH 1994094 Playa Baracoa, Cuba 23 ° 03 ’ N, 82 ° 34 ’ W. C. Sinezona fayalensis MNHN. Santa Maria Island, Azores 36.95 ° N, 25.11 ° W. Scale bars: shell 200 µm, protoconch 100 µm.