Ceratia sergipana, Lima, Silvio Felipe B., Júnior, Ivan Cardoso L., Guimarães, Carmen Regina P. & Dominguez, José Maria L., 2016

Lima, Silvio Felipe B., Júnior, Ivan Cardoso L., Guimarães, Carmen Regina P. & Dominguez, José Maria L., 2016, New deep ocean Iravadiidae of the genus Ceratia (Caenogastropoda: Truncatelloidea) from an underwater canyon and adjacent regions of the southwestern Atlantic (northeastern Brazil), Zootaxa 4066 (2), pp. 183-188 : 185-187

Ceratia sergipana n. sp. ( Figure 2 )

Type material. Holotype—MZSP 121795 ( Fig. 2 A), BRAZIL, state of Sergipe, station SED 3 DN4R2, 10°53'25.7"S, 36°29'25.9"W, 405 m, box corer (R/V 'Seward Johnson' collector, 20–21 March 2013); paratypes—1 shell, MNHN IM- 2014-6057; 1 shell, MZSP 122159; 1 shell, UFS-MOL-GAS, BRAZIL, state of Alagoas, station SED 3 AN4R1, 10°19'40.5"S, 35°55'50.7"W, 420 m, box corer (R/V 'Seward Johnson' collector, 13 March 2013); 1 shell, UFS-MOL- GAS, BRAZIL, state of Alagoas, station SED 3 BN 4R2, 10°32'07.1"S, 36°05'11.5"W, 391 m, van veen (R/V 'Seward Johnson' collector, 0 6 April 2013); 2 shells, MNRJ 34.431 ( Fig. 2 B–F), BRAZIL, state of Sergipe, underwater canyon of the São Francisco River, 10°43'13.2''S, 36°11'59.5''W, 1275 m, 29–30 August 2012; 1 shell, UFS-MOL-GAS, BRAZIL, state of Sergipe, station SED 3 DN4R2, 10°53'25.7"S, 36°29'25.9"W, 405 m, box corer (R/V 'Seward Johnson' collector, 20–21 March 2013); 1 shell, MZSP 122160, BRAZIL, state of Sergipe, station SED 3 FN4R1, 11°11'21.4"S, 36°52'17.2"W, 399 m, box corer (R/V 'Seward Johnson' collector, 24 March 2013).

Type locality. BRAZIL, Northeastern Brazil, continental slope of the state of Sergipe, 10°53'25.7"S, 36°29'25.9"W, 405 m, 20–21 March 2013.

Etymology. “ Sergipana ” is the general designation for individuals born in the state of Sergipe, Brazil.

Description. Shell minute to small (about 1.6 to 3 mm long), thin, delicate, white to semitranslucent white, ovateconic to conical ( Fig. 2 A–C). Apex flattened ( Fig. 2 E). Protoconch smooth, with about two whorls: first whorl planar and second whorl then descending very slightly (both with minute subsutural wrinkles); very fine, faint, strongly sinuous axial grooves/threads near transition to teleoconch (transitional varix absent) ( Fig. 2 E–F). Spire about 34 to 40% of total length ( Fig. 2 A–C). Teleoconch with 3.25 to 5 inflated, rounded, constricted whorls, which increase rather moderately in size (except fifth whorl, which increases rather conspicuously in size); teleoconch whorls with evenly convex profile, deeply impressed suture ( Fig. 2 A–C). First teleoconch whorl sculptured with inconspicuous to well-developed spiral threads only on suprasutural region and inconspicuous to sparse, very thin, sinuous axial threads/grooves ( Fig. 2 B–C). Second teleoconch whorl sculptured with up to 12 well-developed, low, slightly shaky, rather equally and widely spaced spiral threads (few threads may be present only on suprasutural region) crossed by numerous, irregularly positioned, very faint axial growth striae/threads ( Fig. 2 B–C). Third, fourth and fifth teleoconch whorl with 13 to 16, 13 to 18 and 18 to 20 well-developed spiral threads (respectively) and very thin axial threads ( Fig. 2 A–C). Spiral threads on fourth and fifth whorl more widely spaced compared to initial whorls. End of fifth whorl may present slightly sinuous axial ribs and inconspicuous spiral threads ( Fig. 2 A). Intersection of sculptures indistinct. Body whorl oval, inflated, about 60% of total length. Base ornamented with 8 to 11 spiral threads. Aperture simple, oval, large (about 1/3 of total shell length), anterior margin rounded, posterior margin moderately angled. Peristome very thin. Inner lip smooth, very thin, moderately curved, separated from parietal wall (except on upper portion). Outer lip slightly sinuous, very thin; external varix absent. Parietal region thin, sub-flattened. Umbilicus (as chink) moderately narrow to very narrow ( Fig. 2 A–B).

Geographical distribution. Known from the continental slope of the states of Alagoas and Sergipe, northeastern Brazil.

Remarks. The new species and Ceratia pachia share an ovate-conic shell, a large oval aperture, which is distinctly angled posteriorly, a thin inner lip and a chinked umbilicus. However, C. sergipana n. sp. differs from C. pachia in also having a conical shell (with 4 to 5 teleoconch whorls), the teleoconch whorls moderately increasing in size and regularly convex, an oval body whorl and moderately curved inner lip. In C. pachia , the teleoconch whorls increase rapidly in size and have a subsutural furrow, the body whorl is rounded and the inner lip is straight. The suture is deeply impressed in C. sergipana n. sp. and very slightly impressed in C. pachia . The remarks presented herein on the shell morphology of C. pachia are based on Watson (1886: 602, pl. XLV, fig. 7) and Rios (2009: 82).

Ceratia sergipana n. sp. resembles C. francisca n. sp. and C. proxima in having about two protoconch whorls and inflated, constricted teleoconch whorls due to the presence of a deeply impressed suture. In Ceratia sergipana n. sp., the aperture is oval, the shell is ovate-conic to conical, sculptured with well-developed and widely spaced spiral threads on the penultimate (13 to 18 threads) and last whorl (18 to 20 threads). In contrast, C. proxima and C. francisca n. sp. have a D-shaped aperture, an elongate-conic shell sculptured with very faint, narrowly spaced spiral threads. These Atlantic congeners develop about 30 and 67 spiral threads (respectively) on the last whorl. Furthermore, the new species has a moderately curved inner lip, while C. francisca n. sp. and C. proxima have a rather straight inner lip.

Figures

FIGURE 2. Ceratia sergipana n. sp. (A. holotype, MZSP 121795; B – F. paratype, MNRJ 34.431): A and B. ventral view; C. lateral view; D. detail of ornamentation and suture; E. lateral view of protoconch; F. apical view of protoconch (arrow pointing to the probable transition margin between the protoconch and teleoconch). Scale bars: A. 1 mm, B – C. 500 µm, D – E. 100 µm, F. 50 µm.