Ceratia francisca, 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 : 184

Ceratia francisca n. sp. ( Figure 1 )

Type material. Holotype—1 shell ( Fig. 1 ), MZSP 122158 from type locality; paratypes—2 shells, MNRJ 34.455; 1 shell, MNHN IM- 2014-6056; 2 shells, UFS-MOL-GAS, 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, underwater canyon of the São Francisco River, 10°43'13.2''S, 36°11'59.5''W, 1275 m, 29–30 August 2012.

Etymology. The specific epithet is derived from the locality where the species was collected from the continental slope off Sergipe.

Description. Shell minute to small (about 1.5 to 2.4 mm long), rather delicate, whitish to light cream, elongate-conic ( Fig. 1 A–B). Apex flattened ( Fig. 1 D). Protoconch smooth, with about two whorls: first whorl planar and second whorl then descending slightly ( Fig. 1 D–E). Protoconch-teleoconch transition marked with very fine axial grooves (transitional varix absent) ( Fig. 1 E). Spire 30 to 40% of total length ( Fig. 1 A–B). Teleoconch with about 3.75 very inflated, rounded whorls which increase gradually in size (broken specimen with very large body whorl probably with more than 3.75 whorls on teleoconch); teleoconch whorls with evenly convex profile or may present very slight subsutural angle on penultimate to body whorl ( Fig. 1 A), deeply impressed and minutely channeled suture ( Fig. 1 A–E). First teleoconch whorl with many obsolete to very faint spiral threads and sparse axial growth lines increasing in strength towards next whorls ( Fig. 1 D). Penultimate and body whorl sculptured predominantly with numerous, low, fine, faint, very slightly shaky, rather equally and narrowly spaced spiral threads crossed by sparse, rather prosocline, low, fine, irregularly spaced axial growth threads and fine axial grooves ( Fig. 1 C). Spiral and axial threads visible under a stereomicroscope. Some spiral and axial threads are more pronounced than others ( Fig. 1 C). Intersection of sculptures indistinct. Body whorl very inflated, oval-elongated, about 60 to 70% of total length and with about 67 spiral threads ( Fig. 1 A–B). Aperture simple, elongate, D-shaped, large (about 1/4 to 1/3 of total length of shell), anterior margin rounded, posterior margin angled ( Fig. 1 A). Inner lip straight, elongated, rather thin, slightly separated from parietal wall. Outer lip prosocline, rather thin; external varix absent. Parietal region thin. Imperforate or with very narrow umbilicus (as chink) ( Fig. 1 A).

Geographical distribution. Known only from the continental slope of the state of Sergipe, northeastern Brazil.

Remarks. Ceratia francisca n. sp. has a very distinctive shell morphology in comparison to the other Brazilian species, C. pachia . The new species differs from C. pachia primarily in having an elongate-conic shell, an elongated spire, an oval body whorl and a deeply impressed suture. Ceratia pachia is distinguished by the ovate-conic shell, short spire, rounded body whorl and scarcely impressed suture (see Watson 1886: 602, pl. XLV, fig. 7; Rios 2009: 82).

Ceratia francisca n. sp. most closely resembles C. proxima . According to Bouchet & Warén (1993: 703), a neotype (USNM 183132) was designated for this species by Warén (1980: 23). Both species have a shell with identical elongateconic outline and teleoconch whorls with the same constricted shape due to the deep suture. Ceratia francisca n. sp. and C. proxima also share distinct spiral threads on the teleoconch whorls, a D-shaped aperture and a very narrow umbilicus in shape of fissure. Furthermore, these species have about two protoconch whorls. Ceratia francisca n. sp. differs in having about 67 faint spiral threads on the last whorl, while C. proxima has about 30 more pronounced spiral threads on the penultimate and body whorl. The inner lip is clearly straight and slightly separated from the parietal wall in C. francisca n. sp., but is slightly curved and connected the parietal wall on the upper portion in C. proxima . The new species has a number of fine axial threads on the teleoconch whorls. In contrast, C. proxima has sparse, rather inconspicuous axial threads on the surface. The remarks presented herein on the shell morphology of C. proxima are based on Ponder (1984: 53, fig. 18A–C), Bouchet & Warén (1993: 702, figs 1655–1656) and Warén (1996: 212, fig. 11D).

Figures

FIGURE 1. Ceratia francisca n. sp. (holotype, MZSP 122158): A. ventral view; B. lateral view; C. detail of ornamentation and suture; D. lateral view of protoconch; E. apical view of protoconch (arrow pointing to the transition margin between the protoconch and teleoconch). Scale bars: A. 500 µm, B – C. 200 µm, D. 100 µm, E. 50 µm.