Aclis costai, Souza & Araújo & Pimenta, 2024

Souza, Leonardo Santos De, Araújo, Tarciso Almeida De & Pimenta, Alexandre Dias, 2024, Taxonomic review of Aclis Lóven, 1846 (Gastropoda, Eulimidae) from Brazil with notes on other congeners from the western Atlantic and Saint Helena, Zootaxa 5433 (4), pp. 451-499 : 472-474

Aclis costai sp. nov.

Fig. 12

Type material. Holotype. MNRJ 23777 ; R/ V Ocean Stalwart coll., 28/vii/2019 . Paratypes: Brazil: Espírito Santo state: South of Abrolhos Bank , JOPS-II-8 sta. 3228; 19°45′30″S, 38°45′48″W, 1100 m; 14/iv/1995; R/V Victor Hensen ; MNRJ 22634 [1]; Rio de Janeiro state: Campos Basin ; 22°18′53″S, 40°11′59″W, 200 m; 18/xii/2004; Supply Boat Astro Garoupa; MNRJ 33559 [1†]; Santa Catarina state: PADCT 6611; W, MNRJ 60249 [2]; MNRJ 23603 [1]; off Itajaí ; 27°02′14″S, 46°53′51″W, 200 m; vii/2004; MNRJ 26730 [1†].

Type locality. Brazil: Rio de Janeiro state: PCR BS 4 sta. G6; 23°48′57.96″S, 42°40′31.8″; 404 m.

Material examined: The types and: Brazil: Rio de Janeiro state: Campos Basin ; 22°18′53″S, 40°11′59″W, 200 m; 18/xii/2004; Supply Boat Astro Garoupa col.; MNRJ 35546 [17†]; Revizee Sul sta. 6660; MNRJ 28256 [1†]; Santos Basin ; 24°20′40″S, 43°50′21″W, 610 m; 29/i/2009; MNRJ 35926 [4†]; São Paulo state: Revizee Sul sta. 6671; MNRJ 28257 [1†]; PADCT sta. 6587; MNRJ 28246 [1†]; MNRJ 28255 [2†];

Paraná state: Revizee Sul sta. 6703; MNRJ 28260 [1†]; Revizee Sul sta. 6685; MNRJ 28258 [4†]; PADCT sta. 6642; MNRJ 28252 [1†]; Revizee Sul sta. 6653; MNRJ 28254 [1†]; Revizee Sul sta. 6652; MNRJ 28253 [4†]; Santa Catarina state: Revizee Sul sta. 6695; MNRJ 28259 [3†]; PADCT sta. 6595; MNRJ 28247 [3†]; off Itajaí ; 150 m; 28/i/2005; MNRJ 28843 [3†]; PADCT sta. 6635; MNRJ 28251 [9†]; PADCT sta. 6601; MNRJ 28248 [5†]; PADCT sta. 6608; MNRJ 28249 [23†]; type locality; MNRJ 28250 [9†].

Etymology. Named after our dear friend, Dr. Paulo Márcio Santos Costa, who donated part of the specimens studied here.

Description. Shell vitreous or whitish, tall, subcylindrical, with an obtuse apex, reaching about 5.1 mm long, 1.7 mm wide. Protoconch globose, subcylindrical, about 2.0 whorls, 580 μm wide, smooth, transition to teleoconch marked by a gentle incremental scar. Teleoconch reaching about five whorls, strongly convex outline; suture deep, well impressed, sloping; surface glossy, presenting faint microscopic spiral threads in subsutural zone of each whorl, growth lines well-impressed, incremental scars strongly demarcated, appearing at irregular intervals. Last whorl about 45% of total length, broad; base rounded. Aperture high, elliptical in shape, about 65% of body whorl length, strongly expanded laterally, rounded and with a concavity in the anterior edge, acute posteriorly; outer lip thickened, raised suture near adapical margin, strongly opisthocline, gradually advancing forward, rectilinear; inner lip thick, reflected. Umbilical fissure usually present.

Measurements. Holotype, MNRJ 23776: 7 whorls; SL= 4.8 mm; BWL= 2.2 mm; AL= 1.4 mm; SW= 1.6 mm; AW= 1.0 mm. Paratype, MNRJ 33559: 7 whorls; SL= 5.1 mm; BWL= 2.4 mm; AL= 1.6 mm; SW= 1.7 mm; AW= 1.1 mm. Paratype, MNRJ 22634: 6 whorls; SL= 3.8 mm; BWL= 2.0 mm; AL= 1.3 mm; SW= 1.5 mm; AW= 0.9 mm. Paratype, MNRJ 60249: 4 whorls; SL= 2.7 mm; BWL= 1.6 mm; AL= 0.9 mm; SW= 1.1 mm; AW= 0.6 mm.

Remarks. This species is known only from empty shells, which are frequent in depths close to the continental shelf break and upper slope. The deepest record was found in 1100 m, off the coast of Espírito Santo state, but the single shell (paratype MNRJ 22634) was probably carried out by turbidity currents.

Aclis costai sp. nov. has faint microscopic spiral striae in the subsutural region of each whorl ( Fig. 12I ) like other Aclis species. However, the axial growth lines are more conspicuous than the spiral sculpture. The general shape of the shell, protoconch and aperture also suggests the present generic classification. The shell shape ( Fig. 12A–F ) and the concavity, with a flattened surface in the anterior area of the aperture ( Fig. 12G ) are diagnostic, differing the present species from most of his congeners. The anterior part of the aperture is commonly damaged, giving the appearance of a siphonal canal (e.g., Fig. 12A, C, D ), but it is a flattened area that could be recognized in shells with an undamaged aperture in the lower part ( Fig. 12E ).

Aclis costai sp. nov. resembles Aclis georgiana ( Fig. 19G–H ) but can be distinguished by having a much broader length and width, a faster increase in diameter and a wider aperture, which is more expanded laterally and anteriorly than in A. georgiana .

Geographic Distribution. Brazil: Espírito Santo, Rio de Janeiro, São Paulo, Paraná, Santa Catarina. From 70 m to 1100 m.

Figures

FIGURE 12. Aclis costai sp. nov. A, B. Holotype, MNRJ 23776. C. Paratype, MNRJ 22634. E, F, H, I, K. Paratypes, MNRJ 26730. D, G, J. Paratype, MNRJ 33559. A, C–E. Shell in frontal view. B, F. Shell in lateral view. G, H. Detail of body whorl in frontal and lateral views, respectively. I. Detail of the teleoconch surface, arrows indicate microscopical spiral striae. J. Protoconch in apical view; arrow indicates transition protoconch-teleoconch.. K. Detail of apical whorls. Scale bars: A–F. 1 mm; G–H. 500 μm; I. 50 μm; J–K. 200 μm.

FIGURE 19. A–D. Aclis eolis Bartsch, 1947: Holotype, USNM 573617. A. Shell in frontal view. B. Shell in lateral view. C. Detail of apical whorls. D. Detail of the body whorl in frontal view. E–F. Aclis hendersoni Dall, 1927: E, F. Holotype, USNM 333465; E. Shell in frontal view. F. Protoconch in apical view. G–H. Aclis georgiana Dall, 1927: Holotype, USNM 108020. G. Shell in frontal view. H. Protoconch in apical view. Scale bars: A, B, E, G. 1 mm; C, F, H. 200 μm, D. 500 μm. Credits: E–H. USNM.