Aclis aff. conula Dall, 1927

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 : 469-472

Aclis aff. conula Dall, 1927

Fig. 11

Material examined. Brazil: Espírito Santo state: off Piúma; 1993; F. Pitombo leg.; IBUFRJ 8497 [1†]; Rio de Janeiro state; HAB 16 sta. H3; MNRJ 17688 [3†]; Geomar XII sta. 90; IBUFRJ 7584 [1†]; HAB 16 sta. G3; MNRJ 16712 [4†].

Characterization. Shell tall, conical, spire angle 23°–31°, reaching about 4.0 mm long, 1.5 mm wide, eight whorls, yellowish-brown in color. Protoconch conical, tip narrow, about 2.0 whorls, 340 μm wide, surface smooth. Teleoconch with moderately convex whorls, surface glossy presenting faint microscopical spiral striae and strong incremental scars with irregular intervals. Body whorl about half the total length, base rounded; aperture high, about 60% of body whorl length, strongly expanded laterally, rounded anteriorly, acute posteriorly; outer lip thin, strongly opisthocline, sinuous, strongly advanced close to distal area; inner lip thin, reflected. Umbilicus present, bordered by a sharp edge.

Measurements. IBUFRJ 7584: 7 whorls; SL= 2.94 mm; BWL= 1.59 mm; AL= 1.03 mm; SW= 1.34 mm; AW= 0.72 mm. IBUFRJ 8497: 8 whorls; SL= 4.04 mm; BWL= 1.99 mm; AL= 1.18 mm; SW= 1.50 mm; AW= 0.80 mm.

Geographic Distribution. Brazil: Espírito Santo, Rio de Janeiro. From 71 m to 76 m.

Remarks. Aclis aff. conula is noticeably different from the other species of Aclis from surrounding areas by the yellowish-brown color, a markedly oval aperture and inflated teleoconch whorls ( Fig. 11A, F ). The umbilicus is also notable because it is broad and bordered by a sharp edge ( Fig. 11C ). The teleoconch has the spiral micro striae typical of the genus but is weaker than commonly found in Aclis and more spread along the teleoconch surface ( Fig. 11D, E ). The species presents a variation in the spire angle; the shell of IBUFRJ 7584 ( Fig. 11A ) is more inflated than the shell of IBUFRJ 8497 ( Fig. 11F ) (spire angle: 31° vs. 23°).

Aclis aff. conula closely resembles Aclis conula Dall, 1927 ( Fig. 20A–C ), from the continental slope off Georgia, USA. Both taxa have about 2.0 protoconch whorls and the maximum diameter is slightly similar (IBUFRJ 7584 and holotype of A. conula , respectively: 340 μm vs. 310 μm). However, the protoconch of Aclis aff. conula is more pointed and has a considerably narrower tip (first whorl diameter: 180 μm vs. 255 μm). Moreover, Aclis aff. conula has a wider umbilicus which is bordered by a sharp edge while it is more rounded in A. conula . We can also add that Aclis aff. conula is restricted to the continental shelf, while A. conula is known only from the continental slope. These taxa possibly differ in color since Dall (1927) described A. conula as whitish. However, if the shell of A. conula was found in a worn condition it remains doubtful.

Aclis aff. conula can be distinguished from Aclis pyramida Dall, 1927 ( Fig. 20D–F ), from the continental slope off Georgia, USA, by having a less globular shape, a slower increase in diameter and a narrower protoconch. Both species reach about 2.0 protoconch whorls, but Aclis aff. conula has a smaller tip (first whorl: 180 μm vs. 284 μm) and maximum diameter (340 μm vs. 415 μm).

Aclis aff. conula differs from A. rushi ( Fig. 17C–E ) and A. tenuis ( Fig. 18A, B ) because it has a broader shape, a wider umbilicus, an opisthocline and more advanced outer lip.

We refrain from describing Aclis aff. conula as a new species because of the lack of sufficient material.

Figures

FIGURE 11. Aclis aff. conula Dall, 1927. A–E. IBUFRJ 7584. F–J. IBUFRJ 8497. A, C, F, G. Shell in frontal view. B, H. Shell in lateral view. D, E. Detail of teleoconch surface; square in D indicates detail in E. I. Detail of apical whorls. J. Protoconch in apical view; arrow indicates transition protoconch-teleoconch. Scale bars: A–C, F–H. 1 mm; D–E. 50 μm; I–J. 200 μm.

FIGURE 17. A, B. Aclis marguerita (Bartsch, 1947): Holotype, USNM 108019. A. Shell in frontal view; the two fragments in A belongs to the broken holotype. B. Detail of body whorl in lateral view. C–E. Aclis rushi Bartsch, 1911: Holotype, USNM 82973. C. Shell in frontal view. D. Shell in lateral view. E. Detail of apical whorls. Scale bars: A, C–D. 1 mm; B. 500 μm; E. 200 μm.

FIGURE 18. A, B. Aclis tenuis Verrill, 1882: Holotype, USNM 44821. A. Shell in frontal view. B. Shell in lateral view. C, D. Aclis fernandinae Dall, 1927: Holotype, USNM 108047. C. Shell in frontal view. D. Protoconch in apical view. E–I. Aclis verrilli Bartsch, 1911: E–G. Holotype, USNM 44811; H–I. Holotype of Aclis tanneri (Bartsch, 1947), USNM 417444. E, I. Shell in frontal view. F, H. Shell in lateral view. G. Detail of apical whorls. Scale bars: A–C, E–F, H–I. 1 mm; D, G. 200 μm. Credits: C–D. USNM

FIGURE 20. A–C. Aclis conula Dall, 1927. Holotype, USNM 108022. A. Shell in frontal view. B. Shell in dorsal view. C. Protoconch in apical view; arrow indicate transition protoconch-teleoconch. D–F. Aclis pyramida Dall, 1927: Holotype, USNM 108223. D. Shell in frontal view. E. Shell in lateral view. F. Protoconch in apical view; arrow indicate transition protoconchteleoconch. Scale bars: A–B, D–E. 1 mm; C, F. 200 μm. Credits: USNM.