Notopropebela petu, Sánchez & Damborenea & Pastorino, 2023

Sánchez, Noelia, Damborenea, Cristina & Pastorino, Guido, 2023, Unravelling the conoidean gastropods assigned to the genus Propebela (Gastropoda: Mangeliidae) from south-western Atlantic deep waters, Journal of Natural History 57 (1 - 4), pp. 243-256 : 249-251

Notopropebela petu sp. nov.

( Figure 3 (a–p), Table 4 )

urn:lsid:zoobank.org:act:D0130F68-6631-4368-91B1-5E68AF0B3C85

? Mangilia (sic) michaelseni – Castellanos 1970: pl. IX, fig. 12.

Mangelia michaelseni – Forcelli 2000: 110, fig. 326 (non Strebel, 1905)

Etymology. The specific name ′petu̍ refers to the name of the first author̍s dog, whose extremely fine hairs were utilised to clean radulae. Petu is used as a noun in apposition.

Type material. Holotype ( Figure 3 (a–c)) (MACN-In25516) and 2 paratypes: 1 ( Figure 3 (d–f)) (MACN-In25116) and 1 ( Figure 3 (g–h)) (MACN-In29655).

Type locality. 37°35 ʹ 3 ʹʹ S, 54°55 ʹ 3 ʹʹ W, off Buenos Aires Province, Argentina, at 210 m depth .

Examined material. Holotype and paratypes only.

Description. Shell ( Figure 3 (a–h)) small, up to 9.6 mm in maximum height, whitish in colour; spire half of the total shell height; protoconch ( Figure 3 (i–l)) high, paucispiral of ~1½ whorls, about 0.97 × 0.98 mm in height and width, respectively, with spirally arranged pustules ( Figure 3 (j)); protoconch-teleoconch boundary clearly defined; teleoconch of 3½ rounded whorls, all with pustules distributed over the entire surface (only visible under SEM) ( Figure 3 (m)); subsutural ramp wide and somewhat concave; suture moderately deep. Axial ornamentation of regularly spaced and pronounced thick riblets, 24 on 1st, 26 on 2nd and 3rd, increasing to 36 on last whorls. Spiral ornamentation of thick cords, 10 on 1st, 14 on 2nd, increasing to 35 on last whorls. Anal sinus deep and rounded on subsutural ramp. Columellar callus thickened. Siphonal canal moderately long. Aperture oval-elongate. Operculum absent. Radula ( Figure 3 (o)) of semi-enrolled marginal teeth, rachidian absent. Tooth ( Figure 3 (p)) ~120 μm long, with basal spur and ligament. Penis long ( Figure 3 (n)) (~ 1.2 mm for a shell height of 9 mm), with a semiconical tip. Cephalic tentacles short (~ 0.6 mm for a shell height of 9 mm), without visible eyes.

Distribution. Known only from type locality.

Remarks. Notopropebela petu sp. nov. has the longest spire of the genus with a conspicuous and somewhat concave subsutural ramp with a remarkable thickness below suture. In addition, the anal sinus is deeper and more rounded than in the other two species. Pustules cover the surface of the shell, and are only visible under SEM, as in N. pustulata sp. nov. The protoconch is larger and wider than the other two species of the genus (~0.97 × 0.98 mm, vs 0.6 × 0.9 mm in N. profunda and 0.6 × 0.7 mm in N. pustulata sp. nov.). Furthermore, the axial and spiral ornamentation form a distinctive cancellate grid as in N. pustulata sp. nov., which is thicker in N. petu sp. nov.

Castellanos (1970, p. 317, pl. 9, fig. 12) illustrates as Mangelia michaelseni ( Strebel, 1905) a shell that appears to be Notopropebela petu sp. nov. However, the lots cited under M. michaelseni in Castellanos̍s work, MACN-In25172 (in error 25772) and MACN-In17758 correspond to Falsimohnia sp. and to an undescribed species, respectively. In addition, Forcelli (2000) illustrates one specimen of N. petu sp. nov (figured here in Figure 3 (a–c)) as M. michaelseni , although he did not mention the specimen number.

Figures

Figure 3. Notopropebela petu sp. nov. (a–c) Holotype, MACN-In25516, 37.5841ʹS, 54.9175ʹW, off Buenos Aires Province, 210 m, three views of the shell. (d–f) Paratype, MACN-In25516, three views of the shell. (g–h) Paratype, MACN-In29655, 37.5841S, 54.9175ʹW, off Buenos Aires Province, 210 m, two views of the shell. (i–m) MACN-In29655; (i) lateral view of the protoconch; (j) detail of the same shell showing the pustules on the protoconch; (k) apical view of the protoconch; (l) other lateral view of the same protoconch; (m) detail of the same shell showing the pustules on the teleoconch. (n–p) MACN-In25516; (n) penis; (o) general view of the radula; (p) detail of the teeth. Scale bars: a– h = 5.0 mm; i, l = 500 µm; j, m, o = 50 µm; k, n = 200 µm; p = 20 µm.