Granulina ronaldi, Elm & Hoffman, 2024

Elm, Laura-Marie Von & Hoffman, Leon, 2024, Revision of deep-water species in Granulina (Gastropoda: Granulinidae) from Mauritania and Western Sahara, European Journal of Taxonomy 925, pp. 268-291 : 280-282

Granulina ronaldi sp. nov.

urn:lsid:zoobank.org:act:38316ACE-B8E8-4743-8F4D-59785DA8AED2

Figs 5 , 7

Diagnosis

Small shell, height maximum 2.9 mm, width maximum 1.7 mm (width/height ratio 0.59), tumidity maximum 1.4 mm, ovoid-angular shape, rather narrow shape; no labial denticles on interior of external lip, tapered and weakly rostrated apically and abapically, widely channelled abapically, colour white, translucent.

Etymology

The name (masculine) of the species acknowledges Ronald Janssen, retired curator of the Mollusca collection in the Senckenberg Museum Frankfurt who salvaged the Meteor material when it was about to be discarded and who initiated the preservation and sorting process. He also allowed us to study the Meteor samples.

Type material

Holotype

MAURITANIA – Banc d’Arguin • 1 shell; 19.35° N, 16.9333° W; depth 200 m; 31 Oct. 1978; CANCAP stn 3.154; SMF359026 .

Paratypes (40 shells)

MAURITANIA – Banc d’Arguin • 3 shells; same collection data as for holotype; SMF 359020 , SMF 359027 , SMF 359029 • 25 shells; same collection data as for holotype; RMNH.MOL.351810 • 8 shells; 19.94° N, 17.48° W; depth 151 m; 22 May 1988; Tyro Mauritania I stn B5; box core; SMF 359028 • 4 shells; 18.9833° N, 16.8333° W; depth 203 m; 30 Oct. 1978; CANCAP stn 3.140; sandy clay with shells; van Veen grab; RMNH.MOL.351811 .

Other material examined (159 shells)

MAURITANIA – Banc d’Arguin • 12 shells; 20.3651° N, 17.6834° W; depth 246 m; 24 Oct. 2010; MSM16–3 stn GeoB14704; box core in muddy silt; SaM .

WESTERN SAHARA – off Cap Blanc • 6 shells; 21.325° N, 17.37° W; depth 81 m; 25 Feb. 1977; M44 stn 235–KG649; box core; SMF. – North of Dakhla • 2 shells; 25.3333° N, 16.1533° W; depth 411 m; 5 Feb. 1982; M60 stn 49–KG921, box core; SMF • 1 shell; 25.3333° N, 16.1533° W; depth 407 m; 5 Feb. 1982; M60 stn 43–KG922; box core; SMF • 10 shells; 25.1833° N, 15.8033° W; depth 87 m; 22 Feb. 1975; M36 stn 95–KG6; box core; SMF • 128 shells; 25.0000° N, 15.5167° W; depth 53 m; 21 Feb. 1975; M36 stn 94–KG2; box core; SMF .

Description

Apex with highly convex, blunt, narrowing channel. External lip smoothly rounded, strongly thickened from apex to base, maximum convexity slightly above periphery, reclining towards apex and base, widely channelled at highly convex base, pointed at base columella, internally smooth (without labial denticles). Four discrete oblique folds at base of straight columella, with round edges, third fold longest. Parietal area widely convex and smooth. Macroscopic sculpture smooth with microscopic irregular growth lines; microscopic sculpture of flakes oriented towards exterior on callus of external lip, columella, columellar folds, base and apex, callus reclining in the middle part; internally smooth. Aperture curved, elongated, wide at base. Protoconch invisible, convolved inside shell.

Remarks

Because of the missing labial denticles, this species cannot be mistaken for any hitherto known species found north of Senegal. The morphology is similar to Granulina occulta but that species has labial denticles. The outline of the present species is not as broad (width/height ratio 0.59) as in Granulina sandrae sp. nov. (width/height ratio 0.69) and it has a narrow aperture. Granulina reginae sp. nov. has a wide, notched apical channel and its last whorl is widely rounded at the periphery.

Granulina ronaldi sp. nov. could be mistaken for G. sigridae sp. nov. but that species has different columellar folds; the two upper ones are often coalescent and the third one is not as long as the fourth one. The micro-sculpture in the present species covers a wider area at the base of the callus and apex and is not as retracted in the parietal area as in G. sigridae either . The outer lip of the present species is more thickened, with weaker convexity and slightly angular. The (ab-) apical outlines are more convex than in G. sigridae .

La Perna et al. (2001) described the similar Granulina longa La Perna, Landau & Marquet, 2001 from the Pliocene near Estepona (western Mediterranean, Spain). Granulina longa differs from the present species by a well-rounded oval outline, a wide aperture and a thin lip with fine labial denticles. La Perna et al. (2003) described another similar species: Granulina choffati La Perna, Landau & da Silva, 2003 from the Atlantic Pliocene in Portugal. It is differentiated from the present species by fine labial denticulations, and a more oval outline.

The bathymetric range is 81– 411 m. The latitudinal range is 18.9– 25.4° N, which is the northernmost occurrence of the new species. Some shells were found in sandy or muddy silt occasionally with other shells. The habitat of the species is uncertain.

Figures

Fig. 5. Location map of the new species in Granulina Jousseaume, 1888 off Mauritania and Western Sahara. White circles show all investigated stations; colour symbols show locations of shells from new species. Granulina reginae sp. nov. is presented by yellow squares, G. sigridae sp. nov. as red diamonds, G. sandrae sp. nov. as blue triangles, and G. ronaldi sp. nov. as green circles. Bathymetric data from GEBCO; contours 500 m

Fig. 7. Granulina ronaldi sp. nov., Mauritania, off Banc d’Arguin, CANCAP/3.154. A–D. Holotype (SMF359026). A–B. Ventral and side views, height 2.9 mm, width 1.7 mm, tumidity 1.4 mm. C. Columellar folds. D. Micro-sculpture above second columellar fold, see arrow in C. E–F. Paratype (SMF359020), ventral and side views, height 2.5 mm, width 1.5 mm, tumidity 1.3 mm. G–H. Paratype (SMF359027), central and side views, height 2.5 mm, width 1.4 mm, tumidity 1.3 mm, callus line indicated by white dots. I–J. Paratype (SMF359029), ventral and side views, height 2.5 mm, width 1.5 mm, tumidity 1.2 mm.