Jujubinus fraterculus Monterosato, 1880

SSH XIII – Fig. 7P–R

Jujubinus fraterculus Monterosato, 1880: 220 (no figure).

Diagnosis

Shell of large size for the genus, not very solid, 4–5 elevated, flat, equidistant spiral cords, interspaces with fine prosocline lamellae, peripheral cord very evident, high height/width ratio.

Type material

Syntypes TUNISIA • 8 dd; Sfax; “ Monotrochus fraterculus Monts Spugne di Sfax!”; MCZR-M-11705/S • 26 dd; Sfax; “ M. fraterculus Monts (Zyziph.), Boll. Malacologico Italiano 1880 p. 220 spugne di Sfax ” MCZR- M-11705/S • 2 dd; Gulf of Gabès; “Golfo di Gabes ”; MCZR-M-11705/S • 6 dd; “ Sfax ”; MCZR-M-11705/S • 13 dd; Mediterranean coasts of Northern Africa [unprecised locality]; “Africa”; MCZR-M-11758/S • 8 dd; Mediterranean coasts of Northern Africa [unprecised locality]; labelled “ C. d’Afr. ” (Appolloni et al. 2018); MCZR-M-11758/S.

Other material examined

TUNISIA • 1 dd; Sfax; “smaragd. vr. Altior Mts Sfax, spugne”; MCZR-M-11761 • 34 dd; N of Zarzis; 33°36′28″ N, 11°04′04″ E; 0–7 m depth; MO • 3 dd; Djerba I.; 0.5 m depth; lagoon bioclastic sediment; LT • 1 dd; Djerba I.; beached; MO • 3 sh; Kerkennah; beached; MO • 4 dd; Kerkennah, Borj El Hsar Is.; beached; CS-PM • 150 dd; Kerkennah, Sidi Yousef; beached; CS-PM • 4 dd; Kerkennah, West of Gharbi I., Sidi Youssef; 0.5 m depth; LT • 2 lv; Kerkennah, Gharbi I., Sidi Youssef; 34°45′50″ N, 11°19′55″ E; 0–1 m depth; used for DNA sequencing; BAU 2314.1 – 2 • 1 lv; Kerkennah, Chergui I.; 34°43′21″ N, 11°09′21″ E; 0–2 m depth; used for DNA sequencing; BAU 2311.1 • 1 lv; Kerkennah, Chergui I.; 34°43′21″ N, 11°09′21″ E; 0–2 m depth; used for DNA sequencing; BAU 2312.1 • 4 dd; unprecised locality; “ Jujubinus sp. C. di Barberia”; MCZR-M-11762.

Description

SHELL. Shell of large size for the genus, height 10.0–11.0 mm, width 7.5–8.0 mm, height/width ratio 1.34– 1.38 conical, light. Protoconch seemingly smooth, of ca 0.8 whorls, 0.25–0.26 mm in width. Teleoconch of 5.5–6.5 slightly convex whorls. Sculpture of 4–5 flat, closely set abapical spiral cords of about the same strength, including the 2 peripheral ones forming the peripheral cord, slightly shouldered, and 6–7 regularly spaced, basal spiral cords large and flat. Spiral interspaces with thick and strong prosocline lamellae regularly set. Suture incised. Base convex, umbilicus closed also in juveniles, covered with a white callus. Aperture quadrangular, with the columellar callus thickened in the middle portion. Interior of the aperture whitish, nacreous.

COLOURATION. Colour of protoconch and initial teleoconch whorls whitish or greyish; remaining whorls and base cream or brownish with alternating notches of colour brownish-reddish

SOFT PARTS. Observed in alcohol preserved specimens, no dark terminal strip is present on the creamy band of the snout.

Distribution

Kerkennah Islands (Gulf of Gabès, Tunisia), as a variety of J. unidentatus (Ghisotti & Melone 1975). Specimens reported under this name by Scuderi & Terlizzi (2012) from Apulia belong to another species. Currently J. fraterculus is known only from the Gulf of Gabès, Tunisia, and it can be considered endemic to that area; living specimens at depths of 0– 2 m.

Remarks

Jujubinus fraterculus differs from J. exasperatus, J. pseudogravinae, J. gravinae and J. dianiensis sp. nov. in the complete or partial absence of tubercles on the spiral cords; from J. vexationis (Madeira), J. swinneni sp. nov. (Canary Islands) and J. ruscurianus (western Mediterranean), in the more slender outline and stronger sculpture (with marked striae in the spiral interspaces in J. fraterculus vs thin prosocline striae in J. swinneni and J. ruscurianus); from J. superum sp. nov. and J. vulgaris in its stouter outline, and more marked sculpture; from J. elenchoides in its smaller size, and the fewer and slightly more marked spiral cords; from J. kyrnos sp. nov., in its more slender shape and more marked prosocline lamellae in the interspaces; from J. depictus) in its more slender outline (vs a more cyrtoconoid one in J. depictus) and in the colouration (whitish or greyish or brownish in J. fraterculus vs wine reddish, reddish brown or whitish-reddish background with white blotches in J. depictus); from J. sartorii in its smaller size with narrower base and more angled periphery, and in the colouration (whitish or greyish or brownish of J. fraterculus vs bright whitish-pinkish J. sartorii). See under J. gofasi sp. nov., J. dianiensis, J. striatus, J. smaragdinus, J. inopinatus sp. nov., J. angustibasis sp. nov., J. dispar, for comparative remarks.