Mitromorpha (Mitrolumna) tricolorata, Amati, Bruno, Smriglio, Carlo & Oliverio, Marco, 2015

Mitromorpha (Mitrolumna) tricolorata n. sp.

( Figs 17 View FIGURE 17 ; 26 A–F; 27 O; 28 L)

Type material. Holotype Cala Calandra, Lampedusa Is., Central Mediterranean Sea, 30 m depth, 30.iv. 1991 (H. 5.65 mm, W 2.9 mm), ( MNHN IM- 2000-27713) ( Fig. 26 View FIGURE 26 A–C; 28 L). Paratypes: type locality, 2 sh + 6 juv. (INC); 2 sh (BA); Capo Grecale, Lampedusa Is., 50 m, vii.2009, 2 sh (BA), 1 sh (CS), 1 sh (MO).

Type locality. Cala Calandra, Lampedusa Is., Central Mediterranean Sea, 30 m depth.

Other material examined. Italy: Capo Grecale, Lampedusa Is., 50 m, vii.2009, 2 sh (BA); type locality, 4 sh juv. (BA), 1 sh juv. (MO); Lampedusa Is., Punta Cappellone, Sicily, 4 sh (PC).

Etymology. After the chromatic pattern of the shell, with caramel, violet and white colors.

Distribution and habitat. Known so far only from the type locality, Lampedusa Is., Central Mediterranean Sea. Recent. Empty shells in bioclastic sands, from 30– 50 m. Found sympatric, often at different depths, with M. olivoidea , M. columbellaria and M. karpathoensis .

Description. (in parentheses the data of the holotype) Shell small for the genus ( Figs 26 View FIGURE 26 A–F; 27 O), height 5.6–6.15 (5.65 mm), width 2.75–2.95 (2.9 mm), solid, fusiform, biconic, slender, H/W= 1.931–2.084 (1.948); a single, particularly slender specimen (Cala Calandra, Lampedusa Is.) with a H/ W 2.218. Protoconch paucispiral ( Fig. 28 L View FIGURE 28. A – L ) shiny, slender, of 1.3–1.4 (1.4) convex whorl, d 0.20–0.225 (0.20 mm), Do 0.35–0.375 (0.35mm), DM 0.45–0.50 (0.50 mm), h 0.45 mm (0.45 mm), covered by large, densely arranged, subtriangular granules. Protoconch-teleoconch boundary well marked, slightly flexuose, opisthocline. Teleoconch of 4.4–5 (4.5) slightly convex whorls. Sculpture starting with 3–4 (3) spiral cordlets crossed by 13 (13) axial ribs on the first whorl, the abapical spiral more pronounced in the first two whorls, giving the spire a keeled outline. Additional spiral cordlets between the adapical ones and between the suprasutural one and the suture. Last whorl sculptured over the entire surface by 18–22 (18) strong spiral cordlets, flat, equidistant, of equal size, of which 4 (4) above the aperture and one partly masked by the suture. Axial ribs not present on the last 0.9 whorl. Two columellar folds, the posterior larger. Growth lines visible over the entire surface. Outer lip sharp, thickened internally with 7 (7) denticles, the second or third posterior larger. Anal sinus shallow. Siphonal canal short, and wide. Coloration caramel in the background, with subsutural and basal areas lighter, a whitish stripe always present on the adapical spiral cordlet, more evident on the lasts whorl. Protoconch neatly lighter than the rest of the shell, first teleoconch whorls and aperture violet. Soft parts unknown.

Remarks. M. tricolorata n. sp. is characterised by a peculiar chromatic pattern, and by the constant presence of a prominent abapical spiral cordlet, which gives the first whorls a keeled appearance. M. karpathoensis ( Figs 11 View FIGURE 11 A–P; 16 A; 27 M) has fewer and larger nodules on the first whorls. M. columbellaria ( Figs 1–5 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 ; 27 A–E) has a different chromatic pattern, being almost monochrome, with rare specimens bearing a differently colored subsutural band and the first whorls not keeled. M. mariottinii n. sp. has fewer spirals on the last whorl (14– 18 v. 18–22 in M. tricolorata ), a different outline with almost flat spire and a more blunt apex. M. mifsudi n. sp. has broader spirals with finer interspaces, and more robust columellar folds.

Table 1. Ranges of morphometric characters of the teleoconch in Mediterranean species of the genus Mitromorpha . Measurements in mm.

(ad): sample size (full grown intact adults); H: height; W: width; H/W; ratio height/width; Nw: number of whorls; Nrfw: number axial ribs on the first whorl; Nrpw: number axial ribs on the penultimate whorl; Nslw(aa): number of spirals on the last whorl (above the aperture); Nd: number of denticles; Sts: starting number of spiral cordlets. H, W (and H/W), Nw, Nrpw, Nslw, Nsuw(aa), Nd have been measured/counted only on fully grown adults.

exceptionally upt to 8 (see text); ** occasionally lacking (see text); *** up to 9 in the deep-water morph

Table 2. Morphometric characters of the protoconch in Mediterranean species of the genus Mitromorpha . Measurements in mm. N: sample size; h = height; d = diameter nucleus ; Do= diameter of first half whorl; DM = maximum diameter; npw = number of protoconch whorls; Ptb =Protoconch-teleoconch boundary.