Leptochiton tavianii

Leptochiton tavianii ( Dell’Angelo, Landau & Marquet, 2004)

Fig. 24 View FIGURE 24

Lepidopleurus ( Leptochiton) tavianii Dell’Angelo, Landau & Marquet, 2004, p. 29, pl. 1, figs 1–8, pl. 2, figs 1, 5; Dell’Angelo & Bonfitto 2005, p. 5, figs 9–12; Schwabe 2005, p. 103.

Leptochiton tavianii ; Dell’Angelo et al. 2013, p. 71, 76; Bertolaso et al. 2015, p. 9: Dell’Angelo et al. 2015a, p. 228.

Type material. Holotype: MZB 25049 (1 intermediate valve, Figs 24A–C View FIGURE 24 ). Paratypes: MZB 25050 (1 intermediate and 1 tail valve); MME (1 intermediate and 1 tail valve); IRScN IST 6449 (1 intermediate and 1 tail valve); BD 4566 (2 intermediate valves, Fig. 24I View FIGURE 24 ); RM (2 intermediate valves) .

Type locality. Estepona , Velerín Carretera ( Spain) .

Type stage. Pliocene , lower Piacenzian .

Material examined. Pliocene: Spain: Estepona : type material plus 38 valves ( BD 400 , Figs 24D–H, 24J–L View FIGURE 24 ). Maximum width of the valves: 3.7 / 4.6 / 3.5 mm .

Description. Head valve semicircular, posterior margin widely V-shaped, slope straight. Intermediate valves broadly rectangular (W/L 2.27–2.54), rounded in anterior profile, elevated (H/W = 0.39–0.55), anterior margin slightly convex, side margins rounded, posterior margin straight, apex inconspicuous, lateral areas slightly or not raised. Tail valve more than semicircular (W/L = 1.57–1.83), anterior margin almost straight, mucro subcentral, prominent, antemucronal slope straight, postmucronal slope concave.

Tegmentum rough, uniformly sculptured with well raised, neatly separated, fungiform section granules (width 54–65 μm), arranged in bee’s nest structure, i.e. six granules at corners of hexagon and one in the center, suggesting longitudinal or radial, mutually staggered striae, or a trellis-work structure, of diagonal, intersect striae. Each granule with generally 5 aesthetes of equal width, one of which lies in axial plane of prominence with the other four situated two by two at its sides.

Articulamentum without insertion laminae, apophyses small, sharply triangular, widely separated by large jugal sinus, apical area expanded, with bisinuate superior margin.

Remarks. The fossil record of Leptochiton tavianii ( Dell’Angelo, Landau & Marquet, 2004) is limited to the Pliocene of Estepona ( Spain). The head valve was not known in the material described by Dell’Angelo et al. (2004), and it is here figured ( Figs 24D–E View FIGURE 24 ).

Comparisons. Leptochiton tavianii is well characterized by the sculpture of tegmentum which differs from closer species in the L. tavianii group spp. by the granules with fungiform section arranged in beehive structure.

Distribution. Pliocene: western Mediterranean, Estepona Basin, Spain: Estepona (Dell’Angelo et al. 2004; this paper).