Rhyssoplax phaseolina ( Monterosato, 1879 )

Rhyssoplax phaseolina ( Monterosato, 1879) View in CoL

Fig. 94 View FIGURE 94

Chiton rubicundus View in CoL O.G. Costa, 1829 var. phaseolinus Monterosato 1872, p. 29 View in CoL ; Monterosato 1875, p. 21 ( nomen nudum).

Chiton phaseolinus Monterosato, 1878a: 77 View in CoL ( nomen nudum).

Chiton phaseolinus Monterosato, 1879, p. 16 View in CoL ; Gaglini 1985, p. xv, pl. 5, fig. 3, pl. 13, fig. 5; Dell’Angelo & Forli, 1995a, p. 234; Appolloni et al. 2018, p. 22 View Cited Treatment , figs 1E–F.

Chiton ( Rhyssoplax) phaseolinus View in CoL ; Dell’Angelo & Smriglio 1999, p. 179, pls 60–61, figs 108–111; Kaas et al. 2006, p. 158, fig. 18, map 28.

Type material. MCZR –M–12674: 3 lots (1 spm from “Palermo Acqua Santa”; 1 spm from “ Golfo di Napoli ”; 2 spm and 5 valves from “Palermo Acqua Santa” ( Appolloni et al. 2018).

Type locality. Described from Palermo ( Sicily, Italy) and Gulf of Napoli ( Campania, Italy) .

Material examined. Pleistocene: Italy: Calabria: Gallina: 4 valves ( AV, Figs 94E–F View FIGURE 94 , BD 817); Sicily: Ustica: 1 valve ( MGUP 538, Figs 94C–D View FIGURE 94 ). Recent: Mediterranean Sea: Italy: Ognina ( BD 818), valves ( Figs 94A–B, 94G–H View FIGURE 94 ). Maximum width of the valves: -- / 2.9 / 2.8 mm.

Description. Head valve somewhat more than semicircular, posterior margin widely V-shaped, front slope weakly convex. Intermediate valves broadly rectangular (W/L = 2.43–2.66), moderately elevated (H/W = 0.40– 0.50), rounded to semicarinate in anterior profile, anterior margin about straight in a wide central part, roundly sloping at the sides, posterior margin straight to slightly concave at both sides of prominent, sharply pointed apex, lateral areas little raised, not separated from CA. Tail valve semicircular (W/L = 1.62), anterior margin weakly angularly convex, mucro at anterior third, rather prominent, antemucronal slope almost straight, postmucronal slope straight to slightly concave.

HV, LA and PMA smooth, concentric growth lines vaguely detectable. CA and AMA sculptured with 5–8 longitudinal folds on each side, of which only first two or three reach up to anterior margin, others cover a half or a third of length. Aesthetes very dense, each megalaesthete accompanied by many micraesthetes.

Articulamentum with apophyses wide, triangular with rounded top, connected across shallow sinus by short, finely denticulate jugal plate, insertion plates short, slit formula 8–14 / 1 / 8–9, slit rays hardly discernible, teeth rather blunt, finely grooved on the outside, eaves very narrow, finely porous.

Remarks. The fossil record of Rhyssoplax phaseolina ( Monterosato, 1879) known to date is limited to the Pleistocene of southern Italy; the valves here figured, from Ustica island ( Sicily) and Gallina (Apulia) represent the first record of this taxonl.

The species was formally described by Monterosato in 1879, although the taxon got mentioned in previous works: in 1872, as a variety of Chiton rubicundus O.G. Costa (“Var. = C. phaseolinus , mihi ms.”); in 1875, still as a variety of C. rubicundus ; and in 1878a.

Comparisons. Rhyssoplax phaseolina could be mistaken for R. corallina ( Risso, 1826) , from which it differs mainly by its smaller size, semicarinate profile of the intermediate valves, lateral areas little raised, not separated from the central area, and the mucro located more anteriorly. For the differences with Rhyssoplax etrusca see above.

Distribution. Pleistocene: central Mediterranean, S. Italy: Gallina, Ustica (this study). Recent: Atlantic Ocean: southwestern Spain: Cádiz (Carmona Zalvide et al. 2000). Mediterranean Sea: Spain (Capo de Gata, Algeciras), S. Italy ( Marina di Camerota , Sicily, Lampedusa, Pantelleria), Malta, Cyprus ( Dell’Angelo & Smriglio 1999; Kaas et al. 2006), Lebanon ( Crocetta et al. 2014).