Lepidochitona monterosatoi Kaas & Van Belle, 1981

Lepidochitona monterosatoi Kaas & Van Belle, 1981 View in CoL

Fig. 104 View FIGURE 104

Lepidochitona ( L.) monterosatoi Kaas & Van Belle, 1981, p. 23 View in CoL , figs 7–9.

Lepidochitona monterosatoi View in CoL ; Kaas & Van Belle 1985b, p. 99, fig. 46; Strack 1993, p. 8, pl. 2, fig. 9; Dell’Angelo & Forli 1995a, p. 229, fig. 7; Giani 1998, p. 115; Dell’Angelo & Smriglio 1999, p. 158, pls 52–53, figs 79–83; Forli et al. 1999, p. 111, pl. 1, fig. 8; Dell’Angelo et al. 2001a, p. 148, fig. 14; Chirli 2004, p. 11, pl. 3, figs 10–11; Dell’Angelo et al. 2004, p. 39; Puchalski et al. 2008 (database: chiton fossil records); Koskeridou et al. 2009, p. 320, figs 10.8–10.10; Sosso & Dell’Angelo 2010, p. 15, fig. p. 17; Dell’Angelo et al. 2013, p. 92, pl. 9, figs A–F; Dell’Angelo et al. 2016, p. 83, pl. 4, figs 6–10 (non figs 4–5, = Lepidochitona sp. ); Dell’Angelo et al. 2020b, p. 53, tab 9; Dell’Angelo et al. 2021b, p. 425, figs 146–149.

non Lepidochitona monterosatoi View in CoL ; Macioszczyk 1988, p. 52, pl. 2, figs 6–8 (= L. lepida , see below).

Type material. Holotype: RMNH 55386 About RMNH /1; one specimen, length 7.8 mm . Paratypes: VB 2587a/1: one specimen disarticulated from Toulon, Le Carnier ( France) ; VB 2587b/1: one specimen from Torba ( Turkey) ; K 4849/1; one specimen from Torba ( Turkey) ; MNHN/1: one specimen from Torba ( Turkey) ; IRSN 26095 View Materials /1: one specimen from Tuscan Archipelago ( Italy) .

Type locality. Cap d’Antibes, Port de l’Olivette ( France), on a stone on sandy bottom, 0.5 m .

Material examined. Upper Miocene: Italy: Montegibbio: 7 valves ( BD 895, MZB 32096), Rio di Bocca d’Asino: 16 valves ( BD 894, MZB 32094–32095, Figs 104C–D View FIGURE 104 , PG). Lower Pliocene: Italy: Liguria: Borzoli: 4 valves ( BD); Bussana: 9 valves ( BD 896); Caranchi: 1 valve ( MZB 45758); Rio Sant’Antonino: 15 valves ( BD 897, Figs 104A–B View FIGURE 104 , MP, MZB 45759–45760, Figs 104K–L View FIGURE 104 ). Pliocene: Italy: Tuscany: Colle Val d’Elsa: 6 valves ( BD 898), Montenero: 2 valves ( BD 899), Orciano Pisano: 6 valves ( BD 900), Pietrafitta Melograni: 1 valve ( BD 901), Poggio alla Fame: 5 valves ( BD 902, Figs 104H–J View FIGURE 104 ). Pleistocene: Italy: Tuscany: Cisternino: 5 valves ( BD 903), Riparbella: 5 valves ( BD 904); Calabria: Le Castella: 3 valves ( BD 905), Pecoraro: 2 valves ( BD 906), Torrente Boscaino: 1 valve ( BD 907); Sicily: Capo Milazzo: 2 valves ( BD 908). Recent: Ustica Island: valves ( BD 909, Figs 104E–G View FIGURE 104 ). Maximum width of the valves: 2 / 2.5 / 2 mm.

Description. Head valve semicircular, with 8 radial depressions crossing its surface, posterior margin forms a very obtuse angle. Intermediate valves broadly rectangular (W/L = 2.04–2.27), moderately elevated (H/W = 0.53–0.57), semicarinate in anterior profile, anterior margin slightly concave between the apophyses, side margins rounded, posterior margin with strongly protruded apex, lateral areas conspicuously raised. Tail valve elliptical (W/ L = 1.92), anterior margin slightly convex, mucro subcentral, not prominent, antemucronal slope almost straight, postmucronal slope slightly concave.

Tegmentum rather coarsely granulated, granules roundish/oval (diameter up to 60–75 µm), convex, arranged in quincunx on HV, LA and PMA, and also on JA; arranged in curved and diverging longitudinal series on PA and AMA. Each granule with a central megalaesthete, and several micraesthetes (up to 15–20) irregularly arranged along margin, also in depressions between granules.

Articulamentum with apophyses broadly triangular in intermediate valves, trapezoid in tail valve, separate by a jugal sinus about one third of the valve’s width, teeth obtuse, rugose on outside, slit formula 8 / 1 / 11, slits short, inequidistant, slit rays clearly visible, eaves spongy.

Remarks. The species is rather rare as a fossil, with scarce records from the Italian Miocene, whilsts is commoner in the Plio-Pleistocene. Complete valves are rare, many of the examined valves are small fragments, in poor conditions of preservation, which makes specific attribution more difficult.

Dell’Angelo et al. (2016) attributed tentatively to Lepidochitona monterosatoi Kaas & Van Belle, 1981 two incomplete valves (head and intermediate) from the Middle Miocene (Serravallian) of Monchio di Sarzano Casina (Italy) . Despite the existing similarity with L. monterosatoi , it is not possible to identify with certainty these valves, that are discussed and figured in the section dedicated to the “species of problematic assignment”, and are left in open nomenclature as Lepidochitona sp.

The original description of this species by Kaas & Van Belle reports H/W = 0.41, while the fossil material examined shows a higher value, from 0.53 to 0.57. On the other hand, also the living intermediate valves from Favignana Island ( Dell’Angelo & Smriglio 1999: pl. 53, fig. I) and from Ustica Island ( Figs 104E–G View FIGURE 104 ) shows H/W values within the range of variation of fossil valves.

The living specimens recorded from the Red Sea (Dahlak islands) by Leloup (1980), as Middendorffia caprearum ( Scacchi, 1836) , were later ascribed to L. monterosatoi by Strack (1993). The validity of this unique record outside the typical range needs to be reconsidered.

Comparisons. Lepidochitona monterosatoi Kaas & Van Belle, 1981 is easily distinguishable from the other Mediterranean Lepidochitona by the intermediate valves highly elevated, the conspicuously raised lateral areas, and the arrangement of the granules on the pleural parts of the intermediate valves.

Distribution. Upper Miocene: Proto-Mediterranean Sea (Tortonian): Po Basin, N Italy: Montegibbio, Rio di Bocca d’Asino ( Dell’Angelo et al. 2016). Lower Pliocene: central Mediterranean, Italy: Liguria: Borzoli, Bussana, Caranchi, Rio S. Antonino ( Dell’Angelo et al. 2001a, 2013, 2021b). Pliocene: central Mediterranean, Italy: Tuscany: Colle Val d’Elsa, Montenero, Orciano Pisano, Pietrafitta Melograni, Poggio alla Fame ( Forli et al. 1999; Dell’Angelo et al. 2001a, 2013; Chirli 2004; this study). Upper Pliocene to upper Pleistocene: central Mediterranean, Greece: Rhodes Island ( Koskeridou et al. 2009). Pleistocene: central Mediterranean, Italy: Tuscany: Cisternino, Riparbella ( Dell’Angelo & Forli 1995a; this study), Calabria: Le Castella, Pecoraro, Torrente Boscaino (this study), Sicily: Capo Milazzo (this study). Recent: Atlantic Ocean: Spain and Portugal (Carmona Zalvide et al. 2000; Urgorri et al. 2017). Mediterranean Sea ( Dell’Angelo & Smriglio 1999; Koukouras & Karachle 2005; Cecalupo et al. 2008; Crocetta et al. 2014).