Ischnochiton rissoi ( Payraudeau, 1826 )

Ischnochiton rissoi ( Payraudeau, 1826) View in CoL

Fig. 60 View FIGURE 60

Chiton rissoi Payraudeau, 1826, p. 87 , pl. 3, figs 4–5; Seguenza 1874, p. 12; Seguenza 1876, p. 264; Seguenza 1883, p. 90; Scalia 1900, p. 16; Scalia 1907, p. 29; Francaviglia 1940, p. 65.

Ischnochiton rudolticensis Šulc, 1934, p. 23 , pl. 2, figs 41–43; Ashby & Cotton 1935, p. 392; Fischer P.-H. 1957 (cf.), p. 17; Bałuk 1971, p. 458, pl. 3, figs 5–8; Van Belle & Dell’Angelo 1998, p. 78.

Ischnochiton rissoi View in CoL ; Nierstrasz 1906, p. 163, figs 10, 12; Francaviglia 1960, p. 637; Malatesta 1962, p. 160, figs 16–17; Moroni 1967, p. 143; Ruggieri & Milone 1973, p. 221; Ruggieri & Unti 1978, p. 50; Sabelli & Taviani 1979, p. 161, pl. 1, figs 17–19; Di Geronimo 1979a, p. 47; Giammarinaro & Gucciardo 1981, p. 38; Bałuk 1984, p. 287, pl. 6, figs 2a–b; Laghi 1977, p. 556; Sabelli & Taviani 1984, p. 269; Bertarelli & Inzani 1985, p. 299; Crovato & Taviani 1985, p. 292; Studencka & Studencki 1988: tab. 2; Kaas & Van Belle 1990, p. 78, fig. 32; Cavallo & Repetto 1992, p. 30, fig. 1; Tabanelli & Segurini 1994, p. 7; Bellomo & Sabelli 1995, p. 201; Dell’Angelo & Forli 1995a, p. 230, fig. 15; Giani 1998, p. 115, pl. 43, fig. 1; Carmona Zalvide & García 1999, p. 178, figs 2–8; Dell’Angelo & Smriglio 1999, p. 100, pls 29–31, figs 40–48; Forli et al. 1999, p. 111; Dell’Angelo et al. 2001a, p. 150, figs 20, 23; Kroh 2002, p. 10; Kroh 2003, p. 132, pl. 1, fig. 5; Forli et al. 2003, p. 152; Chirli 2004, p. 6, pl. 2, figs 3–9; Dell’Angelo et al. 2004, p. 34, pl. 4, figs 3–4; Dulai 2005, p. 33, pl. 3, figs 1–5; Garilli et al. 2005, p. 132, pl. 2, figs 5–6; Dell’Angelo et al. 2007a, p. 41, fig. 4b; Puchalski et al. 2008, database chiton fossil records; Koskeridou et al. 2009, p. 314, figs 8.1–8.2; Sosso & Dell’Angelo 2010, p. 14, unnumbered fig. p. 16; Studencka & Dulai 2010, p. 264, text-fig. 4A–C; Dell’Angelo et al. 2012, p. 57, figs 3G, 3H; Dell’Angelo et al. 2013, p. 76, pl. 3, figs G–K; Dell’Angelo et al. 2015a, p. 232, pl. 4, figs 15–17; Ruman & Hudácková 2015, p. 166; Dell’Angelo et al. 2016, p. 96; Dell’Angelo et al. 2018b, p. 26, fig. 13; Dell’Angelo et al. 2020b, p. 52, tab. 9; Dell’Angelo et al. 2021b, p. 412, figs 46–53; Dulai & Katona 2024, p. 37, figs 10–18; Dulai 2025b, p. 27, figs 8–13.

Ischnochiton ( Simplischnochiton) rissoi View in CoL ; Laghi 1977, p. 104, pl. 1, figs 4–9; Mancini 1998, p. 29, pl. 1, unnumbered fig.; Dell’Angelo et al. 1999, p. 265, pl. 3, figs 3, 5; Mancini 1999, p. 20.

Ischnochiton cf. rissoi View in CoL ; Dulai 2025a, p. 7, figs 12–13.

Ischnochiton cf. korytnicensis View in CoL (non Ischnochiton korytnicensis Bałuk, 1971 View in CoL ); Studencka & Studencki 1988, p. 45 (= I. rissoi View in CoL , fide Studencka & Dulai 2010: 265).

non Ischnochiton rissoi View in CoL ; Dell’Angelo et al. 2018a, p. 22, figs 5A–I (= I. lesporti sp. nov., fide this study).

non Ischnochiton rudolticensis ; Bałuk 1965, p. 369, pl. 1, fig. 7 (= I. korytnicensis View in CoL , fide Bałuk 1971: 458).

Type material. Syntype MNHN 6109 .

Type locality. Bonifacio ( Corse, France) .

Material examined. Middle Miocene: Central Paratethys: Austria: Grund: 1 valve ( NHMW 1868/0001/0281), Pötzleinsdorf: 18 valves ( NHMW 1859/0027/0062, Figs 60S–T View FIGURE 60 , 1859/0038/0190, 2010/0256/0007); Romania: Kostej: 2 valves ( BD 466, NHMW 2010/0256/0003), Lapugy: 3 valves ( BD 467); Hungary: Bánd: 3 valves ( BD 468), Letkés: 4 valves ( BD 469); Eastern Paratethys: Ukraine: Horodok: 3 valves ( BD 470), Varovtsi: 133 valves ( BD 471, Figs 60M–R View FIGURE 60 ). Upper Miocene (Tortonian): France: Saint-Clément-de-la-Place: 7 valves ( MNHN.F.A67094, RGM.1008373, Figs 60K–L View FIGURE 60 , RGM.1008374, BD 140). Italy: Borelli: 1 valve ( MGPT PU 135040), Montegibbio: 4 valves ( BD 472, MZB 32019), Rio di Bocca d’Asino: 12 valves ( BD 473, PG, MZB 32018, MZB 32020, Figs 60E–F View FIGURE 60 ), Villa Monti: 2 valves ( BD 474, MZB 32049). Lower Pliocene: Italy: Liguria: Borzoli: 7 valves ( BD 475), Bussana: 4 valves ( BD 476, PG, MZB 45707, MZB 45709), Garlenda: 1 valve ( MP), Rio Sant’Antonino: 26 valves ( BD 477, MP), Rio Torsero: 6 valves ( BD 478, PG, SR, MZB 45708). Pliocene: Spain: Estepona: 13 valves ( BD 479). Italy: Emilia-Romagna: Gagliardella “Tagliata”: 2 valves ( BD 480), Marzeno: 1 valve ( BD 481), Rio Merli: 1 valve ( BD 482); Tuscany: Bibbiano: 1 valve ( BD 483), Castell’Anselmo: 1 valve ( BD 484), Castelnuovo Berardenga: 1 valve ( BD 485), Cetona: 1 valve ( BD 486), Colle Val d’Elsa: 3 valves ( BD 487), Montenero: 1 valve ( BD 488), Orciano Pisano: 3 valves ( BD 489), Pietrafitta: 46 valves ( BD 490), Pietrafitta Melograni: 17 valves ( BD 491), Serre di Rapolano: 29 valves ( BD 492, Figs 60B–D View FIGURE 60 ); Latium: Magliano Sabina: 7 valves ( BD 493); Sicily: Altavilla: 3 valves ( AG, AR, BD 494), Sciacca: 2 valves ( BD 495), Trappeto: 6 valves ( BD 496). Pleistocene: Italy: Emilia-Romagna: Torrente Stirone: 4 valves ( BD 497); Tuscany: Cisternino: 2 valves ( BD 498), Fauglia: 11 valves ( BD 499), Riparbella: 3 valves ( BD 500); Puglia: Gallipoli: 4 valves ( BD 501), Marina di Novaglie : 1 valve ( BD 502); Calabria: Archi S. Francesco: 50 valves ( BD 503, Figs 60A, 60G–J View FIGURE 60 ), Carrabbati: 1 valve ( BD 504), Castellace: 1 valve ( BD 505), Le Castella: 2 valves ( BD 506), Musalà: 5 valves ( BD 507), Pecoraro: 8 valves ( BD 508), Pezzo: 7 valves ( BD 509), Saracinello: 4 valves ( BD 510), Stalettì: 7 valves ( BD 511), Terreti: 1 valve ( BD 512), Valle Lamato: 1 valve ( BD 513); Sicily: Capo Milazzo: 4 valves ( BD 514), Grammichele: 1 valve ( BD 515), Melilli: 1 valve ( BD 516), Menfi: 2 valves ( BD 517). Greece: Kyllini: 5 valves ( BD 518, DGUP). Maximum width of the valves: 7.5 / 10 / 6.3 mm.

Description. Head valve semicircular, posterior margin widely V-shaped. Intermediate valves broadly rectangular (W/L = 2.25–3.12), moderately to highly elevated (H/W = 0.38–0.50), regularly rounded in anterior profile, anterior margin almost straight on jugal side, side margins slightly rounded, posterior margin straight, without trace of apex, lateral areas moderately elevated. Tail valve semicircular (W/L = 1.39–1.74), mucro centrally swollen but not prominent, antemucronal slope almost straight to slightly convex, postmucronal slope slightly concave just under mucro.

Tegmental sculpture varies from obsolete to quite strongly marked. HV, LA and PA sculptured with concentric vermicular ribs, often intersected by fine radial furrows, which give an aspect of granulose radial ribs; CA and AA sculptured with quite regular longitudinal ribs, more spaced near lateral margins, thinner and closer together in jugal area. Tegmentum fully covered by aesthetes, both on nodular elevations (without a clearly recognizable structure of megalaesthetes and micraesthetes) and between them.

Articulamentum with apophyses rounded, trapezoidal in tail valve, jugal sinus wide, about a third of valve’s width, insertion lamina divided into rather large, irregular teeth, slit formula: 10–13 / 1 / 9–12.

Remarks. Ischnochiton rissoi ( Payraudeau, 1826) is rather common in the Mediterranean Sea, very variable in size, sculpture and colour, and this morphological variability has produced taxonomic discrepancies, with the description of numerous species or varieties, now considered as synonyms, e.g., Chiton mediterraneus Reeve, 1847 , Chiton meneghinii Capellini, 1859 , Lepidopleurus meneghinii var. dautzenbergi Ancey, 1898 ( Kaas & Van Belle 1990; Dell’Angelo & Smriglio 1999; Carmona Zalvide & García 1999). Based upon only shell’s morphological features, the variability observed in I. rissoi mainly concerns the tegmentum sculpture in HV, LA and PA, with more or less regular radial ribs sometimes interrupted by concentric ribs, or with the vermicular ribs in LA tending to become longitudinal and parallel ribs in CA ( Nierstrasz 1906: fig. 13; Carmona Zalvide & García 1999, figs 2–5).

In the paleontological record, valves attributable to Ischnochiton rissoi are generally uncommon, with greater frequency of valves with a radial ribbing sculpture stronger than concentric ribbing on HV, LA and PA ( Figs 60D–F, 60K, 60M–N, 60Q, 60S View FIGURE 60 ); also the other types of sculpture are present, namely shells with radial ribs that intersect the concentric ribs showing a more granular structure ( Figs 60C, 60G View FIGURE 60 ) and concentric vermicular ribs ( Figs 60A–B, 60J View FIGURE 60 )

Already Šulc (1934) mentioned the similarity between I. rudolticensis Šulc, 1934 and 1. rissoi and later Laghi (1977) placed Šulc’s species into the synonymy of I. rissoi . In some earlier papers Malatesta (1962) and Bałuk (1971) supposed that I. rudolticensis is the Miocene ancestor of the Recent I. rissoi . The conspecificity of I. rudolticensis and 1. rissoi was confirmed by several authors ( Bałuk 1984; Dulai 2005, Dell’Angelo et al. 2007a; Studencka & Dulai 2010) and we agree and illustrate some material from the Paratethys ( Figs 60M–T View FIGURE 60 ).

The valves examined show a high degree of variability in shape and sculpture, both in intermediate valves (W/L = 2.25–3.12, while the profile is always rounded, H/W = 0.38–0.50) and in tail ones (W/L = 1.39–1.74). Also the number of longitudinal ribs in CA and AMA is variable, the ribs are quite regular and parallel, sometimes slightly slanting towards the side margins, splitting more frequently near the anterior margin.

Comparisons. The species is similar to Ischnochiton lesporti sp. nov. and I. sigwartae sp. nov.

Distribution. Middle Miocene: Central Paratethys (Langhian–Serravallian): Austria: Gainfarn, Grund, Pötzleinsdorf ( Kroh 2002, 2003; this study), Czech Republic: Kninice, Rudoltice ( Šulc 1934), Hungary: Bánd, Devecser, Letkés, Várpalota ( Dulai 2005, 2025 a, 2025b; Dulai & Katona 2024; this study), Poland: Korytnica ( Bałuk 1971, 1984), Romania: Kostej, Lapugiu ( Dell’Angelo et al. 2007a; this study); Eastern Paratethys: Ukraine: Horodok, Varovtsi ( Studencka & Dulai 2010; this study). Upper Miocene: northeastern Atlantic (Tortonian): Ligerian Basin, France: Saint-Clément-de-la-Place ( Dell’Angelo et al. 2018b); Proto–Mediterranean Sea (Tortonian and Messinian): Po Basin, N Italy: Borelli, Montegibbio, Rio di Bocca d’Asino, Villa Monti (Dell’Angelo et al. 1999, 2015a). Lower Pliocene: central Mediterranean, Italy: Liguria: Borzoli, Bussana, Garlenda, Rio S. Antonino, Rio Torsero ( Sosso & Dell’Angelo 2010; Dell’Angelo et al. 2013, 2021b). Pliocene: western Mediterranean, Estepona Basin, Spain: Estepona (Dell’Angelo et al. 2004); central Mediterranean, Italy: many localities in Tuscany, Emilia-Romagna, Latium and Sicily ( Laghi 1977; Dell’Angelo et al. 2001a, 2012; Chirli 2004; this study). Upper Pliocene to upper Pleistocene: central Mediterranean, Greece: Rhodes ( Koskeridou et al. 2009). Pleistocene: central Mediterranean, Italy: many localities in Tuscany, Emilia-Romagna, Puglia, Calabria, Sicily ( Sabelli & Taviani 1979; Dell’Angelo et al. 2001a; this study). Middle to upper Pleistocene: central Mediterranean, Greece ( Garilli et al. 2005), Italy (this study). Recent: Atlantic coasts, from Spain and Portugal ( Consolado Macedo et al. 1999; Urgorri et al. 2017) south to Morocco ( Pallary 1920), Canary Islands ( Kaas 1991; Rolan 2011) and Berlengas Archipelago ( Pisani Burnay 1986).Mediterranean Sea: France (B.D.D. 1882); Italy ( Dell’Angelo & Smriglio 1999), Croatia ( Dell’Angelo & Zavodnik 2004), Rhodes, Cyprus, Aegean Sea ( Zenetos & Van Aartsen 1995; Koukouras & Karachle 2005), Turkey ( Ozturk et al. 2014), Israel ( Barash & Danin 1977; Barash 1982), Tunisia: Gulf of Gabes ( Cecalupo et al. 2008).