Ischnochiton korytnicensis Bałuk, 1971

Ischnochiton korytnicensis Bałuk, 1971 View in CoL

Fig. 70 View FIGURE 70

Ischnochiton korytnicensis Bałuk, 1971, p. 458 View in CoL , pl. 3, figs 1 - 4; Bałuk & Radwanski 1979, p. 231; Van Belle 1981, p. 45; Bałuk

1984, p. 288, pl. 6, fig. 1a–b; Macioszczyk 1988, p. 52, pl. 2, fig. 9; Studencka & Studencki 1988, p. 43; Van Belle &

Dell’Angelo 1998, p. 78; Dulai 2005, p. 34; Dulai & Studencka 2007, p. 17; Studencka & Dulai 2010, p. 265; Dell’Angelo et al. 2013, p. 77, pl. 3, figs L–T; Dell’Angelo et al. 2015a, p. 234, pl. 5, figs 1–9; Ruman & Hudácková 2015, p. 166;

Dell’Angelo et al. 2016, p. 96; Dell’Angelo et al. 2018b, p. 53, tab. 17; Dell’Angelo et al. 2021b, p. 413, figs 54–61. Ischnochiton ( Simplischnochiton) korytnicensis ; Dell’Angelo et al. 1999, p. 267, pl. 3, figs 1–2. non Ischnochiton cf. korytnicensis ; Studencka & Studencki 1988, p. 45 (= I. rissoi , fide Studencka & Dulai 2010: 265). non Ischnochiton korytnicensis ; Dell’Angelo et al. 2018a, p. 23, figs 5J–L; Dell’Angelo et al. 2020b, p. 5, fig. 2 (= I. cluzaudi

sp. nov., fide this study) Ischnochiton rudolticensis (non Ischnochiton rudolticensis Šulc, 1934 ); Bałuk 1965, p. 369, pl. 1, fig. 7 ( fide Bałuk 1984). Ischnochiton rissoi (non Ischnochiton rissoi Payraudeau, 1826 ); Laghi 1977, p. 104, pl. 1, fig. 9 ( partim, non figs 4–8 = I.

rissoi).

Type material. Holotype in Bałuk’s collection, reg. No. BkK-A15, an intermediate valve illustrated in Bałuk (1971: pl. 3, fig. 2).

Type locality. Korytnica , southern slopes of the Holy Cross Mts. ( Poland) .

Type stage. Middle Miocene.

Material examined.Middle Miocene: Central Paratethys: Romania:Lapugy:1valve( NHMW2010 /0256/0005); Eastern Paratethys: Ukraine: Varovtsi : 21 valves ( BD 533 , Figs 70E–J View FIGURE 70 ). Miocene (Tortonian): Italy: Borelli : 9 valves ( PG, MZB 32026–32027 , MGPT PU 135041 ), Montegibbio: 21 valves ( BD 534 , MZB 32021–32022 , Figs 70C–D View FIGURE 70 ), Rio di Bocca d’Asino : 39 valves ( BD 535 , Figs 70K–L View FIGURE 70 , PG, MZB 32023–32025), Villa Monti: 3 valves ( BD 536 , MZB 32050 ) . Lower Pliocene : Italy: Liguria: Borzoli: 2 valves ( BD 537 , MZB 45712 ) ; Bussana : 15 valves ( BD 538 , PG, MZB 45714–45715 ) , Genova Sestri : 1 valve ( MZB 45710 ) , Rio Sant’Antonino : 3 valves ( MP) , Rio Torsero : 2 valves ( BD 539 , MZB 45711 , MZB 45713 ) . Pliocene : Italy: Piedmont: Vintebbio: 26 valves ( BD 540 , Figs 70A–B View FIGURE 70 ) ; Emilia-Romagna: Cava di Campore : 1 valve ( BD 541 ) . Maximum width of the valves: 8.3 / 9.5 / 7.2 mm .

Description. Head valve semicircular, posterior margin widely V-shaped. Intermediate valves broadly rectangular (W/L = 2.56–2.72), moderately elevated (H/W = 0.44), 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 = 1.50–1.79), anterior margin almost straight, mucro subcentral, antemucronal slope slightly convex, postmucronal slope slightly concave just under mucro.

HV, LA and PMA sculptured with closely spaced, elevated, irregularly distributed and irregularly shaped nodules, which in some cases, especially in PMA, give the impression to be arranged in radial rows. CA and AMA sculptured with quite regular longitudinal ribs, more spaced near lateral margins, more irregular in JA. 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, jugal sinus wide, insertion lamina divided into rather large, irregular teeth, slit formula: 11–12 / 1 / 12.

Remarks. This species was described from the Middle Miocene (Badenian) of Poland, and was subsequently found in several other deposits, from the Miocene to Pliocene, which extended its geographic and stratigraphic distribution outside the Paratethys.

Ischnochiton korytnicensis Bałuk, 1971 is similar to I. rissoi ( Payraudeau, 1826) , and the two species can coexist in the same sites, e.g., for the Miocene of Korytnica ( Bałuk 1971, 1984) and N. Italy ( Dell’Angelo et al. 2015a), and for the Pliocene of Liguria ( Dell’Angelo et al. 2013).

Comparisons. This species is similar to Ischnochiton rissoi ( Payraudeau, 1826) , from which it differs mainly in the ornamentation of HV, LA and PMA composed of irregular, closely spaced, and elevated nodules, whereas I. rissoi shows concentric vermicular or more or less radial ribs.

Distribution. Middle Miocene: Central Paratethys (Langhian-Serravallian): Poland: Korytnica, Łychów, Niskowa ( Bałuk 1965, 1971, 1984; Macioszczyk 1988), Romania: Lapugy (this study); Eastern Paratethys: Ukraine: Varovtsi (this study); Upper Miocene: Proto-Mediterranean Sea (Tortonian): Italy: Borelli, Montegibbio, Rio di Bocca d’Asino, Villa Monti ( Laghi, 1977; Dell’Angelo et al. 1999, 2015a). Lower Pliocene: central Mediterranean, Italy: Liguria: Borzoli, Bussana, Genova Sestri, Rio Sant’Antonino, Rio Torsero ( Sosso & Dell’Angelo 2010; Dell’Angelo et al. 2013, 2021b). Pliocene: central Mediterranean, Italy: Piedmont: Vintebbio; Emilia-Romagna: Cava di Campore (this study).