Callochiton zigzag Šulc, 1934

Callochiton zigzag Šulc, 1934

Fig. 54 View FIGURE 54

Callochiton zig-zag Šulc, 1934, p. 12 , pl. 1, figs 17–19; Malatesta 1962, p. 159; Dell’Angelo et al. 2018b, p. 53, tab. 17; Dell’Angelo et al. 2020b, p. 52, tab. 9.

Callochiton zigzag ; Bałuk 1971, p. 461, pl. 5, figs 6–8; Van Belle 1981, p. 81; Bałuk 1984, p. 290; Studencka & Studencki 1988, p. 43, tab. 2; Ruman & Hudáčková 2015, p. 166.

Type material. Holotype, unknown, not present in the Šulc collection at NHMW, intermediate valve ( Šulc 1934: pl. 1, fig. 18), Fig. 54A View FIGURE 54 .

Type locality. Kninice ( Czech Republic) .

Type stage. Middle Miocene.

Material examined. No actual material available, only descriptions and illustrations from the literature ( Fig. 54A–D View FIGURE 54 ). Maximum width of the valves: 3 / 6.5 / 6 mm.

Description. Head valve semielliptical. Intermediate valves broadly rectangular, keeled, anterior margin convex, side margins slightly rounded, posterior margin almost straight with a small apex, lateral areas raised. Tail valve semielliptical, anterior margin slightly convex, mucro subcentral or slightly anterior.

Tegmentum rough. HV, LA and PMA finely granulose, sculptured with zigzagging wrinkles. CA and AMA sculptured with closely and regularly spaced fine pits which radially diverge from apex.

Articulamentum with apophyses narrow, widely spaced and rounded, connected at jugum by a lamina, insertion plates with many slits, slit formula 30–33 / 5–7 / 30, slit rays well visible.

Remarks. Callochiton zigzag Šulc, 1934 is a poorly known species from the Paratethys, only reported by Šulc (1934) from the Czech Republic, and by Bałuk (1971, 1984) from Korytnica ( Poland). The sculpture of the valves is, however, very characteristic and different from all other Callochiton species from the European Neogene. The presence of pigmented aesthetes (present in many species of the genus Callochiton , see Schwabe 2010; Speiser et al. 2011) has not been confirmed in C. zigzag .

Comparisons. Callochiton zigzag has the highest number of slits compared to the other Callochiton discussed here, and the sculpture also differs (see Tab. 8).

Distribution. Middle Miocene: Central Paratethys (Langhian-Serravallian): Czech Republic: Kninice, Borač, Židlochovice ( Šulc, 1934); Poland: Korytnica ( Bałuk, 1971, 1984).