Cryptoplax lanceolatus Laghi, 1977

Cryptoplax lanceolatus Laghi, 1977

Fig. 150 View FIGURE 150

Criptoplax (sic) lanceolatus Laghi, 1977, p. 114 , pl. 4, figs 17–18; Van Belle 1981, p. 46.

Cryptoplax lanceolatus ; Zanaroli 1985, tab. 2; Dulai 2005, p. 42; Dell’Angelo et al. 2007a, p. 47; Puchalski et al. 2008 (database: chiton fossil records); Dell’Angelo et al. 2016, p. 95, pl. 7, figs 26–28; Dell’Angelo et al. 2020b, p. 53, tab. 9.

Type material. MPUM 18972 (one head and one tail valve), Figs 150A–B View FIGURE 150 .

Type locality. Montegibbio ( Piedmont, Italy) .

Type stage. Miocene (Tortonian).

Material examined. Upper Miocene: Italy (Tortonian): Montegibbio: 1 intermediate valve ( MZB 32131, Figs 150C–D View FIGURE 150 ). Maximum width of the valves: 1.5 / 1.6 / 1.5 mm.

Description. Valves longer than wide. Head valve trapezoidal. Intermediate valve pentagonal, jugal area rectangular, converging in apex. Tail valve polygonal, jugal area smooth, on which are seen, aligned in parallel rows, exit holes of aesthete channels.

HV sculptured with three trapezoidal arcuate ribs, centered in apex, of increasing size, and remains of weak lumpy ribs, aligned forward, only visible on left side of HV; PLA ornamented with weak lumpy ribs aligned forward.

Articulamentum with apophyses elongated triangular in outline in intermediate valves, head valve with apical area shaping a circular segment, slits not visible on insertion plate of head valve, slit formula? / 0 / 0.

Remarks. Cryptoplax lanceolatus Laghi, 1977 was described on the basis of a head and tail valve from Montegibbio, not too well preserved, with a sculpture of weak lumpy ribs (the “deboli coste grumose” in Laghi 1977) quite different in form from the longitudinal, slightly undulated ribs typical of C. weinlandi Šulc, 1934 . Later, a single intermediate valve, also from Montegibbio, has been attributed to this species by Dell’Angelo et al. (2016).

The head valve depicted by Laghi is almost completely decorticated, the narrow insertion plate does not appear engraved, perhaps because the teeth are completely worn.

Comparisons. C. margitae Dulai, 2001 , is the species whose sculpture is closer to Cryptoplax lanceolatus (see below).

Distribution. Late Miocene: Proto-Mediterranean Sea (Tortonian): Po Basin, Italy: Montegibbio ( Laghi 1977; Dell’Angelo et al. 2016).