Leptochiton boettgeri ( Šulc 1934 )

Leptochiton boettgeri ( Šulc 1934) View in CoL

Fig. 29 View FIGURE 29

Chiton sp. Boettger, 1902, p. 180, n° 560 ( pars) ( fide Zilch 1934: 198). Lepidopleurus boettgeri Šulc, 1934, p. 5 View in CoL , pl. 1, figs 1–2; Zilch 1934, p. 198, pl. 1, figs 15–16; Van Belle 1981, p. 24; Kaas &

Van Belle 1994, p. 9; Dell’Angelo & Smriglio 1999, p. 72. Leptochiton boettgeri View in CoL ; Dell’Angelo et al. 2018b, p. 52, tab. 17. non Lepidopleurus ( Leptochiton) boettgeri View in CoL ; Dell’Angelo & Palazzi 1989, p. 72, pl. 20, 22 fig. 5; Chirli 2004, p. 4, pl. 1, figs 3–8

(= Leptochiton bedullii View in CoL Dell’Angelo & Palazzi, 1986, fide Kaas & Van Belle 1994; Dell’Angelo & Smriglio 1999). Lepidopleurus ( Lepidopleurus) srameki Šulc, 1934, p. 5 View in CoL , pl. 1, fig. 3; Van Belle 1981, p. 73. Lepidopleurus srameki View in CoL ; Bałuk 1971, p. 454, pl. 2, fig. 5; Bałuk 1984, p. 285, pl. 4, fig. 3a–b¸ Kaas & Van Belle 1994, p. 9;

Dell’Angelo & Smriglio 1999, p. 72. Leptochiton srameki ; Macioszczyk 1988, p. 51, pl. 1 fig. 9; Dell’Angelo et al. 2018b, p. 52, tab. 17.

Type material. Holotype SMF 1413 About SMF a, tail valve, width 3.2 mm ( Fig. 29A View FIGURE 29 ) , Paratype SMF1413 About SMF b, head valve, width 3.8 mm ( Figs 29B–C View FIGURE 29 ) , Paratype, SMF 1413 About SMF c_2, intermediate valve, width 4 mm ( Fig. 29D View FIGURE 29 ) , Paratype, SMF 1413 About SMF c_1, intermediate valve, width 3.4 mm ( Figs 29E–F View FIGURE 29 ) .

Type locality. Kostej ( Romania) .

Type stage. Middle Miocene.

Material examined. No actual material available, only descriptions and illustrations from the literature.

Description. Head valve semicircular, posterior margin widely V-shaped, notched in middle. Intermediate valves broadly rectangular, carinate in anterior profile, moderately elevated, anterior margin slightly convex, posterior margin almost straight, apex not developed, lateral areas slightly raised. Tail valve semicircular, mucro in central position.

Tegmentum rough. HV and PMA sculptured with radial striae of oval granules (HV 50, PA 35), not all starting from apex, but tending to branch, LA with oval granules seeming arranged in concentric growth lines and, in addition, in radial striae. CA and AMA sculptured with longitudinal striae of closely spaced roundish granules (CA 20 on each side, striae more closely spaced in jugum than on slopes, AMA 22–26, converging towards outer margins and quite far from each other).

Articulamentum without insertion laminae, with small apophyses, widely separated.

Remarks. Šulc (1934) described two species, L. srameki and L. boettgeri , considered cospecific by Dell’Angelo & Palazzi (1989), that considered L. srameki as a junior synonym of L. boettgeri . Šulc himself considered the two species very similar, highlighting as difference that “not all the radial chains of granules start from the apex”, but tend to branching (in L. boettgeri ).

Leptochiton boettgeri was established by Šulc (1934) on the basis of four valves ( Figs 29A–F View FIGURE 29 ) from the Boettger collection, previously determined by O. Boettger as Chiton sp. , while L. srameki was determined by Šulc (1934) on the basis of a single tail valve ( Fig. 29H View FIGURE 29 ). Subsequently Bałuk (1971, 1984) attributed to L. srameki two intermediate valves from Korytnica ( Poland) ( Fig. 29G View FIGURE 29 ), remarking that an exhaustive comparison is unfeasible. Another intermediate valve from Węglinek ( Poland) was reported by Macioszczyk (1988), a valve consistent with the material described by Bałuk (1971, 1984).

Dell’Angelo & Palazzi (1989) recorded the strong affinities existing between the two fossil species described by Šulc (1934) and the recent Mediterranean species Leptochiton bedullii Dell’Angelo & Palazzi, 1986, and put L. bedullii in synonymy with L. boettgeri , 1934, on the basis of a direct comparison between a tail valve ( paratype) of L. bedullii and the holotype of L. boettgeri . Kaas & Van Belle (1994) consider the two species distinct, above all on the basis of differences between the Miocene molluscan faunas and the Recent. Dell’Angelo & Smriglio (1999) accepted to keep the two species separate, considering also that L. bedullii shows some very peculiar characteristics not recorded in other Leptochiton (e.g., the cylindrical dorsal spicules of the girdle), and we agree with this interpretation.

Comparisons. The characteristics of the sculpture of Leptochiton boettgeri agree with the belonging of the species to the Leptochiton cancellatus group, see Tab. 2. The closest species is L. bedullii , as already reported by Dell’Angelo & Palazzi (1989).

Distribution. Middle Miocene: Central Paratethys (Langhian-Serravallian): Romania: Kostej ( Šulc 1934); Czech Republic: Rudoltice ( Šulc 1934); Poland: Korytnica, Węglinek ( Bałuk 1971, 1984; Macioszczyk 1988).