Lucilina sueziensis ( Reeve, 1847 )

Dell’Angelo, Bruno, Landau, Bernard M., Sosso, Maurizio & Taviani, Marco, 2020, Late Pleistocene Red Sea Mollusca: 1. Polyplacophora, Zootaxa 4772 (3), pp. 401-449 : 415-417

Lucilina sueziensis ( Reeve, 1847)

( Fig. 9 )

Chiton sueziensis Reeve 1847 , pl. 20, fig. 134.

Chiton (Tonicia) sueziensis ; Issel 1869, p. 235; Moazzo 1939, p. 220.

Chiton (Tonicia) sp.; Issel 1869, p. 318 (ex Savigny pl. 3, fig. 7).

Tonicia suezensis (sic); Sykes 1907, p. 34; Leloup 1960, p. 40, figs 6, 8, pl. 1, fig. 1; Leloup 1980, p. 12; Vine 1986, p. 125.

Lucilina sueziensis ; Lamy 1938, p. 88; Blatterer 2019, p. 52, pl. 4, fig. 10 a–n.

Tonicia sueziensis ; Ferreira 1983, p. 271, figs 25–28; Dekker & Orlin 2000, p. 7; Slieker 2000, p. 50, fig. 28; Abubakr 2004, p. 73; Dell’Angelo et al. 2004, p. 56.

Tonicia (Lucilina) sueziensis ; Kaas & Van Belle 1988, p. 124, figs 41–44; Van Belle & Wranik 1991, p. 375, fig. 21; Strack 1993, p. 19, pl. 5, fig. 1, pl. 6, figs 1–2; Bosch et al. 1995, p. 191; Kaas & Van Belle 1998, p. 182; Anseeuw & Terryn 2004, p. 15, figs 5, 50–54; Kaas et al. 2006, p. 315, fig. 129, map 158; Dinapoli & Janssen 2009, p. 20, pl. 11 a–d.

Tonicia (Lucinila) (sic) sueziensis ; Mohammadian 2011, p. 211.

Non Chiton (Tonicia) sueziensis ; Issel 1869, p. 317 (ex Savigny pl. 3, fig. 4) (= Acanthopleura vaillantii de Rochebrune, 1882 , juv., fide Kaas et al. 2006).

Type material. BMNH 1591.2.7.7, lectotype designed by Ferreira (1983: 272, figs 26–27).

Type locality. Gulf of Suez.

Material examined. Jordan, Aqaba (Yamanie) (St. 1): 5 valves (4 intermediate and 1 tail) ( MZB 60254). Saudi Arabia, Gulf of Aqaba (Ash Shaykh Humayd: this study): St. 4: 4 intermediate valves ( MZB 60255); St. 5: 3 intermediate valves ( MZB 60256); St. 7: 5 valves (4 intermediate and 1 tail) ( MZB 60257); St. 8: 7 valves (3 head and 4 intermediate), Fig. 9J ( MZB 50534); St. 9: 4 valves (1 head, 1 intermediate and 2 tail), Fig. 9L ( MZB 50535). Egypt, Hurghada: St. 12: 20 valves (2 head, 13 intermediate and 5 tail) ( BD 198); St. 13: 108 valves (13 head, 70 intermediate and 25 tail), Figs 9 A–I ( BD 199; MZB 50533a–c; RGM.1356854); St. 14: 28 valves (3 head and 25 intermediate) ( BD 200); St. 14bis: 17 valves (11 intermediate and 6 tail), Fig. 9K ( BD 201; MZB 50533d); St. 16: 46 valves (5 head, 35 intermediate and 6 tail) ( BD 202); St. 17: 1 tail valve ( BD 203). Maximum width: 3.8 / 5.7 / 7.5 mm.

Description. Head valve semicircular, posterior margin widely V-shaped, straight to weakly convex at both sides of minute apical notch, front slope slightly convex, tegmentum coarsely sculptured with up to 20 radial rows of small, warty, V-shaped rugosities, interstices each with row of minute, round to oval, black ocelli.

Intermediate valves rectangular, L/W = 0.33–0.40, front margin slightly sinuous, concave in wide central part, convex at pleurae, moderately elevated (H/W = 0.34–0.41), anterior profile subcarinated, side margins rounded, posterior margin concave at both sides of bluntly protruding apex, lateral areas not raised, sculptured like head valve, 2–4 radial rows, the anterior one with larger rugosities, defining the diagonal line, ocelli anterior on 1/3 to 1/2 of lateral area, pleural areas with up to 14 longitudinal, sinuous, slightly granulose wrinkles, fanning out anteriorly, diverging at sides, converging and gradually shortening towards wide, smooth jugal area.

Tail valve semicircular, L/W = 0.51–0.56, front margin evenly convex, straight in jugal part, mucro subcentral, not prominent, antemucronal and postmucronal slopes straight, some valves with postmucronal slope steep, strongly convex, antemucronal area sculptured like central areas, postmucronal area like head valve.

Articulamentum with apophyses wide, triangular, trapezoidal in tail valve, connected across wide, shallow sinus by short, pectinated, jugal plate, insertion plates rather long, slit formula 8–10/1/10-12, teeth strongly fluted on outside, eaves narrow, solid.

Remarks. Lucilina sueziensis is a highly variable species, especially in regards to the sculpture of the tegmentum ( Ferreira 1983; Strack 1993; Anseeuw & Terryn 2004).

The mucro of the tail valve is normally in a subcentral position, with antemucronal and postmucronal slopes almost straight or slightly concave ( Fig. 9I ), but some tail valves show a variability in morphology, with the mucro in a more posterior position, and the antemucronal and postmucronal slopes much more convex ( Figs 9 K–L). Ferreira (1983: 271) noted in the description of the tail valve “mucro prominent, central to slightly posterior; postmucro sloping at 30–45° (steeper in larger specimens)”, agreeing with the valve illustrated in Fig. 9I , but the lectotype selected and figured ( Ferreira 1983: fig 27–28) shows a postmucronal slope more similar to the valves illustrated in Fig. 9 K–L.

A similar species is Lucilina carnosa ( Kaas, 1979) from Madagascar, Mozambique, Réunion, Seychelles, Amirante, and Maldive Islands. That species was synonymised with L. sueziensis by Ferreira (1983), but differs in having stronger sculpture, the tail valve subtriangular, as well as various details of the girdle ( Kaas et al. 2006), and the two are therefore not synonymous.

The main characters of the intermediate valves of Lucilina sueziensis are reported in Tab. 3.

Distribution. Late Pleistocene: Jordan, Aqaba, (Yamanie); Saudi Arabia, Gulf of Aqaba (Ash Shaykh Humayd: this study); Egypt (Hurghada: Issel, 1869; this study). Present-day: Indian Ocean: Red Sea, Gulf of Suez, Gulf of Aden, Somalia, Seychelles, Rodriguez, and Socotra Islands ( Dinapoli & Janssen 2009; Kaas et al. 2006; Blatterer 2019).

Figures

FIGURE 9. Lucilina sueziensis (Reeve, 1847). A–I, K. Egypt, Hurghada, Late Pleistocene (last interglacial MIS5e). A–C. MZB 50533a, head valve (St. 13), width 3.4 mm, dorsal, ventral and lateral views. D–F. MZB 50533b, intermediate valve (St. 13), width 5.7 mm, dorsal, ventral and frontal views. G–I. MZB 50533c, tail valve (St. 13), width 6.5 mm, dorsal, ventral and lateral views. K. MZB 50533d, tail valve (St. 14bis), width 5.4 mm, lateral view. J, L. Saudi Arabia, Gulf of Aqaba, Ash Shaykh Humayd, Late Pleistocene (last interglacial MIS5e). J. MZB 50534, intermediate valve (St. 8), width 4.6 mm, dorsal view. L. MZB 50535, tail valve (St. 9), width 7.5 mm, lateral view.