Lucilina aegyptiaca, Dell’Angelo & Landau & Sosso & Taviani, 2020

Dell’Angelo, Bruno, Landau, Bernard M., Sosso, Maurizio & Taviani, Marco, 2020, Late Pleistocene Red Sea Mollusca: 1. Polyplacophora, Zootaxa 4772 (3), pp. 401-449 : 424-425

Lucilina aegyptiaca n. sp.

( Fig. 14 )

Type material. Holotype: MZB 50546, intermediate valve, width 4 mm ( Figs 14 A–D) . Paratypes: RGM.1356859, intermediate valve, width 3mm; MZB 50547, tail valve, width 3 mm ( Figs 14 E–H) .

Type locality. Hurghada , Egypt (St. 13) .

Other material examined. Egypt, Hurghada (St. 13): 5 valves (4 intermediate and 1 tail) ( BD 212).

Recent material examined. Zabargad Island (13/30): 2 intermediate valves ( Figs 14 I–L) ( MZB 50548).

Maximum width. - / 4.4 / 3 mm.

Type stage. Late Pleistocene, last interglacial MIS5e.

Etymology. The name refers to the country ( Egypt) providing all the material belonging to this new species known to date.

Diagnosis. Intermediate valve rectangular, moderately elevated, subcarinated in anterior profile, posterior margin almost straight at both sides of prominent apex, almost triangular; tail valve semicircular, mucro small, not very

prominent, in subcentral position, antemucronal slope almost straight, postmucronal slope convex. Tegmentum sculptured with irregular radial striae of roundish granules on lateral areas of intermediate valves and postmucronal area of tail valve; central area of intermediate valves and postmucronal area of tail valve sculptured with irregular longitudinal striae of ellipsoidal granules, with reduced interspace. Articulamentum white, apophyses rounded, trapezoidal in tail valve, jugal sinus wide, slit formula: -/1/8, teeth of tail valve slightly forwardly directed.

Description. Intermediate valve rectangular, L/W ratio = 0.60, anterior margin convex, moderately elevated (H/W = 0.42), subcarinated in anterior profile, side margins rounded, posterior margin almost straight at both sides of prominent apex, almost triangular, forming angle of ca 130°, pleural areas with ca 30–35 longitudinal, irregular striae of granules (with reduced interspace, larger towards lateral sides), present, but less evident on jugal area, ellipsoidal granules, drop shaped, widely spaced, 60 µm wide and up to 100 µm long, in some cases tending to be more roundish towards lateral sides ( Fig. 14A ), lateral areas not raised, with irregular radial striae of more roundish granules, ocelli scarcely visible in anterior third.

Tail valve semicircular, length ca half width (L/W = 0.52), anterior margin slightly sinuose, mucro small, not very evident, in subcentral position, antemucronal slope almost straight, postmucronal slope convex, antemucronal area sculptured like pleural area of intermediate valves, postmucronal area with irregular sculpture like lateral areas of intermediate valves, ocelli randomly dispersed in postmucronal area.

Articulamentum white, apophyses rounded, trapezoidal in tail valve, jugal sinus wide, slit formula: -/1/8, slit rays not indicated, teeth of tail valve slightly forwardly directed, all teeth finely grooved on upper side, denticulated on outer edge, eaves narrow, solid.

Remarks. Only a few poorly preserved and often incomplete intermediate valves and two tail valves from a single locality are present in the studied fossil material. The exit holes of the canals of the aesthetes embedded in the tegmentum are clearly visible in the pleural areas ( Fig. 14B ).

Lucilina aegyptiaca n. sp. is similar to L. confusa n. sp. and L. colantonii n. sp., from which it differs in numerous characters, summarised in Tab. 2.

Numerous intermediate valves of Lucilina aegyptiaca n. sp. are present in the extant material from the Red Sea expeditions (currently under study, unpublished), mixed in samples initially labeled as L. sueziensis and L. perligera . One of these valves is illustrated for comparison ( Fig. 14 I–L). No differences were observed between the extant and fossil valves. The extant valves are well preserved, and we can give some additional information, e.g. the irregular radial striae of lateral areas ( Fig. 14K ), with granules oval/roundish, length up to 100 µm, ocelli with a diameter of 44–48 µm. We can therefore confirm the presence of this species in the present-day chiton fauna of the Red Sea.

Distribution. Late Pleistocene: Egypt (Hurghada: this study). Present-day: Red Sea, Zabargad island (this study).

Figures

FIGURE 14. Lucilina aegyptiaca n. sp. A–H. Egypt, Hurghada (St. 13), Late Pleistocene (last interglacial MIS5e). A–D. Holotype, MZB 50546, intermediate valve, width 4 mm, dorsal view (A), detail of tegmentum surface of pleural area (B), ventral (C) and frontal (D) views. E–H. Paratype, MZB 50547, tail valve, width 3 mm, dorsal, ventral, lateral and posterior views. I–L. Present-day, Zabargad Island, st. 13/30, MZB 50548, intermediate valve, width 3.8 mm, dorsal view (I), detail of tegmentum surface of pleural area (J), of lateral areas (K) and frontal view (L). Scale bar: 100 µm (B, K).