Lucilina colantonii, 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 : 425-427

Lucilina colantonii n. sp.

( Fig. 15 )

Type material. Holotype: MZB 50549, intermediate valve, width 2.7 mm ( Figs 15 A–C) . Paratype: RGM.1356860, intermediate valve, width 3.9 mm ( Figs 15 D–F).

Type locality. Hurghada , Egypt (St. 16) .

Other material examined. Egypt, Hurghada: St. 13: 2 intermediate valves ( BD 213); St. 14: 2 intermediate valves ( BD 214); St. 16: 1 intermediate valve ( BD 215).

Recent material examined. Sudan, Shab Runi Reef (P078): 2 intermediate valves, Figs 15 J–L ( BD 216 , MZB 50551) ; Sudan, Sanganeb Reef (D08): 1 intermediate valve ( MZB 60260) ; Egypt, Gulf of Aqaba (P447): 4 intermediate valves, Figg 15 G–I ( BD 217 ; MZB 50550) ; Egypt, Gulf of Aqaba , Blue Hole (P447A): 1 intermediate valve ( BD 218 ) . Maximum width of the intermediate valves: 5.5 mm .

Type stage. Late Pleistocene, last interglacial MIS5e.

Etymology. This species honours the marine geologist Paolo Colantoni (1934–2015) who first introduced M.T. to the study of recent and fossil molluscs of the Gulf of Aqaba.

Diagnosis. Intermediate valve rectangular, moderately elevated, semicarinate in anterior profile, posterior margin almost straight at both sides of prominent apex, almost triangular, pleural areas with longitudinal regular striae of small, roundish granules, jugal area large, smooth, lateral areas not raised, with irregular radial striae of similar granules. Articulamentum white, apophyses small, triangular, jugal sinus wide, one slit, teeth finely grooved on upper side.

Description. Intermediate valve rectangular, L/W ratio = 0.53–0.63, anterior margin convex, moderately elevated (H/W = 0.36–0.41), semicarinate in anterior profile, side margins slightly rounded, posterior margin almost straight at both sides of prominent apex, almost triangular, forming an angle of ca 120–130°, pleural areas with longitudinal and enough regular striae of small, roundish granules, ca 10–12 on each side, with reduced spaces between the striae of granules, jugal area large, smooth, lateral areas not raised, with 6–7 irregular radial striae of similar granules, ocelli scarcely visible in anterior third. Granules of longitudinal striae entirely covered by aesthetes of the same dimensions, not regularly arranged.

Articulamentum white, apophyses small, triangular, jugal sinus wide, one slit, slit rays not indicated, teeth finely grooved on upper side.

Remarks. Only poorly preserved and often incomplete intermediate valves are present in the studied material. The species is similar to Lucilina aegyptiaca n. sp., from which it differs in several characters ( Tab. 3).

The distribution of the aesthetes on the granules of the longitudinal striae is unusual, they are of the same di- mensions and arranged without a particular order, in contrast to the norm (generally with one or more central macroaesthetes and several microaesthetes arranged along the edge of the granule).

Numerous valves of Lucilina colantonii n.sp. were identified in extant Red Sea material still unpublished, mixed in samples initially labeled L. sueziensis and L. perligera . Two such valves are illustrated for comparison ( Fig. 15 G–L). No significant differences appear between extant and fossil valves. The extant valves are well preserved and show additional characters not preserved in the fossil state, namely the presence of longitudinal striae of small roundish granules with a diameter up to 60 µm, and ocelli with a diameter of 33–37 µm.

Distribution. Late Pleistocene: Egypt (Hurghada: this study). Present-day (this study): Sudan, Sha’ab Rum Reef, Sanganeb Reef; Egypt, Gulf of Aqaba (Blue Hole).

Figures

FIGURE 15. Lucilina colantonii n. sp. A–F. Egypt, Hurghada (St. 16), Late Pleistocene (last interglacial MIS5e). A–C. Holotype, MZB 50549, intermediate valve, width 2.7 mm, dorsal, ventral and frontal views. D–F. Paratype, RMNH xxx, intermediate valve, width 3.9 mm, dorsal and frontal views, and detail of tegmentum surface of pleural area. G–L. Present-day. G–I. Egypt, Gulf of Aqaba (P447), MZB 50550, intermediate valve, width 4 mm, dorsal view (G), detail of tegmentum surface of pleural and lateral areas (H) and detail of granules of pleural area (I). J–L. Sudan, Shab Runi Reef (P078), MZB 50551, intermediate valve, width 3.6 mm, dorsal view (J), and detail of tegmentum surface of pleural (K) and lateral (L) areas. Scale bar: 100 µm (F, H, K, L); 50 µm (I).