Callochiton, Gray, 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 : 411-412

Callochiton sp.

( Fig. 6 )

Material examined. Egypt, Hurghada : St. 13: 1 intermediate valve, width 4 mm, Figs 6 A–D ( MZB 50529) .

Description. Intermediate valves trapezoidal, rounded in anterior profile, elevated (height/width ratio 0.61), anterior margin almost straight in jugal area, lateral areas weakly raised.

Tegmentum surface appears rough, sculptured with fine granules, fusing into continuous longitudinal lines in central area, radially in lateral areas.

Articulamentum with short, wide apophyses connected at jugum by lamina, insertion plates short, with two slits, slit rays visible.

Remarks. This intermediate valve is characterised by the lack of longitudinal grooves on the pleural area (as in C. vanninii ), the rounded anterior profile and the strong elevation (H/W = 0.61), higher than that seen in intermediate valves of C. vanninii (H/W = 0.30–0.48). These characters do not agree with those of the other named Indian Ocean Callochiton species, C. clausadeae Kaas & Van Belle, 1985b (from Madagascar, Mauritius, Réunion, and the Maldive Islands), C. levatus Kaas & Van Belle, 1998 (from Madagascar, Réunion, Mauritius and Chagos Archipelago) and C. christamariae Schwabe, 2003 (from Mauritius).

Two fossil species of Callochiton have a similar dorsal elevation. Callochiton calcatus Dell’Angelo & Palazzi, 1994 (H/W = 0.65–0.72), known from the Recent Mediterranean and the submerged Pleistocene of the Tyrrhenian Sea geographic area between Capraia and Capo Corso, Italy ( Dell’Angelo & Giusti 1997), differs from Callochi- ton sp. mainly by the presence of longitudinal grooves on the pleural areas and the more angulated intermediate valves. Callochiton pouweri Dell’Angelo, Landau, Van Dingenen & Ceulemans, 2018b (H/W = 0.58–0.64), known from the upper Miocene of Anjou, France, differs from Callochiton sp. mainly by the presence of longitudinal grooves on the pleural areas and the valves being carinated in anterior profile.

Distribution. Late Pleistocene: Egypt (Hurghada: this study).

Figures

FIGURE 6. Callochiton sp., Egypt, Hurghada (St. 13), Late Pleistocene (last interglacial MIS5e). A–D. MZB 50529, intermediate valve, width 4 mm, dorsal view, detail of tegmentum surface of central area, ventral and frontal views. Scale bar: 100 µm (B).