Callochiton vanninii Ferreira, 1983

Dell’Angelo, Bruno, Landau, Bernard M., Sosso, Maurizio & Taviani, Marco, 2020, Late Pleistocene Red Sea Mollusca: 1. Polyplacophora, Zootaxa 4772 (3), pp. 401-449 : 410-411

Callochiton vanninii Ferreira, 1983

( Fig. 5 )

Callochiton vanninii Ferreira 1983, p. 259 , figs 11–19; Strack 1993, p. 6, pl. 2, fig. 8; Bosch et al. 1995, p. 189; Kaas & Van Belle 1998, p. 194; Dekker & Orlin 2000, p. 7; Slieker 2000, p. 46, pl. 11, fig. 5; Schwabe 2003, p. 23; Anseeuw & Terryn 2004, p. 6, fig. 37; Dell’Angelo et al. 2004, p. 51, pl. 2, figs 9–14; Kaas et al. 2006, p. 22, fig. 3, map 20; Dinapoli & Janssen 2009, p. 5, pl. 2a– d; Dell’Angelo et al. 2010a, p. 11; Mohammadian 2011, p. 211; Dell’Angelo et al. 2012, p. 156; Blatterer 2019, p. 49, pl. 1, fig. 3 a-m.

Non Callochiton vanninii ; Kaas & Van Belle 1985b, p. 44, fig. 18; Kaas 1985, p. 327; Kaas 1986, p. 10, fig. 6 (= Callochiton levatus Kaas, Van Belle & Strack, 2006 ).

Type material. Holotype: MZUF 4098; Paratype: CAS 031758.

Type locality. Gesira , Somalia .

Material examined. Saudi Arabia, Gulf of Aqaba (Ash Shaykh Humayd: this study): St. 7: 1 tail valve ( MZB 50590); St. 9: 1 intermediate valve ( MZB 50591). Egypt, Hurghada: St. 12: 11 valves (1 head, 8 intermediate and 2 tail) ( BD 185); St. 13: 96 valves (12 head, 70 intermediate and 14 tail), Figs 5 A–L ( BD 186; MZB 50528; RGM.1356851). Egypt, Hamata: St. 18: 1 intermediate valve ( MZB 60271). Maximum width: 2.5 / 3.7 / 3.5 mm.

Description. Head valve semicircular, posterior margin widely V-shaped, front slope slightly convex.

Intermediate valves rectangular, front margin sinuous, weakly concave in wide central part, convex and somewhat slanting at pleurae, moderately elevated (H/W = 0.30–0.48), anterior profile rounded to subcarinated, side margins rounded, posterior margin slightly concave at both sides of bluntly protruding apex, lateral areas raised, clearly defined by diagonal depression.

Tail valve semicircular, L/W = 0.60–0.65, front margin straight in jugal part, mucro in anterior position, little elevated, forwardly directed, antemucronal and postmucronal slopes almost straight.

Tegmental surface minutely granulose and microscopically striated, longitudinally on central and antemucronal areas, radially on head valve, lateral and postmucronal areas, shell eyes not visible.

Articulamentum with apophyses very wide, short, slightly rounded, connected across narrow, shallow sinus by short jugal plate, insertion plates well developed, slit formula 15–20/2/17–21, slits deep, neatly cut, slit rays clearly visible, teeth sharp, somewhat roughened on upper side and outer edge, eaves narrow, porous.

Remarks. A detailed description of this species was provided by Kaas et al. (2006). Callochiton vanninii Ferreira, 1983 is very similar to Callochiton levatus Kaas, Van Belle & Strack, 2006 from Madagascar, Réunion, Mauritius and Chagos Archipelago, from which it can be distinguished mainly by the different shape of the tail valve (broadly oval with an extended, but not laterally protruding, articulamentum in C. levatus , semicircular with wide, but short, apophyses in C. vanninii ), the different slit formula (12–14/1–2/ 10–12 in C. levatus vs 16/2–3/ 16 in C. vanninii ) ( Strack 1993; Kaas et al. 2006) and by differences in their radular teeth ( Schwabe 2003).

Callochiton vanninii is present at only three sites sampled, but only at one (St. 13) is it represented by a large number of valves. The valves are not well preserved, often eroded, and usually incomplete, especially the intermediate ones.

The intermediate valves show a variability in the dorsal elevation, the H/W ratio ranges from 0.30 to 0.48, with the anterior profile subcarinate in the valves with lower values of H/W ratio ( Figs 5 D–F, H/W = 0.30), tending to be rounded in the apex with the growth of this ratio ( Fig. 5G, H /W = 0.48). Also the tail valves show a certain variability in shape (L/W ratio).

The number of slits of head and tail valves is higher than that reported for this species ( Kaas et al. 2006: 15–16 for both valves), 20 and 21, respectively. We illustrate two tail valves, with 18 slits ( Figs 5 H–I, L/W = 0.60) and 21 slits ( Figs 5 J–L, L/W = 0.65), respectively.

Despite the differences highlighted in the number of slits, we provisionally attribute the studied material to Callochiton vanninii , pending better preserved material to further characterise the fossil species.

This is the first report of this species as a fossil.

Distribution. Late Pleistocene: Saudi Arabia, Gulf of Aqaba (Ash Shaykh Humayd); Egypt (Hurghada, Hamata: this study). Present-day: Indian Ocean: Red Sea, Somalia, Madagascar, Arabian Gulf ( Bahrein), Socotra Island ( Dinapoli & Janssen 2009; Blatterer 2019).

Figures

FIGURE 5. Callochiton vanninii Ferreira, 1983. A–L. Egypt, Hurghada (St. 13), Late Pleistocene (last interglacial MIS5e). A– C. MZB 50528a, head valve, width 2.3 mm, dorsal, ventral and lateral views. D–F. MZB 50528b, intermediate valve, width 2.3 mm, dorsal, ventral and frontal views. G. MZB 50528c, intermediate valve, width 3.4 mm, frontal view. H–I. MZB 50528d, tail valve, width 3.5 mm, dorsal and ventral views. J–L. MZB 50528e, tail valve, width 2.3 mm, dorsal, ventral and lateral views.