Rhynchostreon cf. suborbiculatum ( Lamarck, 1801 ), Lamarck, 1801

Musavu Moussavou, Benjamin, 2017, Systematics, palaeoecology and taphonomy of Turonian oysters from the northern Gabon Coastal Basin, Geodiversitas 39 (2), pp. 213-224 : 216-218

Rhynchostreon cf. suborbiculatum ( Lamarck, 1801)

( Fig. 3 B, C)

Gryphaea cf. suborbiculata Lamarck, 1801: 398, figs in Knorr (1801: pl. 62; figs 1, 2).

Rhynchostreon cf. columbum mermeti – Freneix 1972: 89, pl. 5, figs 4, 5.

Rhynchostreon cf. suborbiculatum – Fischer 1980: 250, pl. 121; figs 7, 8. — Malchus 1990: 132-133. — Videt 2003: 24, pl. 5, figs 1-8.

Rhynchostreon mermeti – Malchus 1990: 128, pl. 8, figs 15-17; pl. 9, figs 5-21.

MATERIAL. — 1 specimen (MDG/LBV/Lm-9).

OCCURRENCE. — Upper Cretaceous of Europe ( Fischer 1980; Videt 2003), North Africa ( Freneix 1972; Malchus 1990). In Gabon, this species is recorded for the first time.

DESCRIPTION

Shell, represented only by left valve, is large, inequivalve, elliptical shape in outline. Umbo is small, very opisthogyrate.

Anterior margin is curved into approximately semicircular shape. Posterior margin is slightly curved. Attachment area is small. Ornament consists of ribs in posterodorsal part.

REMARK

This morphotype is doubtfully assigned to R. suborbiculatum ( Lamarck, 1801) because of the presence of ribs in posterodorsal part of left valve.

R. suborbiculatum shows great similarities to R. mermeti ( Coquand, 1862). For discussion concerning this topic, the reader is referred to Freneix (1972), Freneix & Viaud (1986), Malchus (1990), Aqrabawi (1993), Cooper (1995), Seeling & Bengtson (1999). In our material we have only one specimen.For this reason we prefer to consider R. mermeti as a synonym R. suborbiculatum.

Figures

FIG. 3. — A, Gyrostrea A MDG/LBV/Lm-13;B, C, Rhynchostreon cf.suborbiculatum (Lamarck,1801) MDG/LBV/Lm-9;D-F, Gryphaeostrea sp.;D-E, MDG/LBV/Lm- 7.1, F. MDG/LBV/Lm-7.2; G, H, Curvostrea tevesthensis (Coquand,1862) MDG/LBV/Lm-11;I-M, Ilymatogyra (Afrogyra) africana (Lamarck, 1801); I, J, MDG/LBV/ Lm-8.3,K.MDG/LBV/Lm-8.2,L-M.MDG/LBV/Lm-8.1;N, Q, Ostreidea gen.et sp.;indet MDG/LBV/Lm-34;O,P.Pycnodonte sp.MDG/LBV/Lm-10.Scale bar:1 cm.