Megathiris d’Orbigny, 1847

Bitner, Maria Aleksandra, Lozouet, Pierre & Cahuzac, Bruno, 2013, Upper Oligocene (Chattian) brachiopod fauna from the Aquitaine Basin, southwestern France and its paleoenvironmental implications, Geodiversitas 35 (3), pp. 579-606 : 586-587

Genus Megathiris d’Orbigny, 1847

REMARKS

Dall (1920) showed that the first binominal valid name given to this species was Anomia detruncata Gmelin, 1791 , and this should therefore be used for the type species (see also fflomson 1927: 213).

Megathiris detruncata ( Gmelin, 1791) ( Fig. 3 A-M; Table 3)

Anomia detruncata Gmelin, 1791: 3347 .

Megathyris decollata – Peyrot 1932: 485, 486, pl. 17, figs 11-13.

Megathiris detruncata – Logan 1979: 55-59, text-figs 15, 16; pl. 6, figs 1-13. — Gaetani & Saccà 1985: 17, 18, pl. 9, figs 10-12; pl. 10, figs 11-14. — Taddei Ruggiero 1985: 369-371, pl. 5, figs 1-9; pl. 6, figs 1-6; pl. 7, figs 1-9, 14; 1994: 208, pl. 3, figs 6-9; 1996: 202. — Bitner 1990: 135-138, text-figs 3, 4; pl. 3, figs 1-8; pl. 6, figs 1-7. — Bitner & Moissette 2003: 473, 474, fig. 6G, H. — Kroh 2003: 147, 148, pl. 1, figs 4-6. — Bitner & Dulai 2004: 74, 76, pl. 3, figs 11-15; 2008: 35, 36, fig. 5.1-4. — Álvarez & Emig 2005: 147, 148, figs 25C, 63-66. — Dulai 2007: 2, 3, fig. 2.1-2; 2010a: 26, pl. 3, fig. 1a, b. — Bitner & Schneider 2009: 127, fig. 6A-C.

MATERIAL EXAMINED. — Peyrère: 120 complete specimens, 32 ventral and 42 dorsal valves, MNHN.F.A46502 and

A46554.— Abesse:12 complete specimens, 72 ventral and 101 dorsal valves MNHN.F.A46491-A46501. — Estoti: five ventral valves, MNHN.F.A46503. — Bezoye: four complete specimens, three ventral and 17 dorsal valves, MNHN.F.A46504. — Bélus: ten complete specimens, three ventral and five dorsal valves, MNHN.F.A46505 and A46506.

OCCURRENCE. — fflis species is known in the fossil record since the Eocene and lives today in the Mediterranean and the north-eastern North Atlantic at the depth from 5 to 896 m ( Logan 2007).Its occurrence in the Caribbean Sea reported by Cooper (1977) is questionable (see also Logan 2007). REMARKS

Megathiris detruncata is one of the most common species (more than 400 specimens) in the investigated assemblage, found in five localities. It was already recorded from the studied area ( Peyrot 1932; Lozouet 2004). ffle specimens from the Aquitaine Basin correspond well to those hitherto described (e.g., Logan1979; Taddei Ruggiero 1985; Bitner 1990; Bitner & Schneider 2009).ffle shell is small(our largest specimen is a dorsal valve 7.0 long and 8.1 mm wide), transversely ovate in outline, covered with few wide, rounded ribs. ffle foramen is large, triangular, bordered by two narrow deltidial plates. Internally, this species is characterized by the presence of three septa on a dorsal valve what makes it an easily recognizable species.

Figures

FIG. 3. — Megathiris detruncata (Gmelin, 1791), Upper Oligocene, Abesse: A, B, D, dorsal views of complete specimens, MNHN.F.A46491-A46493;C, inner view of ventral valve,MNHN.F.A46494;E, inner view of dorsalvalve of young individual,MNHN.F.A46495; F-M, inner and oblique views of dorsal valves, and enlargements (H, M) to show details of septa and loop, MNHN.F.A46496-A46498. All SEM. Scale bars: A, H, 500 µm; B, D-G, K-M, 1 mm; C, I, J, 2 mm.