Argyrotheca Dall, 1900

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 : 588

Genus Argyrotheca Dall, 1900

TYPE SPECIES. — Terebratula cuneata Risso, 1826 , by original designation of Dall (1900: 44).

Argyrotheca cuneata ( Risso, 1826) ( Fig. 4 A-G; Table 4)

Terebratula cuneata Risso, 1826: 388 , pl. 12, fig. 179.

Argyrotheca cuneata – Logan 1979: 45-49, text-figs 11, 12; pl. 4, figs 1-12. — Bitner 1990: 138-140, textfig. 5-6, pl. 4, figs 1-9; 1993: 149-150, pl. 2, figs 1-6; pl. 3, figs 1-6. — Taddei Ruggiero 1996: 202. — Bitner & Pisera 2000: 9, pl. 1, figs 1-7. — Kroh 2003: 148, pl. 1, figs 1-3. — Bitner & Dulai 2004: pl. 3, figs 2-6. — Bitner & Kaim 2004: 196, fig. 2A-C. — Álvarez & Emig 2005: 149-153, figs 25A-B, 27A, C, E, 44, 45, 67-69. — Dulai 2007: 4, fig. 3.1-7.

MATERIAL EXAMINED. — Peyrère: six complete specimens, six ventral and three dorsal valves, MNHN.F.A46507- A46512.

OCCURRENCE. — fflis species is very common in the Miocene of the Central Paratethys and Neogene of the Mediterranean region. Today it lives in the Mediterranean Sea and North Atlantic ( Brunton & Curry 1979; Logan 1979, 1983, 1988), having depth range of 5 to 645 m ( Logan 2007). Argyrotheca cf. cuneata was also recorded from off Brazil ( Simões et al. 2004).

REMARKS

Argyrotheca cuneata is rare in the studied assemblage and was found in only one locality.ffle shell is small, rectangular with greatest width usually at hinge line. ffle shell surface is covered with 6-8 single, low and rounded ribs. ffle foramen is large, triangular with a wide pedicle collar supported by a septum. ffle teeth are widely separated lying parallel to the hinge line. ffle dorsal median septum is high, triangular in profile with 3-4 serrations.

Argyrotheca cuneata can be distinguished from a second Argyrotheca species , A. bitnerae Dulai, 2011 and Joania cordata ( Risso, 1826) in rectangular outline and ribbed surface. Additionally, A. cuneata differs from J. cordata in lacking tubercles on the inner margin. ffle absence of margin tubercles distinguishes it also from Joania peyrerensis n. sp.

In shell outline and ornamentation A. cuneata resembles Megathiris detruncata , being, however, easily distinguishable internally from the latter species; M. detruncata has three septa on the dorsal valve.

Figures

FIG. 4. — Argyrotheca cuneata (Risso, 1826), Peyrère, Upper Oligocene; A, dorsal view of complete specimen, MNHN.F.A46507; B-E, inner and oblique lateral views of dorsal valves MNHN.F.A46508-A46509; F, G, ventral and dorsal interiors of one specimen, MNHN.F.A46510-A46511. All SEM. Scale bars: A, D, E, 1 mm; B, C, F, G, 500 µm.