Pelagodiscus Dall, 1908

Bitner, Maria Aleksandra, 2008, New data on the recent brachiopods from the Fiji and Wallis and Futuna islands, South-West Pacific, Zoosystema 30 (2), pp. 419-461 : 422-424

Genus Pelagodiscus Dall, 1908

TYPE SPECIES. — Discina atlantica King, 1868 , by original designation ( Dall 1908: 440).

Pelagodiscus atlanticus ( King, 1868) ( Fig. 2 )

Discina atlantica King, 1868: 170 .

Discinisca atlantica – Davidson 1888: 200-202, pl. 26, figs 18-22.

Pelagodiscus atlanticus – Dall 1908: 440. — Thomson 1927: 130, 131, fig. 37. — Helmcke 1940: 230-234. — Cooper 1973c: 10, pl. 5, fig. 36. — Foster 1974: 39, 40, fig. 13. — Zezina 1975: 903-909, figs 1-7; 1981: 8; 1985: 107; 1987: 555. — Lee 1987: 51, 52, fig. 1c-f. — Laurin 1997: 417. — Álvarez & Emig 2005: 103, fig. 56a-h.

MATERIAL EXAMINED. — Wallis and Futuna. MUS- ORSTOM 7, Combe Bank, stn CP 621, 20 specimens.— Stn CP 623, 4 specimens.

DEPTH RANGE. — 1280-1300 m.

MEASUREMENTS. — See Table 1.

R EMARKS

Pelagodiscus atlanticus is one of the most widespread brachiopods, being known from the Atlantic, Pacific and Indian oceans, as well as from northern and southern hemispheres( Emig 1997).The shell is small, oval to subcircular, very thin, chitinophosphatic; the surface smooth with numerous concentric growth lines. The apex is near the valve centre. This species is characterized by its dorsal mantle-edge with numerous setae, short around posterior margin and very long around anterior margin ( Fig. 2C ). Although having a very wide depth range from 366 to 6000 m ( Zezina 1985), P. atlanticus occurs more often below 1000 m and is regarded as a very deep-water species.

Subphylum CRANIIFORMEA Popov, Bassett, Holmer & Laurie, 1993 Class CRANIATA Williams, Carlson, Brunton, Homler & Popov, 1996 Order CRANIIDA Waagen, 1885 Superfamily CRANIOIDEA Menke, 1828 Family CRANIIDAE Menke, 1828

Figures

FIG. 2.— Pelagodiscus atlanticus (King,1868),Wallis and Futuna,MUSORSTOM 7:A, B, dorsal view and enlargement (B) to show details of setae (MNHN BRA-3056),stn CP621,1280-1300 m; C, dorsal view (MNHN BRA-3057),stnCP 621,1280-1300 m;D, ventral view of complete specimen(MNHN BRA-3058),stn CP623,1280-1300m; E,F, inner viewof ventralvalve withsoft tissue,visible tracesof dorsalvalve and dorsal setae,and enlargement (F) of lophophore (MNHN BRA-3059),stn CP 623,1280-1300 m. Scale bars:A,C,2 mm;B,D, E,1 mm;F,100 μm.