Dallithyris Muir-Wood, 1959

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 : 431-433

Genus Dallithyris Muir-Wood, 1959

TYPE SPECIES. — Dallithyris murrayi Muir-Wood, 1959 , by original designation (Muir-Wood 1959: 305).

Dallithyris pacifica Bitner, 2006 ( Fig. 7 J-L)

Dallithyris pacifica Bitner, 2006b: 20-22 , fig. 2a-j.; Bitner 2007: 495, 496, figs 1i-k, 2c, d.

MATERIAL EXAMINED. — Fiji. MUSORSTOM 10, Bligh Water, stn CP 1331, 8 complete specimens, 2 ventral valves. — Stn CP 1332, 9 complete specimens. — Stn CP 1335, 1 complete specimen. — Stn CC 1336, 4 complete specimens.

BORDAU 1, Lau Ridge, stn DW 1432, 1 young complete specimen. — Stn DW 1465, 1 young complete specimen.

DEPTH RANGE. — 290- 799 m.

MEASUREMENTS. — See Table 8.

REMARKS

Dallithyris pacifica was already recorded from the Fiji region (for detailed description, see Bitner 2006b, 2007). This species differs from two other recent Dallithyris species , D. murrayi Muir-Wood, 1959 and D. fulva (Blochmann, 1906) , in being smaller, triangular in outline and having rectimarginate anterior commissure (Muir-Wood 1959; Cooper 1983). Recently D. pacifica was also found in the region of the Austral Islands, French Polynesia ( Bitner 2007).

Dallithyris was also recognized in the Neogene deposits of Fiji ( Cooper 1978). The fossil specimens are much smaller than D. pacifica , however, like the recent material they are characterized by the subtriangular outline and rectimarginate commissure.

In her recent paper Zezina (2005) synonymised three genera: Dallithyris , Stenosarina Cooper, 1977 and Dolichozygus Cooper, 1983 . However, in the opinion of the present author those genera display sufficient differences to be separated. Both Dallithyris and Stenosarina have similar loops with a broad transverse band which possesses a strong median fold, but the loop in Stenosarina is much narrower than that in Dallithyris (see Bitner 2006b: fig. 2j, k). The crural bases in Dallithyris are poorly defined, while those in Stenosarina are elevated along the inner margins of the outer hinge plates. In turn, the transverse band in Dolichozygus lacks that sharply arched fold present in both former genera. Thus, in the present paper Dallithyris is still considered as a separate genus, as in the new edition of the Treatise (see Lee & Smirnova 2006).

Superfamily CANCELLOTHYRIDOIDEA

Figures

FIG. 7. — A-D, Terebratulina japonica (G. B. Sowerby, 1846), Fiji: A, dorsal view of complete specimen (MNHN BRA-3079), Lau Ridge, BORDAU 1, stn DW 1413, 669-676 m; B-D, dorsal, lateral and anterior views of complete specimen (MNHN BRA-3080), Bligh Water, MUSORSTOM 10, stn CP 1330, 567-699 m; E-I, Terebratulina australis Bitner, 2006,Fiji,Lau Ridge BORDAU 1; E, dorsal view of young complete specimen (MNHN BRA-3081),SEM,stn DW 1479,450-460 m; F-I, ventral,dorsal,lateral andanterior viewsof complete specimen (MNHN BRA-3082),stn DW 1485,700-707 m; J-L, Dallithyris pacifica Bitner,2006,dorsal,lateral and anterior views of complete specimen (MNHN BRA-3078), Fiji, Bligh Water,MUSORSTOM 10, stn DW 1331, 694-703 m. Scale bars:A-D, F-I, 0.5 cm; E, 2 mm; J-L, 1 cm.