Abyssothyris Thomson, 1927

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 : 429

Genus Abyssothyris Thomson, 1927

TYPE SPECIES. — Terebratula wyvilli Davidson, 1878 , by original designation ( Thomson 1927: 190).

Abyssothyris wyvillei ( Davidson, 1878) ( Fig. 6 I-L)

Terebratula Wyvilli Davidson, 1878: 436 .

Terebratula Wyvillii – Davidson 1880: 27, pl. 2, figs 7, 9. Liothyris Wyvillii – Davidson 1886: 15, 16, pl. 2, figs 10-14 (not 8, 9).

Terebratula wywillei – Blochmann 1908: 625.

Abyssothyris wyvillei – Cooper 1982: 8, pl. 2, figs 13-17; 1983: pl. 2, figs 1-4. — Zezina 1985:147; 1998: 70-71. — Foster 1989: 282, 283, figs 9.1-9.3, 10.1-10.10. — Laurin 1997: 432-434, figs 19, 20, 43m-r. — Bitner 2006b: 18-20, fig. 1f-m.

MATERIAL EXAMINED. — Fiji. MUSORSTOM 10, Viti Levu, stn CP 1361, 2 complete specimens.

BORDAU 1, Lau Ridge, stn DW 1408, 3 complete specimens. — Stn CP 1409, 1 complete specimen. — Stn CP 1413, 1 complete specimen.

DEPTH RANGE. — 550-1091 m.

MEASUREMENTS. — See Table 6.

REMARKS

Abyssothyris wyvillei was reported from the Fiji Islands by Bitner (2006b). This small, smooth species is characterized by its deeply unisulcate anterior commissure, and cardinalia with a distinct half-elliptical cardinal process, long inner socket ridges and well-developed fulcral plates. The outer hinge plates are triangular and moderately wide. The loop is very short, rounded

Station No. Length Width Thickness Figure

CP 1361 9.7 10.5 6.1 Fig. 6 I-L CP 1361 9.8 9.8 5.8 – CP 1409 9.3 9.7 6.3 –

anteriorly with a transverse band weakly medially folded ( Fig. 6L ). The crural processes are short and bluntly pointed.

The specimens from Fiji are most similar to those from the New Caledonia region ( Laurin 1997). They differ from other specimens hitherto described in having smaller foramen ( Cooper 1982, 1983; Foster 1989).

Externally A. wyvillei is very similar to another species, Nipponithyris lauensis n. sp., but these species can be easily distinguished by their internal structures.

The specimens from the Miocene of Fiji described by Cooper (1978) as Abyssothyris briggsi are close in size and outline to A. wyvillei but they differ from the recent species in the much narrower loop.

Figures

FIG. 6. — A-H, Xenobrochus rotundus n. sp., Fiji, Lau Ridge, BORDAU 1, stn DW 1469, 314-377 m, SEM: A-D, ventral, dorsal, lateral and anterior views of complete specimen,holotype (MNHN BRA-3075);E, F, inner views of ventral and dorsal valves,paratype (MNHN BRA-3076); G, H, dorsal view of complete specimen (G) and enlargement of dorsal interior (H) to show brachial skeleton, paratype (MNHN BRA-3077);I-L, Abyssothyris wyvillei (Davidson,1878),complete specimen (MNHN BRA-3074),Fiji,Viti Levu,MUSORSTOM 10, CP 1361; I-K, dorsal, lateral and anterior views; L, SEM micrograph of dorsal interior to show cardinalia and brachidium. Scale bars: A-G, 2 mm; H, L, 1 mm; I-K, 0.5 cm.