Glyphidocythere, a new deep marine, paradoxostomatid (Ostracoda) from the Quaternary and Recent of the Indo-Pacific

Chapman’s (1910) Pseudocythere funafutiensis from 1924m off Funafuti, western Pacific is redescribed and illustrated together with additional Pleistocene and Recent material from the Coral and Tasman seas. A new paradoxostomatid genus, Glyphidocythere, is described to accommodate it and two other species yet to be formally described from the Banda Sea, eastern Indonesia. The genus is apparently restricted to the marine slope environment of low (less than 20°) southern latitudes. In the Coral and Tasman seas G. funafutiensis occurs within a narrow bathyal depth range (955m to 1754m) coincident with the Antarctic Intermediate Water.


This paper formally describes a new ostracod genus
Glyphidocythere based on disarticulated valves from the Quaternary and Recent of the western Pacific Ocean and the Recent of the Banda Sea, Indonesia. Chapman (1910) first recorded the new genus from Recent foraminifera ooze off western Funafuti at a depth of 1924m, but assigned his material to a new species of Pseudocythere: l? finufutiensis. The total number of specimens that Chapman collected is unknown, and few details regarding their depository were reported. Chapman did indicate, however, that the types were deposited at the British Museum of Natural History but he did not assign catalogue numbers to his material and apparently none were formally recorded at the museum. After a search through the collections at the museum (by M. Ayress) Chapman's (1910) type material from Funafuti was located and only one specimen, the holotype, of l? funufutiensis was present. The specimen has been examined for this study and although badly damaged is illustrated here. The species is more fully described below and shown to belong to a new genus (also described below) of the Paradoxostomatidae.
All of our material from the Coral Sea (Late Pleistocene and Recent) and the Tasman Sea (Early Pleistocene) is included within G. funufutiensis (Chapman), here designated the type species of Glyphidocythere gen. nov. Meyboom (1it.comm. 1991) has also shown us modem material from the Banda Sea, Indonesia which includes G. funufutiensis, and also two additional, as yet undescribed species of this genus.

MATERIAL
All records of G. funufutiensis and locality details are shown in Table 1.
Chapman's holotype is deposited and curated in the British Museum of Natural History No. 1911.11.7.50. Other material illustrated here is deposited at the National Museum of Victoria to which the catalogue numbers with prefix NMVP apply.

SYSTEMATIC DESCRIPTIONS
The following abbreviations are used: A = Adult, LV = left valve, RV = right valve.
Superfamily Cytheracea Baird, 1850 Family Paradoxostomatidae Brady & Norman,. 1889 Genus Glyphidocythere gen. nov. Type species: Pseudocytherefunufutiensis Chapman, 1910 here designated. Derivation of name: Greek, Glyphidos = knife, referring to the knife-like appearance of the species in this genus. Diagnosis: A large, extremely thin-shelled, paradoxostomatid genus with an acuminate anterior margin and a caudal process at or above mid-height. Carapace compressed with maximum inflation above mid-height. Dorsal margin straight to gently convex with a narrow low flange; ventral margin weakly biconvex. Inner lamella very wide with undulating inner margin medianly and a small vestibulum anteriorly; posteroventral vestibulum very narrow. Hinge lophodont with small anti-slip tooth in RV. Remarks: The acuminate anterior, undulating inner margin and four adductor muscle scars serve to distinguish this genus from superficially similar bythocytherid genera such as Pseudocythere, Ionesia and Baltraella.
Its four adductor muscle scars arranged in an oblique, closely spaced pattern, and the compressed thin shelled carapace are typical features of the Paradoxostomatidae. Within that family GZyphidocythere is most similar to Paradoxostoma and Machaerina. Those genera, particularly the former, display considerable variation in outline and some species are close in h s respect to Glyphidocythere. Paradoxostoma from the Red Sea for example (illustrated by Bonaduce et al., 1980, Pls 10, 12 & 13) has a wide range of lateral outline, of which P. subtile Bonatuce et al. is most similar to G. funafutiensis. I ? lizardensis Behrens, 1991, from the Great Barrier Reef, is also very similar in outline. However, Glyphidocythere differs from both Paradoxostoma asnd Machaerina, mainly in its undulating inner margin, its dorsal flange and in its very narrow postero-ventral vestibulum. Also the maximum inflation is often below midheight in Paradoxostoma not at or above mid-height as it is in Glyphidocythere. Paradoxostoma usually ranges in length between 0.50mm to 0.70mm with some species rarely 0.85mm (Van Morkhoven, 1963). Glyphidocythere is always longer than 0.75mm, with some specimens reaching a length of lmm. Only in Machaerina is this large size attained.
Glyphocythere shares with some species of Pseudocythere, Paracytherois and Paradoxostoma similar longitudinal striations on the external valve surface. This feature is not of taxonomic importance at the generic level, and, while its function is uncertain, it clearly has been developed convergently.

Glyphidocythere f u n u~t i e n s i s
(Chapman, 1910) (Pl. 1, figs 1-9, p1.2, figs 1-6, Fig. 1 All figures Glyphidocytherefunufufutiensis (Chapman). All dimensions are given as length x height in mm. bathyal water depths in the western Pacific are usually widespread and long-ranging   , 1990). This may well be a reflection of their fragile nature as well as a failure of some workers to examine the fine fraction of samples. Glyphidocythere is the first formally described paradoxostomatid genus of the deep-sea. An additional as yet undescribed genus of the same family possibly allied to Parucytherois, is also known to occur in the deep-sea environment worldwide (own unpublished data; Van Harten, lit. comm., 1991). Clearly the importance of t h s group in the deep-sea has been overlooked in previous studies.

Explanation of Plate 2
All figures G2yphidocytherefunufutiensis (Chapman). All dimensions are given as length x height in mm.