Abyssocythere Benson, 1971

Brandão, Simone N., Stuhlmann, Annalena, Vital, Helenice & Brandt, Angelika, 2016, Biogeography of Abyssocythere and Dutoitella (Ostracoda), with descriptions of three new species, Zootaxa 4139 (3), pp. 391-418 : 394-399

Genus Abyssocythere Benson, 1971

Type species. Abyssocythere casca Benson, 1971 (by original designation)

Additional valid species. (listed by original binomina in alphabetical order of the species epithet) (Brandão et al. 2015; Kempf, 1986, 1988, 1994, 1995, 1996a, b, 2002, 2004, 2008a, b) Abyssocythere atlantica Benson, 1971 ; Abyssocythere australis Benson, 1971 ; Abyssocythere bilobata Colin, 1987 ; Abyssocythere braziliensis Benson in Benson & Peypouquet, 1983 ; Abyssocythere carpathica Pokorny, 1973 ; Abyssocythere casca Benson, 1971 ; Paleoabyssocythere cenozoica Benson, 1977 ; Cythereis contramaestrensis Luebimova & Sanchez, 1974 ; Bradleya (Quasibradleya) diagrenona Guernet, 1985 ; Abyssocythere japonica Benson, 1971 ; Abyssocythere pannucea Benson, 1971 ; Abyssocythere paratrinidadensis Boomer, 1999 ; Abyssocythere regalis Zhao in Wang et al. 1985 ; Abyssocythere scotti Yasuhara et al., 2015 and Abyssocythere bensoni sp. nov.

Additional unaccepted species (previously assigned to Abyssocythere , but currently accepted in other genera). (Brandão et al. 2015; Kempf, 1986, 1988, 1994, 1995, 1996a, b, 2002, 2004, 2008a, b) Abyssocythere squalidentata (Brady, 1880) nomen dubium according to Benson (1971); Abyssocythere antarctica (Neale, 1967) accepted as Austrotrachyleberis antarctica (Neale, 1967) ; Abyssocythere trinidadensis (Bold, 1957) accepted as Paleoabyssocythere trinidadensis (Bold, 1957) . Abyssocythere sulcatoperforata (Brady, 1880) (most probably a typographical mistake for Abyssocythereis sulcatoperforata ) accepted as Protocythere sulcatoperforata (Brady, 1880) (new combination by Yasuhara et al., 2015).

Abyssocythere bensoni sp. nov. ( Figures 1 , 5 , 6 , Table 1)

Diagnosis. An Abyssocythere species with sub-quadrate to sub-ovate outline in lateral view. Anterior and posterior cardinal angle with similar height. Lateral surface relatively level. Long spines present on anterior margin. Secondary reticulation conspicuous and rounded. Sub-central tubercle relatively small, but prominent.

Derivation of name. In honor of the late Richard Benson for his outstanding contributions to deep-sea research, paleontology and ostracodology.

Material. Holotype: 1 Subrecent right valve, ZMH K- 44856. Paratype (type locality): 1 Subrecent right valve, ZMH K- 44857.

Stratigraphic and geographical occurrence. (locality 3 in Fig. 1 and Tab. 1). Quaternary. Scotia Sea, Southern Ocean 3631 to 3637m depth (only known from the type locality).

Type locality. Subrecent. ANDEEP I cruise, PS 61, ANT-XIX/3, German Research Vessel Polarstern, station 129-2, Scotia Sea, Southern Ocean, 23.02.2002, supranet of the epibenthic sledge trawled from 59°52.55'S, 59°57.26'W, 3631m to 59°52.20'S, 59°58.63'W, 3637 m.

Description. [Morphological terminology follows Benson 1971]. External view ( Fig. 5 ). Lateral outline subquadrate to sub-ovate, anterior cardinal angle seems just slightly higher than posterior cardinal angle, but from the internal view, the anterior appears higher than the posterior, but the dorsal muri obscure this in external view. Reticulation well developed and finely sculptured with complete primary mural nets and secondary muri. Secondary ornamentation conspicuous, with evenly rounded pits on the entire lateral surface. Muscle-scar node a small, smooth bulbous prominence. Several conspicuous intramural pores present on valve surface. Anterior margin with reticulated rim, venter not rimmed and fairly straight, posterior margin rounded with several stubby A, C–F, holotype (ZMH K-44856); B, paratype (ZMH K-44857). A–B, entire right valves. C–G, details of valve ornamentation, C, postero-ventral region. D, antero-ventral region. E, detail of secondary ornamentation. F, secondary ornamentation and pore with seta.

A, anterior hinge element of D. B, posterior hinge element of D. C, adductor and frontal muscle scars of D. D, entire right valve.

spines, and not rimmed. Levatum (anterior reticulate complex) evenly reticulate, joining the rest of the reticulum without a noticeable change in relief. Ventrolateral ridge comprised of five rectangular fossae joined ventrally by a weak ventrolateral carina. Postsulcular node more conspicuous than other three (more posterior) intramural pore nodes. Very conspicuous, slightly sinuous gamos ridge running from postsulcular node to the posterodorsal bulla. Anterodorsal “ear” not conspicuous on RV. From the four mural processes of the dorsal bullae series, only A, B and the posterodorsal bulla are conspicuous. Mural process is blade-like, but very small. Shape of mural processes A and posterodorsal bulla also blade like, but large. Shape of mural process B ‘spine-like’, pointed and elongated. Additional mural process (pointed in shape) present posterior to posterodorsal bulla. Posterior cardinal angle rounded and inconspicuous, hidden by the additional mural process.

Internal view ( Fig. 6 ). Outline sub-ovate, anterior considerably higher than posterior. Zone of concrescence narrow. Frontal scar possibly V-shaped (internal surface not very well preserved). There are four complete adductor muscle scars. Hinge merodont, with crenulate anterior and posterior elements. In right valve, anterior element has three large and two small crenulae; and posterior element has four large and two small crenulae.

Measurements. HOLOTYPE (ZMH K-44856), adult RV length 0.87mm; height 0.52mm. PARATYPE (ZMH K-44857), adult RV length 1.07mm; height 0.63mm.

Remarks. The lateral outline of Abyssocythere bensoni sp. nov. is more sub-quadrate, less elongate, and the anterior and posterior cardinal angles are more similar in height than Abyssocythere australis , Abyssocythere braziliensis , Abyssocythere casca , Abyssocythere cenozoica , Abyssocythere diagrenona , Abyssocythere japonica , Abyssocythere pannucea and Abyssocythere scotti . Additionally, A. australis , A. braziliensis , A. casca , A.

cenozoica , A. diagrenona and Abyssocythere paratrinidadensis show more conspicuously elevated muri and dorsal bullae than the new species. Abyssocythere bensoni sp. nov. shows an evenly contoured lateral surface, while in Abyssocythere atlantica and Abyssocythere japonica the surface is sinuous due to the elevation of the ventrolateral area. The anterior rim of the new species is narrower and less conspicuous than A. japonica . Additionally, A. bensoni sp. nov. differs from A. japonica in the gamos ridge, which in the latter joins two other prominent vertical posterodorsal ridges, while in the former it is isolated from the other two ridges. Finally, A. bensoni sp. nov. differs from A. atlantica , A. japonica and A. pannucea Benson, 1971 in its slightly sinuous gamos ridge, which in the last three species “bends sharply at least once throughout its extent” (Benson, 1971).

Figures

FIGURE 1. Geographical distribution of Abyssocythere Benson, 1971 in the different geological epochs or stages (for a complete list of references used for this Figure see Supplementary material 1).

FIGURE 5. External views of the valves of the holotype and paratype of Abyssocythere bensoni sp. nov. Type locality. Subrecent. Southern Ocean, Scotia Sea, German Research Vessel Polarstern, ANDEEP I cruise, PS 61, ANT- XIX / 3, station 129 - 2, 23.02. 2002, supranet of the epibenthic sledge trawled from 59 ° 52.55 ' S, 59 ° 57.26 ' W, 3631 m to 59 ° 52.20 ' S, 59 ° 58.63 ' W, 3637 m.

FIGURE 6. Internal view of the holotype of Abyssocythere bensoni sp. nov. (ZMH K- 44856). Type locality. Subrecent. Southern Ocean, Scotia Sea, German Research Vessel Polarstern, ANDEEP I cruise, PS 61, ANT- XIX / 3, station 129 - 2, 23.02. 2002, supranet of the epibenthic sledge trawled from 59 ° 52.55 ' S, 59 ° 57.26 ' W, 3631 m to 59 ° 52.20 ' S, 59 ° 58.63 ' W, 3637 m.