Australicythere, BENSON, 1964

Brandão, Simone N., Saeedi, Hanieh & Brandt, Angelika, 2022, Macroecology of Southern Ocean benthic Ostracoda (Crustacea) from the continental margin and abyss, Zoological Journal of the Linnean Society 194, pp. 226-255 : 239

GENUS AUSTRALICYTHERE BENSON, 1964

( FIG. 4B )

Australicythere sp. ( Fig. 2A )

Remarks: Australicythere sp. is similar to Australicythere polylyca ( Müller, 1908) , but the original description of the last species contained only simple sketches ( Müller, 1908: pls 12.1, 12.5, 12.6), because no SEM was available at that time. The type material has not been re-investigated or re-illustrated since then and, consequently, the morphology of the species remains unknown. Subsequent authors recorded specimens identified as A. polylyca from 93 locations of the continental shelf of Antarctica (17–464 m) in the Atlantic, Pacific and Indian sectors of the SO ( Brandão, 2012; Brandão & Dingle, 2014; Riehl et al., 2020). However, all these records, and consequently the putatively wide geographical distribution range of A. polylyca , need to be taken with care, because SEM photos and illustrations of the specimens studied from different authors are distinct from the original illustrations and sometimes also distinct from each other. For example, the recent specimen from the Gauss station (type locality, Indian Sector of the SO) has a subrectangular outline, with subparallel dorsal and ventral margins and wide marginal rim ( Müller, 1908: pl. 17.1). The specimen from the Taylor Formation (Pleistocene, Ross Island, Pacific Sector of the SO) has a wide marginal rim, but sinuous dorsal margin and dorsolateral ribs ( Briggs, 1979: fig. 2.2). The specimen from McMurdo Sound (Recent, Sulzberger Bay, Pacific Sector of the SO) has a subrectangular outline, but with a narrow marginal rim ( Benson, 1964: pl. 4.2). The specimens from the Antarctic Peninsula have a subtriangular outline, with sinuous dorsal margin ( Hartmann, 1986: pl. 3.4).

Therefore, we herein prefer to leave the specimens of Australicythere in open nomenclature, rather than adding even more confusion to a taxon that is already in need of a taxonomic review. The genus Australicythere is recorded for the first time in the continental slope of Antarctica and adjacent abyssal plain (3631 m), because all previous records were from the continental shelf (17–464 m).

Figures

Figure 2. Selected ostracod species from the Atlantic Sector of the Southern Ocean, collected during the EASIZ II (PS 48/ANT XV-3) and ANDEEP I, II and III cruises (PS 61/ANT XIX-3, PS 67/ANTXXII-3, PS 67/ANTXXII-4) on board the RV Polarstern. A, Australicythere sp. (Eastern Weddell Sea, ANDEEP II, station 132, 2084 m); B, Macroscapha opaca Maddocks, 1990 (Eastern Weddell Sea, EASIZ II, station 133, 2043m); C, Cytherella rwhatleyi Brandão, 2008a (holotype, Eastern Weddell Sea, station 89, EASIZ II, 1639 m); D, Ayressoleberis bathymarina (Ayress, 1993) (Western Scotia Sea, ANDEEP II, station 141-10, 2369 m); E, Bythopussella brandtae Brandão, 2008b (paratype, Western Weddell Sea, ANDEEP II, station 133-3, 1123 m); F, Legitimocythere sp. (Western Weddell Sea, EASIZ II, station 272, 2076 m); G, Neonesidea keyseri Brandão, 2008 (Eastern Scotia Sea, ANDEEP II, station 140-8, 2965 m) (this species belongs to a new genus, which was not named due to the few specimens available); H, Poseidonamicus tainae Brandão inBrandão & Päplow,2011 (Western Scotia Sea,ANDEEP I, station 41-3, 2380 m); I, Bythocypris malyutinae Brandão, 2008b (holotype, Weddell Sea, ANDEEP III, station 102-13, 4818 m); J, Krithidae sp. (WesternWeddell Sea, EASIZ II, station 272, 2076 m); K, Henryhowella sp. (Western Scotia Sea, ANDEEP I, station 42-2, 3681 m); L, Pseudobosquetina nobilis Jellinek et al., 2006 (Western Weddell Sea, ANDEEP II, station 134-4, 4059 m); M, Retibythere (Bathybythere) sp. nov. (Western Scotia Sea, ANDEEP I, station 131-3, 3055 m).

Figure 4. Relative abundance of selected ostracod genera in relation to water depth in the Atlantic Sector of the Southern Ocean. Estimates based on samples collected during the EASIZ II (PS 48/ANT XV-3) and ANDEEP I, II and III cruises (PS 61/ANT XIX-3, PS 67/ANTXXII-3, PS 67/ANTXXII-4) on board the RV Polarstern.