Australicythere Benson 1964

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).