Oswaldella rigida Peña Cantero et al., 1997: 373–376, figures 10, 15C; Peña Cantero and Vervoort, 1998: 36; Peña Cantero and García Carrascosa, 1999: 214; Peña Cantero and Marques, 1999: 85.
Schizotricha antarctica: Vanhöffen, 1910: 336, figure 48.
Remarks. Oswaldella rigida is well characterized by the branched stems, the angle of 70–90 ° formed between the cauline apophyses and the stem, the absence of a node between the cauline apophyses and the hydrocladia, the shape of the hydrotheca, provided with an adcauline elevation, and the presence of two axillary nematophores on the cauline apophyses (cf. table 1).
Ecology and distribution. Oswaldella rigida is a shelf species, having been found at depths from 80 to 830 m on muddy and rocky bottoms (Peña Cantero et al., 1997).
Oswaldella rigida appears to have a circum-Antarctic distribution (Peña Cantero et al., 1997). It is known from the Davis Sea (Vanhöffen, 1910) in East Antarctica, and at the east coast of the Weddell Sea (Peña Cantero et al., 1997) in West Antarctica.