(!) Rhysida H.C. Wood, 1862

Figs 106–109

Type species. Branchiostoma lithobioides Newport, 1845 (by subsequent designation of Attems 1930) .

Diagnosis. Median tooth of labrum well developed. Forcipular tooth-plates present, trochantero-prefemur with well-developed process (Fig. 106). Tergites never with longitudinal keels (except for median one in a few species). Sternites with incomplete paramedian sutures (in some species much shortened, sometimes also with median and lateral depressions of various sizes/shapes. LBS 7 with spiracles, the latter with atrium (Fig. 108). Legs with tarsal spur(s), legs 1 without prefemoral spur. Coxopleural process (Fig. 109) ranging from short to very long and much enlarged (figs 4F and 9F in Siriwut et al. 2018, respectively), with spines (at least with apical ones). Prefemur of the ultimate leg with spines (Fig. 107), more rarely (for example in R. celeris) without them; pronounced corner spine absent (in some species 1(2) spines at its place, Fig. 107). Ultimate pretarsus well-developed, with accessory spines.

Number of species. 36 (Joshi et al. 2020).

Sexual dimorphism. Unknown.

Remarks. Treated as a genus in Edgecombe & Bonato (2011: 402), Vahtera et al. (2012a: 7, 2012b: 238, 2013: 578), Chagas-Jr (2013: 17), Schileyko (2014: 182), Schileyko & Stoev (2016: 255), Siriwut et al. (2018: 1005); Joshi et al. (2020); the latter work is the most recent account on this genus (see also Remarks to Alluropus below). In 2013 Chagas-Jr synonymized seven species of Rhysida (namely R. caripensis, R. guayanica, R. maritima, R. monaguensis, R. neoesparanta, R. porlamarensis and R. sucupaensis) described by González-Sponga (2002) to R. celeris . Five new species were described from India by Joshi et al. (2020).

We re-investigated a dozen specimens of R. celeris from Peru (Rc 6685) and Brazil (Rc 7272), R. immarginata (Porat, 1876) from Papua New Guinea (Rc 7091), R. longipes (Newport, 1845) from Cambodia (Rc 7003) and Peru (Rc 6683), R. lithobioides (Newport, 1845) from Sumatra (Rc 7232). All the studied specimens showed a total absence of both a corner spine of the ultimate legs (Fig. 107) and a prefemoral spur on legs 1.