BASEODISCUS UNICOLOR STIASNY-WIJNHOFF, 1925 (FIG. 2L) Baseodiscus unicolor Stiasny-Wijnhoff, 1925: 103, textfig.3, pl. V, fig.7 (Spanish Water, Curaçao); Schwartz, 2009: 68, figs 22E, 23A–F (Cat Cay, Belize); Kvist et al., 2014: 291, in part (Bocas del Toro, Panama). Sequences: KF935284, 18S (1770 bp); KF935340, 28S (2061 bp); KF935396, H3 (238 bp); KF935451, 16S (506 bp); KF935505, COI (658 bp); determined by Kvist et al. (2014) and deposited in GenBank as isolate SK68, based on MCZ DNA 106302, derived from a specimen found in the Bocas del Toro Archipelago, Panama, ~ 17 m depth, 18 March 2011, collected and identified by G. Giribet and deposited in MCZ under catalogue number IZ-135323. EF124865, 16S (539 bp), from isolate 694, collected and identified by M. Schwartz ‘from an extensive field of Porites sp. coral rubble around the edges of a mangrove channel at a depth of 0.5 m’ at Cat Cay, Belize (Schwartz, 2009: 68). External features: Body brown to reddish brown in colour, without any distinctive pattern (Fig. 2L) (cf. Schwartz, 2009: 69). Distribution: Spanish Water, Curaçao (type locality; S t i a s n y - W i j n h o f f, 1 9 2 5); C a t C a y, B e l i z e (Schwartz, 2009); Manawar Cay, Bocas del Toro Archipelago, Panama (Kvist et al., 2014). Remarks: We regard the two specimens analysed to represent B. unicolor. Stiasny-Wijnhoff (1925: 103) described the body colour as ‘a dark reddish brown without any markings’ after ‘preservation with sublimate and alcool [sic]’. There appear to be two distinct species along the Caribbean coasts of Central and South America, both having brownish body colour without any distinctive patterning. They seem to differ in the shade/depth of the brown colour; the dark-brown form should be referred to by the name B. unicolor in reference to Stiasny-Wijnhoff ’s (1925) original description. For the pale-coloured form, we establish B. giribeti; see Remarks for that species (following).

Published as part of Kajihara, Hiroshi, Abukawa, Shushi & Chernyshev, Alexei V., 2022, Exploring the basal topology of the heteronemertean tree of life: establishment of a new family, along with turbotaxonomy of Valenciniidae (Nemertea: Pilidiophora: Heteronemertea), pp. 503-548 in Zoological Journal of the Linnean Society 196 on page 527, DOI: 10.1093/zoolinnean/zlac015, http://zenodo.org/record/7037958