GENUS OCCIDENSONAUTES GEN. NOV.

(FIGS 1B 2, 4J–L, 9D; TABLES 1–3)

Zoobank registration: urn:lsid:zoobank.org:act: 86B558AA-36DF-464F-AEAA-266D9FFEA94A.

Potamon (Potamonautes) Marchand, 1902: 334–342, pls 1, 3, figs 2–6; Rathbun, 1905: 180; Roux, 1935: 32–34.

Potamon Chace, 1942: 210.

Potamonautes (Platypotamonautes) Bott, 1955: 229; 1959: 1002–1004, fig. 4.

Potamonautes (Isopotamonautes) Bott, 1955: 247; 1959: 1004; 1970: 340–341, pl. 1.

Potamonautes Cumberlidge, 1999: 129–130; Ng et al., 2008: 170; DuriŠ & Koch, 2010: 220.

Diagnosis: Exorbital tooth small, low; epibranchial tooth small but distinct; anterolateral margin between exorbital, epibranchial teeth lacking intermediate tooth; anterolateral margin posterior to epibranchial tooth raised, lacking teeth; episternal sulci S4/E4, S5/E5, S6/E6 all clearly visible; S7/E7 lacking visible groove. Posterior margin of carapace ~1/2 as wide as CW; third maxilliped ischium smooth (or with faint vertical sulcus); S3/4 deep, V-shaped, midpoint meeting anterior margin of sterno-pleonal cavity; G1 TA short (~1/3 as long as G1 SA), tip pointed (Fig. 4J–L).

Etymology: The genus name is a combination of Latin occidens, west and “ nautes ”, Ancient Greek for seamen, a common suffix for African freshwater crabs, in recognition that this genus is endemic to West Africa. The gender is masculine.

Type species: Potamon (Potamonautes) ecorssei, Marchand, 1902, by present designation.

S p e c i e s i n c l u d e d: O c c i d e n s o n a u t e s e c o r s s e i (Marchand, 1902) comb. nov., O. lipjkei (DuriŠ & Koch, 2010) comb. nov., O. senegalensis (Bott, 1970) comb. nov. and O. triangulus (Bott, 1959) comb. nov.

Distribution: Occidensonautes is endemic to West Africa from Senegal to the Niger River Basin in Nigeria (Cumberlidge, 1999; DuriŠ & Koch, 2010). O. ecorssei is the species with the widest distributional range and is found from the Senegal River Basin (Senegal) to the Niger River Basin in Nigeria, Occidensonautes lipjkei and Occidensonautes senegalensis are both endemic to Senegal, while Occidensonautes triangulus is endemic to Ghana (Fig. 9D).

Remarks: All four of these West African species were previously assigned to Potamonautes s.l. DNA data are only available for O. ecorssei, and so the other three species are included here based on shared morphological characters that conform to the above generic diagnosis. A new genus has been established, because the phylogeny indicates that O. ecorssei represents a unique genetic lineage sister to Longipotamonautes (Daniels et al., 2015: fig. 1; Fig. 1B 2), but separate from the clades for Potamonautini (Fig. 1B 3) and Maritimonautini (Fig. 1B1). In addition, a new genus is necessary because no published genuslevel name is available and none of the included species is the type species of either a genus or a subgenus. The earlier taxonomic assignment by Bott (1955, 1959) of O. ecorssei and O. triangulus to Potamonautes (Platypotamonautes) Bott, 1955 is not recognized here because this subgenus as configured by Bott (1955) is not monophyletic according to the phylogenetic relationships presented here (Fig. 1). For example, Po.ecorssei was one of five species included by Bott (1955) in Po. (Platypotamonautes) a paraphyletic assemblage that groups together species from four different phylogenetic lineages within the Potamonautinae (Daniels et al., 2006, 2015; Fig. 1). For this reason, Po. ecorssei is moved to Occidensonautes (Fig. 1B 2), Po. margaritarius is assigned to Nesonautes (Fig. 1B 2), Po. platynotus is transferred to Arcopotamonautes (Fig. 1B 3 [1]) and Po. pilosus and Po. neumanni are moved to Rotundopotamonautes (Fig. 1B 3 [5]).