Occidensonautes, Cumberlidge & Daniels, 2022

GENUS OCCIDENSONAUTES View in CoL GEN. NOV.

( FIGS 1B View Figure 1 2 View Figure , 4J–L, 9D; TABLES 1–3 View Table 1 View Table 2 View Table 3 )

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

Potamon Chace, 1942: 210 View in CoL .

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 View in CoL ; 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 View Figure 4 ).

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 View Figure 9 ).

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 View Figure 1 2 View Figure ), but separate from the clades for Potamonautini ( Fig. 1B View Figure 1 3 View Figure 3 ) and Maritimonautini ( Fig. 1B1 View Figure 1 ). 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 View Figure 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 View Figure 1 ). For this reason, Po. ecorssei is moved to Occidensonautes ( Fig. 1B View Figure 1 2 View Figure ), Po. margaritarius is assigned to Nesonautes ( Fig. 1B View Figure 1 2 View Figure ), Po. platynotus is transferred to Arcopotamonautes ( Fig. 1B View Figure 1 3 View Figure 3 [1]) and Po. pilosus and Po. neumanni are moved to Rotundopotamonautes ( Fig. 1B View Figure 1 3 View Figure 3 [5]).