Nesonautes, Cumberlidge & Daniels, 2022

Cumberlidge, Neil & Daniels, Savel R., 2022, A new multilocus phylogeny reveals overlooked diversity in African freshwater crabs (Brachyura: Potamoidea): a major revision with new higher taxa and genera, Zoological Journal of the Linnean Society 194 (4), pp. 1268-1311 : 1291-1292

GENUS NESONAUTES GEN. NOV.

( FIGS 1B 2 , 4G–I, 9C; TABLES 1–3 )

Zoobank registration: urn:lsid:zoobank.org:act:558E16D5-0F1C-45CE-A1AE-F1F2438C5758 .

Thelphusa A. Milne-Edwards, 1869: 185 , pl. 9, fig. 4, fig. 4a–b; Greef, 1882: 37; 1884: 54; A. Milne-Edwards, 1886: 150; 1887: 130; Ozorio, 1887: 221; 1889: 129, 132; 1892: 199; 1905: 149.

Telphusa Brito-Capello, 1871 : pl. 2, fig. 12 [not A. Milne-Edwards].

Potamon (Potamonautes) Ortmann, 1897: 304 , 308; Rathbun, 1900: 283; 1904: pl. 14, fig. 10; 1905: 168–169; De Man, 1914: 135.

Potamon Chace, 1942: 216 .

Potamonautes (Platypotamonautes) Bott, 1955: 229 , 235, pl. XXX: figs la–d, 11 (only Po. (Pl.) margaritarius = N. margaritarius comb. nov.; not Po. (Pl.) ecorssei = Occidensonautes ecorssei comb. nov., Po. (Pl.) platynotus = Arcopotamonautes platynotus comb. nov., Po. (Pl.) pilosus = Rotundopotamonautes pilosus comb. nov., Potamonautes (Rotundopotamonautes) neumanni = Rotundopotamonautes neumanni comb. nov.

Potamonautes margaritarius Balss, 1914: 102 ; Ng et al., 2008: 171; Cumberlidge, 2008: 72, 77, tab. 1; 2011: 79, 82–83, tabs 6.1, 6.3; Daniels & Klaus, 2018: 119–127, figs 1–3, tab 1; Cumberlidge & Daniels, 2018: 289–295, figs 1–3.

Diagnosis: G1 TA long (TA/SA 0.45–0.48 length of G1 SA); G1 TA angled at 45° to the longitudinal axis of G1 SA; G1 TA widened in the middle (dorsal fold higher than ventral fold); G1 TA terminating in highly upcurved tip ( Fig. 4G –I ); carapace flattened ( CH /FW 1.0); anterolateral margin behind epibranchial tooth either finely toothed or granular; third maxilliped ischium smooth, lacking vertical suture.

Etymology: The genus name is a combination of the Greek νήσος, island, and ναύτες seamen, “- nautes ” being a common suffix for freshwater crabs. This to recognize that this genus of freshwater crabs is endemic to São Tomé Island. The gender is masculine.

Type species: Thelphusa margaritaria A. Milne- Edwards, 1869, by present designation.

Species included: Nesonautes margaritarius (A. Milne- Edwards, 1869) comb. nov. and Nesonautes saotome ( Cumberlidge & Daniels, 2018) comb. nov.

Distribution: Nesonautes species are endemic to São Tomé Island ( São Tomé and Príncipe) ( Daniels & Klaus, 2018; Cumberlidge & Daniels, 2018; Fig. 9C ).

Remarks: Nesonautes is established here to accommodate two species of freshwater crabs that are endemic to São Tomé Island, which were previously considered to be species of Potamonautes s.l. ( Bott, 1955; Cumberlidge & Daniels, 2018). A new genus is necessary because these two species form a unique genetic lineage separate from the large clade for Potamonautini ( Fig. 1B 3 ) and the clade formed by Erimetopus , Longipotamonautes and Occidensonautes ( Daniels & Klaus, 2018) . Because neither of the included species is the type species of a genus or a subgenus, a new genus name is provided here.

Bott (1955) included N. margaritarius (as P. margaritarius ) as one of five species in his subgenus Potamonautes (Platypotamonautes) (together with Potamonautes ecorssei , Potamonautes platynotus , Potamonautes pilosus and Potamonautes neumanni ). However, subgenus P. (Platypotamonautes) is not monophyletic because the species he included were found here to belong to four different phylogenetic lineages ( Daniels et al., 2006, 2015; Fig. 1 ) and it is therefore not recognized here. Potamonautes margaritarius i s t h u s a s s i g n e d t o N e s o n a u t e s, P. e c o rs s e i i s transferred to Occidensonautes . Potamonautes platynotus is moved here to Arcopotamonautes and P. pilosus and P. neumanni are now assigned to Rotundopotamonautes .

Figures

Figure 1. A, maximum clade credibility tree of the Afrotropical freshwater crab fauna based on four DNA loci with support values (posterior probabilities and bootstrap values of the ML analyses) with a geological timescale below the tree topology. Posterior probabilities> 0.95 pP (*above branch) and bootstrap values> 75% (* below branch) were regarded as statistically supported and are shown on the tree topology. Clade A, Liberonautinae, clade B, Potamonautinae, clade B1, Maritimonautini, clade B2, Erimetopini, clade B3, Potamonautini. B, detail of the maximum clade credibility tree of the Afrotropical freshwater crab fauna showing Clade B3 Potamonautini with the species included in the five genera within the tribe: Arcopotamonautes (B3[1]), Lirrangopotamonautes (B3[2]), Platythelphusa (B3[3]), Potamonautes s.s. (B3[4]) and Rotundopotamonautes (B3[5]).

Figure 3. Gonopods 1 and 2 of four genera in Liberonautinae. A–C, Buea asylos (Cumberlidge et al., 2019: fig. 7a, d; 8a); D–F, Potamonemus mambilorum (Cumberlidge et al., 2019: fig. 7b, e; 8b); G–I, Sudanonautes floweri; J–L, Louisea balssi (Mvogo Ndongo et al., 2018: fig. 5a–c, © Magnolia Press, reproduced with permission from the copyright holder). A, D, G, J, left G1 ventral view; B, E, H, K, left G1 dorsal view; C, F, I, L, left G2 ventral view. Scale bar: A, B, D, E, G, H, J, K = 2.0 mm, C, F, I, L = 1.8 mm.

Figure 4. Gonopods 1 and 2 of the four genera in Erimetopini. A–C, Erimetopus vandenbrandeni; D–F, Longipotamonautes ballayi; G–I, Nesonautes margaritarius; J–L, Occidensonautes ecorssei. Scale bar: A–L = 2.0 mm.

Figure 9. Maps showing the distributional ranges of the four genera of Erimetopini (A) Erimetopus, (B) Longipotamonautes, (C) Nesonautes and (D) Occidensonautes.

Figure 2. Liberonautinae. Gonopods 1 and 2 of Liberonautes latidactylus, NMU9.V.2005B (CW 72, CL 47.2, CH 20.5, FW 19.3 mm) Guinea, West Africa. A, left G1 ventral view; (B) left G1 dorsal view; (C) left G2 ventral view. Scale bar: A, B = 2.8 mm, C = 1.8 mm.