Potamonemus Cumberlidge and Clark, 1992

Cumberlidge, Neil, Mvogo Ndongo, Pierre A., Clark, Paul F. & Daniels, Savel R., 2019, A new genus for the freshwater crab Potamonemus asylos Cumberlidgeı 1993 ı (Brachyura: Potamoidea: Potamonautidae) from Cameroonı Central Africaı with a key to the genera of the Potamonautinae, Journal of Natural History 53 (11), pp. 659-676 : 667-674

publication ID

https://doi.org/ 10.1080/00222933.2019.1583390

DOI

https://doi.org/10.5281/zenodo.3680416

persistent identifier

https://treatment.plazi.org/id/03BB87C0-103F-393F-438E-FCC7FB0CFD7A

treatment provided by

Valdenar

scientific name

Potamonemus Cumberlidge and Clark, 1992
status

 

Potamonemus Cumberlidge and Clark, 1992 View in CoL

( Figures 2 View Figure 2 (a,b), 3(a,b), 4(b,c), 5(c – f), (h,i), 6(c – f), 7(b,c,e,f) and 8(b,c,e,f,h,i))

Potamonemus Cumberlidge and Clark, 1992: 49 View in CoL , figs 1 – 3, tables 1 – 2, pl. 1; Cumberlidge, 1999: 208 – 209, fig. 64D

Rediagnosis

Mandibular palp 2-segmented, lacking flap at junction between segments ( Figure 8 View Figure 8 (h,i)); G1 TA slim, curving outward, long (TA/SS 0.63), lacking setae, tapering to pointed tip ( Figure 7 View Figure 7 (b,c,e,f)); G2 TA distinctly shortened (TA/SS 0.13, Figure 8 View Figure 8 (b,c)).

Description

See Cumberlidge and Clark (1992) and Cumberlidge (1999). The carapace proportions of all known specimens of P. mambilorum have been recalculated in the present study (CW/FW 3.08, CW/FW 2.22, and CW/FW 0.96), and the relative lengths of the TAs of G1 and G2 of P. mambilorum (TA/SS of 0.63 and 0.13 respectively) are presented here for the first time.

Type species

Potamonemus mambilorum Cumberlidge and Clark, 1992 View in CoL , by original designation.

Type locality

Somié, Cameroon.

Species included

Potamonemus mambilorum and P. sachsi Cumberlidge, 1993 .

Distribution

Potamonemus is endemic to the rainforest zone of south-western Cameroon and southeastern Nigeria ( Cumberlidge 1993, 1999).

Remarks

The carapace proportions of all known specimens of P. sachsi View in CoL have been recalculated in the present study (see above), as have the relative lengths of the terminal articles of G1 and G2 of P. sachsi View in CoL , and these characters can be used to distinguish the two species of Potamonemus View in CoL from B. asylos View in CoL comb. nov.

Biogeography

The freshwater crab fauna of Cameroon is dominated by species of Sudanonautes View in CoL , and is most diverse in south-west Cameroon where there are two endemic genera ( Louisea View in CoL and Buea View in CoL gen. nov.), two species of Potamonemus View in CoL , and a single species of Potamonautes View in CoL (N. Cumberlidge unpub. data). Biogeographically, the affinities of the freshwater crabs of Cameroon lie with those of its neighbouring countries ( Nigeria, Central African Republic, Congo, Gabon, and Equatorial Guinea /Bioko) which occupy a forested part of Africa to the north of the Congo River that is bounded by the north-west coastline of Central Africa. The freshwater crab fauna of this part of Africa is dominated by species of Sudanonautes View in CoL and is remarkable for the almost complete absence of species Potamonautes (Cumberlidge 1999) View in CoL , which is the most species-rich and most widely distributed genus in sub-Saharan Africa (N. Cumberlidge, unpub. data). The freshwater crab fauna of Cameroon is unusually diverse (15 species in five genera), especially given the relatively small size of this Central African country (475,440 km 2). This species richness may be attributed to the abundance of stable lowland and highland equatorial forests and the numerous year-round water courses that are sustained over historical time by the high rainfall totals recorded for this part of Africa (Cumberlidge 1999; Mvogo Ndongo et al. 2017a; 2017b, 2017c, 2018) ( Table 1 View Table 1 ). The present study underlines the importance of Cameroon as a biodiversity hotspot because it has the highest number of freshwater crab genera in the whole of the African continent (Cumberlidge 1999; Daniels et al. 2015; Mvogo Ndongo et al. 2017a, 2017b, 2017c, 2018), and only Madagascar (with seven genera) is more diverse in the Afrotropical region as a whole ( Cumberlidge and Sternberg 2002; Cumberlidge et al. 2017).

Amended key to the genera of the African Potamonautinae View in CoL

1 The recognition of the new genus and the re-diagnosis of the reorganised Potamonemus View in CoL make it necessary to provide an amended key to the genera of the African Potamonautinae View in CoL .

1a Carapace frontal margin lined by small teeth or distinct granules; external angles of front marked by either sharp forward-pointing spine or small granule; triangular downward-pointing tooth beneath each external angle … ............ ........... Platythelphusa View in CoL

1b Carapace frontal margin smooth, external angles of front smooth (lacking spine, granule, or downward-pointing tooth) ................................................................................ 2

2a Carapace outline subhexagonal; outer margin of cheliped carpus with 2 or 3 sharp teeth; carpi and propodi of p2 – p5 with marginal spines................................ Erimetopus View in CoL

2b Carapace outline transversely oval; outer margin of carpus of cheliped smooth, lacking teeth; carpi and propodi of p2 – p5 smooth, lacking marginal spines .... 3 3a G1 TA curving inwards towards medial line................................................ Liberonautes View in CoL 3b G1 TA either straight or curving outwards away from medial line......................... 4

4a Third maxilliped exopod with long flagellum ................................................................... 5 4b Third maxilliped exopod lacking flagellum ........................................................................ 6

5a Intermediate tooth on anterolateral margin between exorbital and epibranchial teeth .......................................................................................................................... Sudanonautes View in CoL

5b No intermediate tooth on anterolateral margin between exorbital and epibran- chial teeth................................................................................................................ Potamonautes View in CoL

6a G1 TA long (TA/SS 0.63 – 0.86), curving outwards, ending in pointed tip; G2 TA much shorter (TA/SS 0.13 – 0.23) ............................................................................................. 7

6b G1 TA weakly S-shaped, tube-like, ending in rounded tip; G2 TA very long, flagellum- like (TA/SS 0.64).......................................................................................................................... Louisea View in CoL

7a G1 TA long (TA/SS 0.86), broadened in mid-section, with long marginal setae......... ........................................................................................................................................... Buea View in CoL gen. nov.

7b G1 TA short (TA/SS 0.63), slim along entire length, lacking long marginal setae..... ............................................................................................................................................. Potamonemus View in CoL

Kingdom

Animalia

Phylum

Arthropoda

Class

Malacostraca

Order

Decapoda

Family

Potamonautidae

Loc

Potamonemus Cumberlidge and Clark, 1992

Cumberlidge, Neil, Mvogo Ndongo, Pierre A., Clark, Paul F. & Daniels, Savel R. 2019
2019
Loc

Potamonemus

Cumberlidge N & Clark PF 1992: 49
1992
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