Potamonautes raybouldi Cumberlidge & Vannini, 2004

Reed, Sadie K. & Cumberlidge, Neil, 2006, Brachyura: Potamoidea: Potamonautidae, Platythelphusidae, Deckeniidae (), Zootaxa 1262 (1), pp. 1-139 : 1-139

11. Potamonautes raybouldi Cumberlidge & Vannini, 2004 (Figs. 104–112, 165–166, 183, plate XI)

Potamonautes raybouldi Cumberlidge & Vannini, 2004: 683–689 , Figs. 1–2.

Type material examined: TANZANIA: Adult male holotype (cw 55.7 mm) from waterfilled tree hole in forest 500 m asl, near Zigi , 9 km from Amani , East Usambara mountains , iv.1966 (J. N. Raybould) ( NMU KMH 11486); two adult male paratypes (cws 39.6, 40.5 mm) (from water­filled tree holes in forest 500 m asl, near Zigi, 9 km from Amani, East Usambara mountains , iv.1966 (J. N. Raybould) ( NMU TRW1966 .A.2); East Usambara mountains near Zigi, 9 km from Amani, from water­filled tree holes in forest 500 m asl, subadult female (cw 36.9 mm), subadult male (cw 29.6 mm) vi.1966 (J. N. Raybould) ( NMU TRW1966 .B.2); adult male (cw 46.5 mm), subadult female (cw 36.2 mm), in water­filled tree holes in forest near Amani, East Usambara mountains, iv.1966 (J. N. Raybould) ( NMU TRW1966.11 ) .

Additional material. For a complete account of other material from Tanzania and Kenya, see Cumberlidge & Vannini (2004).

Diagnosis. Postfrontal crest sharp­edged, spanning entire carapace; exorbital tooth large, sharp, directed forward; epibranchial tooth reduced to small granule; anterolateral margin between exorbital, epibranchial teeth smooth; anterolateral margin posterior to epibranchial teeth raised, granulated, end curving inward over carapace surface; carapace highly arched (ch/fw 1.5–1.7); suborbital margin smooth raised; suborbital, subhepatic regions of carapace sidewalls with fields of large granules, pterygostomial region smooth; thoracic sternal sulcus s3/s4 complete, deep, v­shaped, not meeting anterior margin of sternoabdominal cavity; episternal sulci s4/e4, s5/e5, s6/e6 s7/e7 all complete; second carpal tooth of carpus of cheliped pointed, large, half size of first tooth, directed at 70°–90° angle to first tooth; tip of terminal article of gonopod 1 curving sharply upward; terminal article distinctly widened in middle by high medial fold; distal margin of subterminal segment concave, medial margin much wider than lateral margin, forming rounded medial shoul­ der; base of terminal article at dorsal membrane concave; dorsal membrane wide on lateral margin tapering to point at medial margin; inner outer surfaces of merus, carpus, of palm of propodus of cheliped all with conspicuous reticulated rust­red pattern over cream background.

Size. The size range of adult males and females begins at around cw 39 mm.

Type locality. Zigi , 9 km from Amani, East Usambara Mountains, Tanzania .

Distribution. Kenya and Tanzania.

Remarks. Cumberlidge & Vannini (2004) provided detailed comparisons to other species of Potamonautes , as well as notes on the distribution, natural history and color of the crab.

Natural history and conservation status. Potamonautes raybouldi occurs in waterfilled tree holes in deciduous forests ( Bayliss 2002; Cumberlidge & Vannini 2004). Bayliss (2002) provided a detailed ecological study of the habitat of this species. A discussion of freshwater crabs that live in phytotelmic habitats is provided by Cumberlidge et al. (2005). The conservation status of P. raybouldi is categorized as vulnerable (VU) ( Table 4) because it has a narrow range of occurrence and a restricted area of occupancy that are both below the thresholds for vulnerable (VU) ( IUCN 2004). It is difficult to estimate the population status and trends of this species but its population is estimated to be declining based on its specialized habitat requirements (water­filled tree holes) and on the increasing habitat disturbance from deforestation associated with growing human populations in the region.