Zootaxa 1981: 29–42 (2009) ISSN 1175-5326 (print edition) www.mapress.com/zootaxa/ Article ZOOTAXA Copyright © 2009 · Magnolia Press ISSN1175-5334(online edition) A revision of the freshwater crabs of Mt Kenya and the Aberdare Mountains, Kenya, East Africa (Brachyura: Potamoidea: Potamonautidae). NEIL CUMBERLIDGE Department of Biology, Northern Michigan University, Marquette, Michigan 49855-5301, USA. E-mail: [email protected] Abstract The taxonomy of the freshwater crabs of Mt Kenya and the Aberdare Mountains in central Kenya, East Africa is revised based on a large collection of previously unreported material. Three species belonging to the genus Potamonautes MacLeay, 1838 (Potamonautidae Bott, 1970) are recognized from the region and redescribed. Potamonautes jeanneli (Bouvier, 1921) and P. odhneri (Colosi, 1924) are both resurrected from synonymy and P. alluaudi (Bouvier, 1921) is recognized as a valid species rather than as a subspecies of P. suprasulcatus (Hilgendorf, 1898). All three species are endemic to the Central Province, Kenya. Key words: Crustacea, Brachyura, Potamoidea, Potamonautidae, Potamonautes, freshwater crab, taxonomy, Mt Kenya, Aberdare Mountains, Kenya, East Africa Introduction European and American expeditions to Mt Kenya and the Aberdare Mountains in Kenya in East Africa in the early 20th Century led to the description of three species of freshwater crabs from this region (Bouvier 1921, Colosi 1924). These included two species from Mt Kenya itself, Potamon (Geothelphusa) jeanneli Bouvier, 1921, and Potamon (Potamonautes) odhneri Colosi, 1924, and Potamon (Potamonautes) alluaudi Bouvier, 1921, from Nairobi Forest south of Mt Kenya. These three species were also recognized by Balss (1929) and Chace (1942), but the major taxonomic revision of Bott (1955) did not consider any of them to be valid. For example, Bott (1955) treated P. (G.) alluaudi as Potamonautes (Arcopotamonautes) suprasulcatus alluaudi, a subspecies of Potamonautes suprasulcatus (Hilgendorf, 1898) (Reed & Cumberlidge 2006); P. (G.) jeanneli as a junior synonym of Potamonautes (Platypotamonautes) neumanni (Hilgendorf, 1898); and P. (P.) odhneri as a junior synonym of Potamonautes (Platypotamonautes) pilosus (Hilgendorf, 1898). Williams (1968) did not entirely accept Bott’s (1955) opinions and recognized two species of freshwater crabs from Mt Kenya and the Aberdare Mountains (P. alluaudi and P. odhneri), and Williams (1991) recog- nized a third species, P. jeanneli, from high altitude localities east of the Rift Valley in the region that includes the Aberdare Mountains and Mt Kenya. The result of the above series of shifting taxonomic opinions has been that freshwater crabs collected from this area of Kenya have proved difficult to identify and because the only available keys are still those of Bott (1955). The present work has been prompted by the need to identify material from the central Kenyan highlands that was collected by T. R. Williams and his colleagues in the 1960s during a survey of highland areas with the potential to be a focus of onchocerciasis (river blindness), a parasitic disease of humans caused by Onchocerca volvulus, a tissue nematode. Freshwater crabs are obligate phoretic hosts of the aquatic larvae of biting blackflies (Simulium sp.) that are the main vectors of this disease in Africa (Barnley & Prentice 1958; Accepted by P. Castro: 24 Nov. 2008; published: 16 Jan. 2009 29 McMahon et al. 1958; Hynes et al. 1961; Williams et al. 1964; Williams 1964; Crosskey 1990). Other speci- mens included here were collected by M. Dobson during recent ecological studies of the freshwater aquatic communities of Mt Kenya (Dobson 2004; Dobson et al. 2002, 2007a, b). The species of Potamonautes from Mt Kenya redescribed here were collected from forests on the slopes of the mountain from streams, rivers, and nearby land. In the absence of reliable keys, the present revision is based on the examination of the type specimens of all of the relevant taxa, as well as a large series of specimens from this region collected since Bott’s (1955) monograph. The results indicate that Mt Kenya and the Aberdare Mountains support three valid species of Potamonautes MacLeay, 1838: P. jeanneli (Bouvier, 1921), P. odhneri (Colosi, 1924), and P. allu- audi (Bouvier, 1921), which are redescribed here based on characters of the carapace, thoracic sternum, cheli- peds, and G1. Specimens are deposited in the Natural History Museum, London, U.K. (NHM) and in the museum of the Department of Biology, Northern Michigan University, Marquette, MI, USA (NMU). The following abbreviations are used: CW, distance across the carapace at the widest point; CL carapace length measured along the median line, from the anterior to the posterior margin; CH, carapace height, the maximum height of the cephalothorax; FW, front width measured along the anterior margin; GO1, first gono- pod; s, thoracic sternite; s4/s5, s4/s5, s5/s6, s6/s7, s7/s8, sternal sulci between adjacent thoracic sternites; e, thoracic episternite; s4/e4, s5/e5, s6/e6, s7/e7, episternal sulci between adjacent thoracic sternites and epister- nites; p1–p5, pereiopods 1–5. MNHN = Muséum national d’Histoire Naturelle, Paris, France; SMF = Senck- enberg Museum, Frankfurt, Germany; SMNH = Swedish Museum of Natural History (Naturhistoriska Riksmuseet) Stockholm, Sweden; USNM = United States National Museum of Natural History, Smithsonian Institution, Washington DC, USA; ZMB = Museum für Naturkunde der Humboldt-Universität, Berlin, Ger- many. All measurements are given in mm. The terminology is adapted from Cumberlidge (1999). Taxonomy Family POTAMONAUTIDAE Bott, 1970 GenusPotamonautes MacLeay, 1838 Potamonautes jeanneli (Bouvier, 1921) (Figs. 1–16, 43, Table 1) Potamon (Geothelphusa) jeanneli Bouvier, 1921: 51–56, figs. 5, 6. Potamon jeanneli Chace, 1942: 214. Potamon jeanneli Capart, 1954: 834, fig. 22. Potamonautes jeanneli Williams, 1968: 214; Williams, 1991: 182. Type material examined. KENYA: adult male, Potamon (Geothelphusa) jeanneli (CW 22, CL 19.5, CH 7.1, FW 7.4 mm), mid-altitude forest (2,400–2,700 m) on western slopes of Mt Kenya, 22.i.1912 (CH. Alluaud and R. Jeannel coll.). This specimen was illustrated by Bouvier (1921, figs. 5, 6) and is one of four adult males that he referred to as types, and is herein designated the lectotype (Figs. 1–16). Other material. KENYA: Mt Kenya, Sirimon River (0°08'N, 37°06'E), 13–15 km north of Nanyuki on the road to Meru, 3.7 m wide, up to 0.6 m deep, part shaded, river bed with rounded stones, some larger blocks, 6 males (CWs 16.5 to CW 23.6 mm), one female (CW 14.5 mm) 8.iii.1962 (T. R. Williams) (NMU EA62.78). Diagnosis. Carapace smooth; anterolateral margin behind epibranchial tooth smooth, continuous with posterolateral margin; postfrontal crest missing, epigastric crests low, postorbital crests absent; exorbital tooth 30 · Zootaxa 1981 © 2009 Magnolia Press CUMBERLIDGE FIGURES 1–9. Potamonautes jeanneli (Bouvier, 1921) adult male (CW 21.2 mm) western slopes of Mt Kenya, Kenya. 1, cephalothorax, carapace and eyes, frontal view; 2, carapace and eyes, dorsal view; 3, carpus and merus of right che- liped, dorsal view; 4, merus of right cheliped, inferior view; 5; right cheliped, frontal view; 6, left cheliped, frontal view; 7, left fifth pereiopod; 8, anterior sternum; 9, abdomen. Scale = 6.6 mm. low, epibranchial tooth absent; carapace sidewalls smooth; vertical groove meeting anterolateral margin; ster- nal sulcus s2/s3 complete, horizontal, s3/s4 reduced to two notches; episternal sulci s4/e4, s5/e5, s6/e6, s7/e7 all missing; ischium of third maxilliped lacking vertical groove; first carpal tooth on carpus of cheliped low, second carpal tooth smaller; dactylus of major cheliped slightly arched, closed fingers enclosing long narrow FRESHWATER CRABS OF MT KENYA Zootaxa 1981 © 2009 Magnolia Press · 31 interspace; terminal article of G1 slim, almost straight, distal half curving slightly outward; lateral, medial folds of equal height; distal margin of subterminal segment highest on medial side forming pronounced shoul- der lowest on lateral side; dorsal membrane broad, widest at lateral edge, narrowest at medial edge. Size. Small-sized species, adult size range from CW 22 to CW 23.6 mm. Type locality. Kenya: mid-altitude forest on western slopes of Mt Kenya, from a fast-flowing mountain stream in a clearing in a bamboo forest (2,700 m asl). FIGURES 10–16. Potamonautes jeanneli (Bouvier, 1921) adult male (CW 22 mm) western slopes of Mt Kenya, Kenya. 10, left third maxilliped; 11, left mandible; 12, detail of terminal segment of the palp of the left mandible; 13, right G1, ventral aspect; 14, right G1, dorsal aspect; 15, terminal segment turned to show groove; 16, gonopod 2, ventral aspect. Scale = 6.6 mm (10); 2.7 mm (11–16). 32 · Zootaxa 1981 © 2009 Magnolia Press CUMBERLIDGE Distribution. Kenya: Mt Kenya (2,400–2,700 m asl), from streams in mid-altitude bamboo forest, from the Burguret River on an ascent trail of Mt Kenya in a podocarp forest (2,400 m asl), and from the Sirimon River. Natural history. This species lives in the rivers and streams draining the slopes of Mt Kenya and was first collected by members of the French Expedition led by Ch. Alluaud and R. Jeannel in 1912. Other material was collected fifty years later from Mt Kenya by T. R. Williams as part of an onchocerciasis study in 1962. Comments. The male lectotype of Potamon (Geothelphusa) jeanneli from Mt Kenya (CW 22 mm) was partly figured by Bouvier (1921, figs 5, 6). Although this species was originally described from an adult male the gonopods, anterior sternum, and chelipeds are described here for the first time. Colosi (1924) identified a male specimen (CW 28.3 mm) from Mt Elgon collected by S. A. Lovén, 30.vi.1920, from a steam at 4,000 m asl (SMNH 7556 ex. 13215) as P. (G.) jeanneli. However, it is by no means certain that this specimen actually belongs to this species, because the sketches provided in the original description and the locality indicate that it might be a misidentified subadult specimen of P. loveni (Colosi, 1924). Bott (1955) included Colosi’s (1924) P. (G.) jeanneli from Mt. Elgon in the synonymy of Potamonautes granviki, and treated Bouvier’s (1921) P. jeanneli from Mt Kenya, as a junior synonym of Potamonautes (Platypotamonautes) neumanni (Hilgendorf, 1898). However, the latter opinion is doubtful. The male lectotype of Telphusa neumanni (CW 35 mm) from Ngari Longai, Masailand, Kenya, 36°W, 1.5°S (ZMB 11386) was compared here with the adult male type of P. (G.) jeanneli from Mt Kenya (CW 22 mm). The G1 of P.jeanneli (Figs. 13–15) is clearly dif- ferent from that of the lectotype of P.neumanni (Bott 1955, fig. 14) and this raises doubts about the validity of Bott’s (1955) synonymization. Potamonautes jeanneli is resurrected here from synonymy with P. (P.) neu- manni and both taxa are treated as valid species. Conservation status. The conservation status of P. jeanneli from Mt Kenya is assessed as least concern (LC) because it has an extent of occurrence and area of occupancy that are both in excess of the thresholds for vulnerability (VU) and there are no known widespread threats (IUCN 2004; Cumberlidge et al. 2009). Its pop- ulation is estimated to be stable based on indirect measures such as its representation in museum collections, although it was most recently collected back in 1962 Potamonautes odhneri (Colosi, 1924) (Figs. 17–29, 44, Table 1) Potamon (Potamonautes) odhneri Colosi, 1924: 7–8, figs. 1, 3, pl. 4. Potamon odhneri Chace, 1942: 218. Type material examined. KENYA: Mt Kenya, 2,500 m asl, adult male (CW 23.5, CL 21 mm), figured by Colosi (1924), lectotype (here designated), 1911 (E. Lönnberg) (SMNH 7558 [ex. 11859, ex. 6430]); adult female (CW 23.5 mm), abdomen very broad but no eggs or hatchlings, paratype (here designated) (CW 25, CL 17.9, CH 9.3, FW 7.9 mm), forest near Meru, north of Mt Kenya, 19–30.i.1911 (E. Lönnberg) (SMNH 7557 [ex. 11852]) (Figs. 17–25); Limuru, southern Aberdare Mountains, 2 adult females, paratypes (here des- ignated) (largest CW 25.5, CL 16.9, CH 11.4, FW 7.8 mm). Other material. KENYA: northern Aberdare Mountains, Chania River below Kiandongoro Forestry sta- tion (2,187 m asl) (0°27'S, 36°50'E), river shallow, 6–9 m wide, river bed stony with boulders, partly tree shaded, adult male (CW 25.5, CL 16.9, CH 11.4, FW 7.8 mm) 17.iii.1962 (T. R. Williams coll.) (NMU EA62.114); Gituambugi/Mutonga Rivers, eastern slope of Mt Kenya, 2 males (CWs 23.6, 22.2 mm), iv.2003 (A. Magana coll.) (NMU 4.2003.1); Nano Moru River west of Mount Kenya, adult male (CW 32.5 mm) 14.7.2004 (M. Dobson coll.) (NMU MD 14.7.2004); Mt Kenya, Smithsonian Africa Expedition (Theodore Roosevelt coll.) x.1909 (USNM 57304); Mt Kenya, adult male, CW 24.1 mm (USNM 82312) (Figs. 26–29, 44). FRESHWATER CRABS OF MT KENYA Zootaxa 1981 © 2009 Magnolia Press · 33 FIGURES 17–25. Potamonautes odhneri (Colosi, 1924) adult femaleparatype (CW 25 mm) (SMNH 7557), Mt Kenya, Kenya. 17, carapace and eyes, dorsal view; 18, cephalothorax, carapace and eyes, frontal view; 19, carpus and merus of right cheliped, dorsal view; 20, merus of right cheliped, inferior view; 21; right cheliped, frontal view; 22, left cheliped, frontal view; 23, left third maxilliped; 24, left mandible; 25, detail of terminal segment of the palp of the left mandible. Scale = 6.1 mm (17–20, 21–23); 3.3 mm (24–25). 34 · Zootaxa 1981 © 2009 Magnolia Press CUMBERLIDGE FIGURES 26–29. Potamonautes odhneri (Colosi, 1924) adult male (CW 24.1 mm) (USNM 82312), Mt Kenya, Kenya. 26, anterior sternum; 27, right G1, ventral aspect; 28, right G1, dorsal aspect; 29, gonopod 2, ventral aspect. Scale = 3.3 mm. Diagnosis. Carapace smooth; anterolateral margin behind epibranchial tooth faintly granulated, curving inward over carapace in branchial region; postfrontal crest sharp; exorbital tooth low, epibranchial tooth reduced to a granule; carapace sidewalls smooth; vertical groove meeting anterolateral margin; sternal sulcus s2/s3 complete, horizontal, s3/s4 reduced to two side notches; episternal sulci s4/e4, s5/e5, s6/e6, s7/e7 all vis- ible; third maxilliped ischium with vertical groove; first carpal tooth of cheliped carpus chsmall, pointed, sec- ond carpal tooth small, granular, followed by several other granules; dactylus of major cheliped highly arched, closed fingers enclosing wide oval interspace; terminal article of G1 curving sharply outward at 45° angle to longitudinal axis of gonopod; lateral, medial folds unequal, high; distal margin of subterminal segment high- est on medial side forming pronounced shoulder lowest on lateral side; dorsal membrane broad, widest at lat- eral edge, narrowest at medial edge. Size. Small-sized species, pubertal molt occurring around CW 23.5 mm, adult size range up to CW 32.5 mm. Type locality. Mt Kenya and the Aberdare Mountains, Kenya. Distribution. Mt Kenya and the Aberdare Mountains, in the highlands of central Kenya. FRESHWATER CRABS OF MT KENYA Zootaxa 1981 © 2009 Magnolia Press · 35 Remarks. This species was originally described from an adult female, so this is the first time that the gonopods, sternum, and chelipeds of P. odhneri have been described. The specimens from Mt Kenya and the Aberdare Mountains included here were identified following comparison with the male lectotype and the female paratype of Potamon (Potamonautes) odhneri from the forest near Meru, north of Mt Kenya (SMNH 7557), which was examined in the present study and figured by Colosi (1924). Bott (1955) treated P. odhneri as a junior synonym of Potamonautes (Platypotamonautes) pilosus (Hilgendorf, 1898). However, Reed & Cumberlidge (2006) doubted this synonymization following examination of the female paratype of P. (P.) odhneri from Meru, Kenya and the male lectotype of Telphusa pilosa Hilgendorf,1898 (ZMB 11387) from a rain forest near Maranga at the base of Mt Kilimanjaro, Tanzania. Those authors pointed out that Bott’s (1955) photographs of P. pilosus (Pl. V, 1a–d) actually show the female paratype of P. (P.) odhneri Colosi, 1924 (SMNH 7558, CW 23, CL 17, CH 10, FW 7.5 mm) from Limuru, near Mt Kenya, Kenya, and not the lecto- type of T. pilosus. In addition, Williams (1968) also doubted Bott’s (1955) opinion regarding these two taxa. Potamonautes odhneri is therefore resurrected from synonomy and recognized here as a valid species. Conservation status. The conservation status of P. odhneri is categorized as least concern (LC) because it has an extent of occurrence and an area of occupancy that are both in excess of the thresholds for vulnerable (VU) and there are no known widespread threats (IUCN 2004; Cumberlidge et al. 2009). Its population is esti- mated to be stable based on indirect measures such the fact that it is well represented in museum collections, and because it has been collected recently. Potamonautes alluaudi (Bouvier, 1921) (Figs. 30–42, 45, Table 1) Potamon (Geothelphusa) alluaudi Bouvier, 1921: 46–49, figs. 1–3. Potamon alluaudi Balss, 1929: 350; Chace, 1942: 240. Type material examined: KENYA: holotype, Potamon (Geothelphusa) alluaudi Bouvier, 1921, female sub- adult (CW 26.5, CL 18.9, CH 9.7, FW 7.8 mm), Ruaha River. Nairobi Forest (0°24'0''S, 36°59'0''E), 1,000 m asl, 25 km from Nairobi, Central Province, 22.ii.1911 (Ch. Alluaud and R. Jeannel coll.) (MNHN B-17); spec- imen illustrated is the adult male (CW 54 mm) from the Aberdare Mountains (T.R. Williams coll.) (NMU TRW 1963.02a.1-2). Additional material examined: KENYA: Amboni River, southern Aberdare Mountains, subadult female (CW 21 mm) (damaged); Kiganjo, northern Mt Kenya, Chania River at road bridge below Nyeri (0°06'S, 37°52'E) river 6.1 m wide, fast, river bed with small boulders and stones, 7 juveniles (CW 12.7 to CW 21 mm), juvenile female (CW 22.2 mm), male (CW 32.2 mm), subadult female (CW 34.9 mm), male (damaged), 7.iii.1962 (T. R. Williams coll.) (NMU TRW EA62.75); Mt Kenya, Kiganjo, Nairobi River on road to Trout Research Station, river bed sandy with large stones, and occasional small waterfalls flowing over outcrops and large rocks, 7.iii.1962 (T. R. Williams coll.) (NMU TRW EA62.76); Meru, northern Mt Kenya, Kiganjo, first stream north of last station, 2–2.5 m wide, open, stream bed sandy with some embedded large stones and a cattle watering pool, 9.iii.1962 (T. R. Williams coll.) (NMU TRW EA62.85); Nyambeni Hills, north of Mt Kenya, Thangatha River (0°07'S, 38°13'E), 1,585 m asl, 8.4 km from Mikinduri (00°07'N, 37°50'E) river 3.7–4.6 m wide, river bed stony with some boulders, shaded, at forest edge, about 90 juveniles, 10.iii.1962 (T. R. Williams coll.) (NMU TRW EA62.89); Nyambeni Hills, north of Mt Kenya, Thangatha River, 1,585 m asl, from mid stream, adults, 10.iii.1962 (T. R. Williams coll.) (NMU TRW EA62.91); Nyambeni Hills north of Mt Kenya, unnamed stream, 1.2 km nearer Mikindwi than Thangatha River, 0.7 m wide, shallow, river bed with occasional boulders, otherwise sandy with a few stones, crab collected from beneath a boulder, adult male, 10.iii.1962 (T. R. Williams coll.) (NMU TRW EA62.93); Nyembeni Hills, north of Mt Kenya, Ngobit River at Ngobit on road between Naro Moru and Rumuruti (1°17'N, 36°47'E), a tributary of the Ewaso Ngiri River, river 3.7–4.6 m wide, up to 0.7 m deep, river bed with gravel embedded in silty clay, occasional large 36 · Zootaxa 1981 © 2009 Magnolia Press CUMBERLIDGE stones, crab collected from rubble at sides of river below bridge, juvenile male (CW 27.9 mm), 16.iii.1962 (T. R. Williams coll.) (NMU TRW EA62.106); Mt Kenya, juvenile female (CW 19.9 mm), 1972 (Joy coll.) (NMU JOY 07.2001.a.1) Mt Kenya, juvenile male (CW 32.4 mm), juvenile female (damaged) i.1972 (Joy coll.) (NMU TRW 01.1972.2); Chania River, Nyeri, Aberdare Mountains (M. J. Clarkson coll.) adult male (CW 46.8 mm) adult female (CW 51.5 mm) (NMU TRW 1963.02b.1–2); Meru, Mt Kenya, 10.iii.1962 (NHM 10.III.1962.1); Murang’a (formerly Fort Hall), male (USNM 82309); Mt Kenya, 2 females (CWs 54.5, 50.0 mm), male (CW 48.9 mm), 29.ix.1909 (Smithsonian African Expedition coll.) (USNM 82317); Mt Kenya, Murang'a (formerly Ft. Hall), 2,833 m asl, juvenile (damaged), 4 males (CW 23.1 to CW 48.9 mm), 2 juvenile males (CW 17.2 to CW 21.8 mm), 6 females (CW 23.7 to CW 36 mm), 2 juveniles (CW14.6 to CW 15.6 mm), ovigerous female (CW 51.8 mm), x.1909 (Smithsonian African Expedition coll.) (USNM 82318); Kasa- rongai River, west of Mt Kenya, 15 males (CW 27.1 to CW 48.7 mm), 9 females (CW 24.9 to CW 35.1 mm), 3 juveniles (CW 7.4 to CW 21.9 mm) x.1909 (Smithsonian African Expedition coll.) (USNM 82319); Kasa- rongai River, west of Mt Kenya, adult male, 3 subadult males, 3 juvenile males, 3 adult females (CW 46.6 to CW 53 mm), 2 adult females with hatchlings, ovigerous female, 6 subadult females, 9 juvenile females, 7 juveniles, x.18–19.1909 (Smithsonian African Expedition coll.) (USNM 82320); Mt Kenya to Murang'a (for- merly Fort Hall), 2,833 m asl, 15 males (CW 18.8 to CW 41 mm), 7 females (CW 21.5 to CW 51.8 mm), 3 juvenile females (CW 18 to CW 25.3 mm), 11 juvenile males (CW 17.5 to CW 23.7 mm), 25 juveniles (CW 12.6 to CW 24.4 mm), juvenile (damaged), female subadult (damaged), x.1909 (Smithsonian African Expedi- tion coll.) (USNM 82321); Kasarongai River, west of Mt Kenya, 27 males, 32 females (17 juve- niles),18–19.x.1909 (E. A. Mearns) (USNM 82322); between Mt Kenya and Murang'a (formerly Fort Hall), 2,833 m asl, 27 juveniles (CW 10.3 to CW 25.9 mm), 14 juvenile females (CW 19.4 to CW 31.8 mm), 5 juve- nile males (CW 20.9 to CW 32.7 mm), subadult female (CW 38.5 mm), female subadult (CW 39.5 mm), adult female (CW 47 mm), female with hatchlings (CW 44.3 mm), 2 juveniles (damaged), x.1909 (Smithsonian African Expedition coll.) (USNM 82323). Diagnosis. Carapace medium height (CH/FW 1.3), smooth; anterolateral margin granular; postfrontal crest distinct, completely crossing carapace, granular at junction with anterolateral margins; exorbital, epi- branchial teeth low; carapace sidewalls smooth; third maxilliped ischium with deep vertical sulcus; thoracic sternal sulcus s3/s4 not complete, v-shaped, tapering inward at sides, absent across middle; episternal sulcus s4/e4 absent, s5/e5, s6/e6, s7/e7 complete; dactylus of major cheliped broad, highly arched, closed fingers enclosing oval interspace; first carpal tooth on carpus of cheliped large, blunt; second carpal tooth reduced to small granule, followed by several other small granules; ventral margins of pereiopod 1 merus granulated; dis- tal meral tooth pointed; terminal article of G1 curving outward at 60° angle to longitudinal axis of gonopod; terminal article broad proximally (lateral, medial folds high in basal half), terminal article outwardly curved, narrowing distally, tapering to point; distal margin of subterminal segment highest on medial side (forming rounded shoulder) lowest on lateral side; dorsal membrane broad, widest at lateral edge, narrowest at medial edge. Size. A large-sized species, pubertal molt between CW 44 and CW 54.5 mm. Type locality. Ruaha River, Nairobi Forest, Kenya. Distribution. Kenya, in the region of Mt Kenya and the Aberdare Mountains, Central Province. The records from the NMU collection combined with those the USNM collected by the Smithsonian African Expedition in 1909 that have been re-identified here define the species as endemic to the highlands of the Central Province of Kenya, in the region of Mt Kenya and the Aberdare Mountains. Bouvier (1921) also included in this species an adult male syntype from the Amboni River (1,800 m asl) in the Aberdare Moun- tains collected on January 13, 1912. However, Bouvier’s (1921) further inclusion in this species of two male specimens from the Ngare Rongai (now Ngare Longai) River in the grasslands east of Mt. Kilimanjaro is con- sidered doubtful, and these are not listed under this species in the present work. FRESHWATER CRABS OF MT KENYA Zootaxa 1981 © 2009 Magnolia Press · 37 FIGURES 30–42. Potamonautes alluaudi (Bouvier, 1921) adult male, CW 54 mm, NMU TRW 1963.02a.1–2, Chania River, Nyeri, Aberdare Mountains, Kenya. 30, carapace and eyes, dorsal view; 31, cephalothorax, carapace and eyes, frontal view; 32, carpus of right cheliped, dorsal view; 33, merus of right cheliped, dorsal view; 34, merus of the right cheliped, inferior view; 35; right cheliped, frontal view; 36, left cheliped, frontal view; 37, left third pereiopod; 38, left fifth pereiopod; 39,left third maxilliped ; 40, sternum; 41, right G1, ventral aspect; 42, right G1, dorsal aspect. Scale = 16.4 mm (30–40); 3.6 mm (41–42). 38 · Zootaxa 1981 © 2009 Magnolia Press CUMBERLIDGE