A NEW FRESHWATER CRAB FROM PRINCIPE 
ch 14.8, fw 10.5 mm, summit of Pico do Principe (01° 34’, 51"N, 07° 
22', 57"E), 945 m, coll. J. E. M. Baillie, 26 Sept. 1999. 
Paratype. BMNH 2001.6908.1 subadult female, cw 33.2, cl 22.8, 
ch 11.6, fw 10.0 mm, summit of Pico do Principe (01° 34’, 51"N, 07° 
22', 57"E), 945 m, coll. J. E. M. Baillie, 1 Sept. 1999. 
DIAGNOSIS. Postfrontal crest straight, smooth, spanning entire 
carapace, ends meeting anterolateral margins at epibranchial teeth. 
Exorbital tooth small, pointed; epibranchial tooth represented only 
by small granule; anterolateral margin posterior to epibranchial 
tooth raised, completely smooth, continuous with posterolateral 
margin. Carapace surface completely smooth; highly arched, height 
greater than front width (ch/fw 1.5). Pleural (vertical) suture on 
carapace sidewall Y-shaped, ends meeting exorbital and epibranchial 
teeth. Suborbital margin raised, completely smooth. Ischium of third 
maxilliped with deep vertical sulcus. Third sternal sulcus s3/s4 
deep, v-shaped, meeting sterno-abdominal cavity. Thoracic epister- 
nal sulci s4/e4, s5/e5, s6/e6 and s7/e7 distinct. Anterior inferior 
margin of merus of cheliped lined by row of small sharp teeth, with 
large pointed tooth near junction with carpus. 
DESCRIPTION. Carapace ovoid, wide (cw/fw 3.88), highly arched 
(ch/fw 1.45); surface completely smooth semi-circular, urogastric, 
transverse branchial grooves faint. Front straight, relatively narrow, 
about one-quarter carapace width (fw/cw 0.26), anterior margin 
sharply deflexed. Postfrontal crest distinct, smooth, straight, span- 
ning entire carapace, consisting of fused epigastric, postorbital 
crests; ends of postfrontal crest meeting anterolateral margins at 
epibranchial teeth. Anterolateral margin between exorbital, 
epibranchial teeth smooth, lacking intermediate tooth; anterolateral 
margin posterior to epibranchial tooth raised, completely smooth, 
continuous with posterolateral margin. Exorbital tooth small, pointed; 
epibranchial tooth represented only by small granule. Suborbital 
margin raised, completely smooth. Suborbital, subhepatic, 
pterygostomial regions all completely smooth; sidewall divided into 
three parts by longitudinal (epimeral) suture (dividing suborbital, 
subhepatic regions from pterygostomial region), and by Y-shaped 
vertical (pleural) groove (dividing suborbital from subhepatic 
regions). Superior ends of Y-shaped vertical groove meeting 
exorbital, epibranchial teeth. First thoracic sternal sulcus s1/s2 deep; 
second sulcus s2/s3 deep, running horizontally across sternum; third 
sulcus s3/s4 deep, v-shaped, meeting sterno-abdominal cavity. Tho- 
racic episternal sulci s4/e4, s5/e5, s6/e6 and s7/e7 distinct. Third 
maxillipeds filling entire oral field, except for transversely ovate 
respiratory openings at superior lateral corners; long flagellum on 
exopod of third maxilliped; ischium with deep vertical sulcus. 
Epistome prominent, smooth, triangular. Mandibular palp 2-seg- 
mented; terminal segment single, undivided, with hair (but no hard 
flap) at junction between segments. Subadult female abdomen 
subcircular, segments al—a6 of female abdomen quadrate, telson 
(a7) a broad triangle with rounded apex; segments a5—a6 broadest. 
Major cheliped of subadult female relatively slender, with elon- 
gated dactylus and propodus, palm of propodus swollen; fingers of 
digits of cheliped with small even teeth, forming long narrow 
interspace when closed. First carpal tooth of inner margin of carpus 
of cheliped large, pointed; second carpal tooth pointed, half size of 
first tooth. Posterior inferior margin of merus of cheliped smooth, 
with few small teeth distally; medial inferior margin with row of 
small sharp teeth along entire length, large pointed tooth at distal 
end; superior surface of merus smooth. Pereiopods P2—P5 slender, 
P3 longest, PS shortest. Dactyli of P2—P5 tapering to point, each 
bearing four rows of downward-pointing short, sharp spines. 
CoLour. Thecolour of the specimens when freshly caught (before 
15 
alcohol preservation) was creamy white with a very light purplish 
tone, however one specimen was more white than the other. This 
coloration was relatively uniform throughout the body including the 
dorsal carapace, underside, and legs. The purplish tone was darker 
on the carapace just behind the eyes, which turned to an orange 
reddish color once the specimens were placed in alcohol. 
DISTRIBUTION. This species is known only from the summit of the 
Pico do Principe: (01° 34", 51'N, 07° 22', 57"E) at 945 meters, The 
Democratic Republic of Sao Tomé and Principe, Gulf of Guinea, 
Central Africa. 
ETYMOLOGY. The species is named for the island of Principe 
where it was collected. The species name principe is a noun in 
apposition. 
TAXONOMIC REMARKS. The new species is assigned to Pota- 
monautes because it possesses the following combination of 
characters: the anterolateral margin lacks an intermediate tooth 
between the exorbital and epibranchial teeth; the mandibular palp is 
two-segmented; and the third maxilliped exopod has a long flagellum. 
Potamonautes is a widespread genus of African freshwater crabs 
found throughout Africa from Senegal to the Horn of Africa, and 
from Egypt to South Africa. Bott’s (1955) revision of the freshwater 
crabs of Africa recognised some 34 species in this genus. Since then, 
the number of species of Potamonautes has risen to more than 60 
(Bott, 1959, 1960, 1964, 1968, 1970; Stewart et al., 1995; Stewart, 
1997a,b; Daniels et al., 1998; Cumberlidge, 1999; Corace et al., 
2001). Although Bott (1955) recognised 15 subgenera of 
Potamonautes, the authors of the present study prefer to follow 
Cumberlidge (1999) and use Potamonautes [sensu lato | for all 
species, pending a revision of the entire genus (Cumberlidge, un- 
published). 
It is not normally good practice to describe a new species from a 
subadult female. However, we have decided to establish this taxon 
in the light of the distinct nature of the available morphological 
characters, and because of the isolated nature of the study area which 
may mean that further specimens of P. principe are unlikely to 
become available for some time. Characters of the gonopods, adult 
male chelipeds, abdomen and sternum are not at present known 
because the only specimens of P. principe are subadult females. 
Nevertheless, there are a number of unique characters that distinguish 
P. principe from other species in the genus. 
COMPARISONS WITH OTHER SPECIES. Potamonautes principe is 
closest to P. anchietae, a medium-sized species of freshwater crab 
from Angola (De Brito-Capello, 1871, Bott, 1953, 1955, 1964). This 
species was most recently described and illustrated by Bott (1955, p. 
247-249, figs. 24, 76, 77, pl. IX, fig. la—d) as P. (Isopotamonautes) 
anchietae. Potamonautes principe and P. anchietae are similar in 
that both species have a highly arched carapace, a prominent and 
complete postfrontal crest, a pointed exorbital tooth, a small granu- 
lar epibranchial tooth, a v-shaped thoracic sternal groove s3/s4, and 
a similar-sized first carpal tooth on the carpus of the cheliped. 
However, there are a number of characters that distinguish the 
specimens from Vissabenguilla, Angola (SMF 1890) described by 
Bott (1955) as P. (/.) anchietae from the specimens from Principe 
under consideration here. 
The carapace height of P. principe is greater than that of P. 
anchietae (ch/fw P. principe 1.45, P. anchietae 1.19), and the frontal 
margin of P. principe is narrower than that of P. anchietae (fw/cw P. 
principe 0.26, P. anchietae 0.39). Further, the anterolateral margins 
of the carapace of P. principe are completely smooth and lack teeth 
of any kind, whereas these margins in P. anchietae are distinctly 
granular. The medial inferior margin of the merus of the cheliped of 
