taxonID	type	description	language	source
03C787B8FFA4FFF9B6CF5710FBCDD2B7.taxon	diagnosis	Diagnosis Based on female type from Liranga. Exorbital tooth large, spine-like; lateral margin of exorbital tooth lined by small teeth, angled outward at 45 ° to midline of carapace, straight, neither bulging outward (convex) nor curving inward (concave); epibranchial tooth small, pointed, as large as other denticles lining anterolateral margin (Fig. 4 A). Anterolateral margin posterior to epibranchial tooth curving strongly outward (Fig. 4 A); postfrontal crest distinct, completely traversing carapace between epibranchial teeth; posterior surface of carapace with deep urogastric grooves; cheliped carpus inner margin with two large, subequal, forwardpointing spines (Fig. 7 A); cheliped merus inner lower margin with spine-like tooth distally.	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFA4FFF9B6CF5710FBCDD2B7.taxon	materials_examined	Material examined Holotype (by original designation) REPUBLIC OF THE CONGO • 1 ♀ adult (dried, CW 43.7, CL 38, FW 14.5 mm); Liranga, Middle Congo River, at the confluence of the Congo and Oubangi Rivers; 5 Sep. 1891; J. Dybowski leg.; MNHN B- 3826.	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFA4FFF9B6CF5710FBCDD2B7.taxon	description	Description See Diagnosis. Size Medium-sized species, adult at CW 43 mm. Colour The preserved specimen from Liranga is uniformly light brown.	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFA4FFF9B6CF5710FBCDD2B7.taxon	distribution	Distribution The revised distributional range of P. lirrangensis s. str. (Fig. 1) now comprises just the Middle Congo River: Liranga (not ‘ Lirranga’ as implied from the specific epithet) in the République du Congo. This species now excludes specimens formerly identified as P. lirrangensis s. lat. from Kisangani in the D. R. Congo (Fig. 1), rivers near Kigoma draining into Lake Tanganyika, in Tanzania, Lake Tanganyika in Zambia (Fig. 3), and Lake Malawi in Malawi (Fig. 2).	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFA4FFF9B6CF5710FBCDD2B7.taxon	biology_ecology	Ecology The type locality of P. lirrangensis s. str. in the Middle Congo River (Liranga) lies in the Sudanic Congo-Oubangi Ecoregion (Freshwater Ecoregions Of the World (FEOW # 535) (Thieme et al. 2005; Abell et al. 2008). This is more than 1000 km from Kisangani where Potamonautes kisangani sp. nov. is found in the Upper Congo Rapids Ecoregion (FEOW # 539), which indicates that the habitats of these 2 taxa are different, despite both being located in the Middle Congo River. Interestingly, these 2 taxa are separated by a third ecoregion, the Cuvette Centrale (FEOW # 537).	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFA4FFF9B6CF5710FBCDD2B7.taxon	discussion	Comparisons Taxonomically important characters of the male cheliped, thoracic sternum, and gonopods, and the colour when alive, together with DNA data for P. lirrangensis s. str. will not be available until topotypal material is collected that includes an adult male. The carapace of the female type specimen from Liranga was illustrated by Capart (1954: fig. 28) and photographed by Rathbun (1904: pl. 14 fig. 8) and (together with the cheliped carpus) have been included in the present study (Figs 4 A, 7 A). The lateral margin of the exorbital tooth of P. lirrangensis s. str. from Liranga (Fig. 4 A) is similar to that of P. kisangani sp. nov. from Kisangani (Fig. 4 B; Rathbun 1904: fig. 8 a) and is angled outward at 45 ° to the midline of the carapace and is straight and neither bulges outward (convex) nor curves inward (concave). This contrasts with that of P. amosae sp. nov. from Lake Kivu (Fig. 4 C) and the Malagarasi River (Reed & Cumberlidge 2006: pl. 5 a), where the lateral margin of the exorbital tooth is not straight and bulges distinctly outward (convex) before meeting the postfrontal crest. This also contrasts with P. orbitospinus from Lake Malawi (Fig. 4 E) where the lateral margin of the exorbital tooth curves inward (concave) and is neither straight nor convex. The identifications of specimens as P. lirrangensis s. lat. by a number of authors (Rathbun 1921; Chace 1942; Bott, 1955; Reed & Cumberlidge 2006; Cumberlidge & Meyer 2011) are all now considered unreliable because they conflate characters from the 4 taxa that comprise the species complex under study here. Specifically, the descriptions of the male characters of P. lirrangensis s. lat. by the above authors combined characters from specimens from Kisangani, Lake Kivu, Tanzania, and Lake Malawi (Table 1). Three taxonomic consequences of the treatment of P. lirrangensis s. lat. by Bott (1955) are addressed here. For example, that Bott (1) established the subgenus Potamonautes (Lirrangopotamonautes) Bott, 1955 with Potamon (Potamonautes) lirrangensis from Liranga, Middle Congo River as the type species; (2) included 3 taxa in this subgenus: Potamonautes (Lirrangopotamonautes) lirrangensis, P. (L.) j. johnstoni (Miers, 1885) and P. (L.) johnstoni platycentron Hilgendorf, 1897; and (3) treated Potamon (Potamonautes) orbitospinus as a junior synonym of P. (L.) lirrangensis. The subgenus Potamonautes (Lirrangopotamonautes) Bott, 1955, however, has not been recognized by subsequent authors due to doubts about the monophyly of a group comprising these 3 taxa (Reed & Cumberlidge 2006; Ng et al. 2008). Currently, P. johnstoni (Reed & Cumberlidge 2006: 21 – 23, figs 31 – 40, 151 – 152, 176 pl. IV) and P. platycentron (Reed & Cumberlidge 2006: 30 – 31, figs 82 – 92, 161 – 162, 181 pl. IX) are each recognized as valid species, while the taxonomic status of P. orbitospinus is addressed in the present study.	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFA4FFF9B6CF5710FBCDD2B7.taxon	conservation	Conservation status The current IUCN extinction risk assessment of LC for P. lirrangensis s. lat. was based on the extremely wide range of that taxon (Cumberlidge 2018). The present work reduces the range of P. lirrangensis s. str. significantly (Fig. 1), from an estimated extent of occurrence (EOO) of almost 1.5 million km 2 based on 58 localities, to a single locality that precludes the calculation of the EOO. This change will no doubt impact the conservation assessment of this species when it is revised.	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFA7FFE3B55B56E6FD4BD7BE.taxon	description	urn: lsid: zoobank. org: act: 77 F 6 D 732 - 392 A- 4 B 60 - AA 4 A-AA 2104 D 12 C 01 Figs 1, 4 B, 5 A, 6 A – B, 7 B, 8, 11 A, Table 1	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFA7FFE3B55B56E6FD4BD7BE.taxon	diagnosis	Diagnosis Exorbital tooth large, spine-like; lateral margin of exorbital tooth lined by small teeth, angled outward at 45 ° to midline of carapace, straight, neither bulging outward (convex) nor curving inward (concave); epibranchial tooth small, granular, followed by large granules lining anterolateral margin (Fig. 4 B); anterolateral margin posterior to epibranchial tooth curving strongly outward (Fig. 4 B); postfrontal crest distinct, completely traversing carapace between epibranchial teeth; posterior surface of carapace with deep urogastric grooves (Fig. 4 B). Male thoracic sternal sulcus S 3 / 4 deep, distinct, V-shaped. Ischium of third maxilliped with thin but distinct vertical sulcus. Major chela with 3 large molars at proximal end of both fingers (Fig. 6 A – B); major chela dactylus (moveable finger) and fixed finger (pollex of propodus) both elongated, straight, slender (Fig. 6 A – B); cheliped carpus inner margin with 2 large, subequal, forward-pointing spines (Fig. 7 B); cheliped merus inner lower margin with spine-like tooth distally. P 5 carpus, propodus, and dactylus all shortened (Fig. 8 A – B). G 1 TA conspicuously widened by high, rounded dorsal lobe (as wide as TA width at TA-SA junction); G 1 TA distal third straight, ending in pointed tip (Fig. 11 A). G 1 SA at junction with G 1 TA with horizontal margin on ventral side, U-shaped indentation filled by conspicuous dorsal membrane on dorsal side.	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFA7FFE3B55B56E6FD4BD7BE.taxon	etymology	Etymology The new species is named for Kisangani, D. R. Congo, the locality where it was first collected. The specific epithet is used as a Latin noun in apposition. The vernacular name is the Kisangani freshwater crab.	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFA7FFE3B55B56E6FD4BD7BE.taxon	materials_examined	Material examined Holotype DEMOCRATIC REPUBLIC OF THE CONGO • ♂ adult (CW 60.5 mm); Kisangani, vicinity of Wagenia fishery; 25 Apr. 1955; Smithsonian-Bredin Congo Exped., W. L. Schmitt leg.; USNM 98944. Paratypes DEMOCRATIC REPUBLIC OF THE CONGO • 2 ♂♂ (CW 59.5, 39.4 mm), 10 ♀♀ (CW 62.7, 61.1, 59.2, 56.9, 56.8, 56, 51.6, 48.3, 44.5, 40.3 mm), 3 ♀♀ ovig. (CW 66.5, 62.8, 54.7 mm); same collection data as for holotype; USNM 98944. Other material DEMOCRATIC REPUBLIC OF THE CONGO • 1 ♂, 1 ♀, 1 ♀ ovig.; Kisangani; Feb. 1915; A. M. Congo Exped., H. Lang leg.; USNM 54305 • 3 ♀♀ (CW 59.8, 54.9, 45.1 mm), 1 ♀ ovig. (CW 54.8 mm); same collection data as for preceding; Apr. 1915; USNM 54306 • 5 ♀♀ (CW 51.9, 49, 48.9, 45.6, 36.8 mm), 2 ♂♂ (CW 60.2, 29.2 mm); same collection data as for preceding; USNM 54307 • 1 ♂ (CW 59.1 mm); Kisangani, vicinity of Wagenia fishery; W. L. Schmitt Bredin Exped. leg.; USNM 98939 • 3 ♀♀ (CW 40.4, 40, 24.8 mm); rocky gorge of Tshope Falls, Kisangani; 19 Apr. 1955; Smithsonian-Bredin Congo Exped., W. L. Schmitt leg.; USNM 98940 • 1 ♀ (CW 53.6 mm), 3 juvs; Kisangani, vicinity of Wagenia fishery; Smithsonian-Bredin Congo Exped., W. L. Schmitt leg.; USNM 98941 • 2 ♀♀ ovig. (CW 56.5, 53.7 mm), 1 ♀ (CW 62.6 mm); Kisangani; 20 Apr. 1955; Smithsonian-Bredin Congo Exped., W. L. Schmitt leg.; USNM 98942 • 1 ♀ (with hatchlings, CW 60.1 mm); Kisangani; 20 Apr. 1955; Smithsonian-Bredin Congo Exped., W. L. Schmitt leg.; USNM 98943 • 1 ♂ (subadult CW 47.2 mm); Kisangani; 22 Jun. 1955; G. Browne leg.; NHMUK 1955.6.22.65 • 1 ♂, 1 ♀; Kisangani; Apr. 1915; A. M. Congo Exped., H. Lang leg.; MCZ CRU- 10613.	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFA7FFE3B55B56E6FD4BD7BE.taxon	description	Description See Diagnosis. Size Large-sized species, adult at CW 53 mm, largest known specimen CW 66 mm. Colour The colour of living specimens from Kisangani D. R. Congo was provided by Rathbun (1921: 415). The dorsal carapace is either dark blue, dark green, or dark brown, the thoracic sternum is pink with blue / gray tones, and the pleon is yellow / white. The fixed and movable fingers of the chelae are dark brown / black in recently preserved specimens (Fig. 6 A – B), while the arthrodial membranes of the chelipeds are vermillion (vivid red / orange).	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFA7FFE3B55B56E6FD4BD7BE.taxon	distribution	Distribution This species is only known from the vicinity of Kisangani in the D. R. Congo (Fig. 1).	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFA7FFE3B55B56E6FD4BD7BE.taxon	biology_ecology	Ecology Kisangani lies in the Upper Congo Rapids Ecoregion (FEOW # 539) (Thieme et al. 2005; Abell et al. 2008). The field notes of Herbert Lang on the habitat of P. kisangani sp. nov. from Kisangani provided by Rathbun (1921: 415) indicate that although this species is found in large rivers, it favours shallow waters near river banks where drifting logs jam. At the Boyoma Falls near Kisangani these crabs were common above and below the cataracts, while in the Tshopo River crabs were abundant among the rocks and boulder fields above the Tshopo Falls, but were absent below the falls where the water was shallow and had a sandy substrate.	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFA7FFE3B55B56E6FD4BD7BE.taxon	discussion	Remarks This new species was recognized to accommodate a large number of specimens from Kisangani, D. R. Congo that were collected by two U. S. Expeditions: the American Museum Congo Expedition (1909 – 1915) led by Herbert O. Lang and James P. Chapin, and the Smithsonian-Bredin Expedition to the Belgian Congo, Sudan, Uganda, and Egypt (1955) led by Waldo L. Schmitt. The first U. S. expedition initially deposited a large number of specimens (in 10 samples) in the AMNH and subsequently gifted some of these (USNM 54305, 54306, 54307 and MCZ CRU- 10613) to these other museums. All of the specimens from the first U. S. Congo expedition were attributed by Rathbun (1921) to P. lirrangensis s. lat., and she provided a description, photographs, and illustrations of this species (Rathbun 1921: 413 – 415, pls 25 – 26, figs 3, 8). The second U. S. Congo expedition in 1955 also collected a number of specimens (in 7 samples) from Kisangani (examined in the present work) that were also initially attributed to P. lirrangensis s. lat. Figures of the carapace, chelipeds, and G 1 of the adult male holotype from Kisangani, D. R. Congo (Figs 4 B, 5 A, 6 A – B, 7 B, 8 A – B, 11 A) are provided for comparison with the other taxa included here. One character that distinguishes this species from P. lirrangensis s. str. is the epibranchial tooth, which is small and granular, followed by large granules lining the anterolateral margin in P. kisangani sp. nov. (Fig. 4 B) (vs pointed and as large as the other teeth lining the anterolateral margin in P. lirrangensis s. str. from Liranga; Fig. 4 A). The absence of DNA sequence data for any of the specimens from Kisangani means that it is not possible to test the monophyly of P. kisangani sp. nov. using molecular data. Comparisons The epibranchial tooth and anterolateral margin of P. kisangani sp. nov. from Kisangani (Fig. 4 B) and of P. amosae sp. nov. from Lake Kivu (Fig. 4 C) and the Malagarasi River (Fig. 4 D; Reed & Cumberlidge 2006: pl. 5 a) are similar in both species: the epibranchial tooth is a small granule that is followed by large granules lining the anterolateral margin. In contrast, the epibranchial tooth of P. lirrangensis s. str. from Liranga (Fig. 4 A) and of P. orbitospinus from Lake Malawi (Fig. 4 E) is pointed and as large as the other teeth lining the anterolateral margin. The male thoracic sternal sulcus S 3 / 4 of P. kisangani sp. nov. from Kisangani (Fig. 8 B) and of P. orbitospinus from Lake Malawi (Fig. 10 B) is deep, distinct, and V-shaped, whereas this sulcus is faint in P. amosae sp. nov. from Lake Kivu (Fig. 9 B) and the Malagarasi River (Reed & Cumberlidge 2006: pl. 5 c). The ischium of the third maxilliped of P. kisangani sp. nov. from Kisangani (Fig. 5 A) and of P. orbitospinus from Lake Malawi (Fig. 5 C) has a thin but distinct vertical sulcus, whereas this sulcus is faint and obscure in P. amosae sp. nov. from Lake Kivu (Fig. 5 B) and the Malagarasi River (Reed & Cumberlidge 2006: pl. 5 c – d). The chela dactylus (moveable finger) and fixed finger (pollex of propodus) of P. kisangani sp. nov. from Kisangani (Fig. 6 A – B) are both elongated and slender, whereas the chela fingers in P. amosae sp. nov. from Lake Kivu (Fig. 6 C – D) and from the Malagarasi River (Fig. 6 E – F; Reed & Cumberlidge 2006: pl. 5 a figs 46 – 47; NMU TRW 1972.04), and in P. orbitospinus from Lake Malawi (Fig. 6 G – H), are thick and broad. The major chela has 3 large molars at the proximal ends of both fingers, with older specimens showing fusion of these teeth into a flat surface of the fixed finger in P. kisangani sp. nov. from Kisangani (Figs 6 A – B, 8 A) and in P. amosae sp. nov. from the Malagarasi River (CW 80.1 mm) (Fig. 6 E – F; Reed & Cumberlidge 2006: pl. 5 a figs 46 – 47), whereas the proximal parts of both fingers of the major chela in P. orbitospinus from Lake Malawi (Fig. 6 G – H) has enlarged, rounded, separate (unfused) teeth. The P 5 carpus, propodus, and dactylus of P. orbitospinus from Lake Malawi (Figs 10 B, 13) are all elongated and slender, whereas these ambulatory leg articles in P. kisangani sp. nov. from Kisangani (Fig. 8 A – B) and of P. amosae sp. nov. from Lake Kivu (Fig. 9 A – B) and the Malagarasi River (Reed & Cumberlidge 2006: pl. 5 a) are all short and stocky. The G 1 TA in P. kisangani sp. nov. from Kisangani (Fig. 11 A) and P. amosae sp. nov. from Lake Kivu (Fig. 11 B – D, F) and the Malagarasi River (Reed & Cumberlidge 2006: pl. 5 c – d fig. 152) is only slightly widened by a low dorsal lobe and the TA ends in either a straight, or only slightly upcurved tip. This contrasts with the G 1 TA in P. orbitospinus from Lake Malawi, which is conspicuously widened by a high, rounded dorsal lobe (as wide as the TA width at the TA-SA junction) and the G 1 TA ends in a strongly curved upwards tip (Fig. 12 A – H).	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFBEFFE4B5695504FBA0D247.taxon	description	urn: lsid: zoobank. org: act: 1 B 3001 B 9 - 7101 - 4551 - AE 46 - 2 BEFCAD 3598 A Figs 3, 4 C – D, 5 B, 6 C – F, 7 C, 9, 11 B – F, 14, Table 1	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFBEFFE4B5695504FBA0D247.taxon	diagnosis	Diagnosis Exorbital tooth large forward-pointing spine; lateral margin of exorbital tooth lined by granules before meeting postfrontal crest; epibranchial tooth small, granular, followed by small granules lining anterolateral margin (Fig. 4 C – D). Anterolateral margin posterior to epibranchial tooth curving strongly outward (Fig. 4 C – D); postfrontal crest distinct, completely traversing carapace between epibranchial teeth; posterior surface of carapace with deep urogastric grooves; third maxilliped ischium smooth (either lacking vertical sulcus or with faint sulcus); thoracic sternal sulcus S 3 / 4 faint, shallow (Fig. 9 B); major chela fixed finger with 3 large molars proximally, fused in older specimens into flat surface (Figs 6 A – B, 8 A); cheliped carpus inner margin with two large, subequal, forward-pointing spines (Fig. 7 C); cheliped merus inner lower margin with spine-like tooth distally; P 5 carpus, propodus, and dactylus not elongated (Fig. 9 A – B); G 1 TA (Fig. 11 C – F) slightly widened by slim dorsal lobe (⅓ TA width at TA-SA junction); tip straight, only slightly curved upwards.	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFBEFFE4B5695504FBA0D247.taxon	etymology	Etymology The new species is named to honour the memory of Marilyn Suzanne Amos, of Mobile, Alabama, USA, who passed away during these studies. She was the mother of the second author (EJ). The specific epithet is used as a Latin noun in apposition. The vernacular name is Amos’s crab.	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFBEFFE4B5695504FBA0D247.taxon	materials_examined	Material examined Holotype DEMOCRATIC REPUBLIC OF THE CONGO • ♂ subadult; Idjwi Island, Lake Kivu; 2.082854 ° S, 29.071167 ° E; Feb. 1939; A. Loveridge leg.; MCZ CRU- 11224. Other material DEMOCRATIC REPUBLIC OF THE CONGO • 1 ♂ subadult (CW 46.5 mm); Lake Kivu; donated by Royal Belgian Institute of Natural Sciences, Brussels; NHMUK 2020.3 • 1 ♂ subadult (CW 44.5 mm); Goma, Lake Kivu; 30 Nov. 1952; I. Gordon leg.; wide coast; NHMUK 2020.4. RWANDA • 1 ♂ juv. (CW 30.0, CL 23.7, CH 11.2, FW 9.8 mm); Gisenye, Lake Kivu; Mar. 1936; J. C. Bequaert leg.; MCZ CRU- 9177 • 1 ♀ juv. (CW 26.9 mm); Gisenye, Lake Kivu; 12 May 1955; Smithsonian-Bredin Congo Exped., W. L. Schmitt leg.; in water at shoreline; USNM 98937 • 1 ♀ adult (CW 62 mm); Kalemie (formerly Albertville), Lake Tanganyika; 8 Mar. 1919; M. Dhont de Bie leg.; NHMUK 1919.3.8.1 - 3. TANZANIA • 1 ♂ subadult (CW 39.5 mm); Mungonya River, Mwandiga, near Kigoma; 4.828819 ° S, 29.666191 ° E; Apr. 1971; T. R. Williams leg.; NMU TRW 1971.05 • 1 ♀ adult (CW 80.1 mm); Malagarasi River, Uvinza, Kigoma District; 5.115673 ° S, 30.380144 ° E; Apr. 1971; T. R. Williams leg.; NMU TRW 1971.15.	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFBEFFE4B5695504FBA0D247.taxon	description	Description Carapace height equal to front width (CH / FW 1.0); carapace length 2.4 × front width (CL / FW 2.5); carapace width ~ 3 × front width (CW / FW 3.1); posterior region of carapace with deep urogastric grooves; exorbital tooth large forward-pointing spine; lateral margin of exorbital tooth lined by small granules; epibranchial tooth small, granular, followed by large granules lining anterolateral margin (Fig. 4 C – D); anterolateral margin posterior to epibranchial tooth curving strongly outward (Fig. 4 C – D); postfrontal crest distinct, completely traversing carapace between epibranchial teeth; posterior surface of carapace with deep urogastric grooves; carapace branchiostegal wall divided by pleural (vertical) suture into suborbital region (with granules on surface), subhepatic region (with granules, crinae on surface); divided by epimeral (longitudinal) suture; pterygostomial region with granules on surface (Fig. 5 B). Epistomial tooth prominent, granulated, V-shaped. Mandible palp comprising 2 articles; terminal article single, undivided, with setae (but no hard flap) at junction between articles. Third maxillipeds filling entire oral field, except for transversely ovate respiratory openings at superior lateral corners; exopod with long flagellum; third maxilliped ischium smooth (either lacking vertical sulcus or with faint sulcus). Thoracic sternal sulcus S 3 / 4 faint, shallow; episternal sulci S 4 / E 4, S 5 / E 5, S 6 / E 6, and S 7 / E 7 faint. Major chela dactylus (moveable finger) and pollex of propodus (fixed finger) thick, broad, leaving long thin interspace between fingers when closed; both fingers with 3 large teeth proximally, other teeth small unfused distally; major chela fixed finger proximal molars fused into flat surface in older specimens from the Malagarasi River (CW 80.1 mm) (Fig. 6 E – F); cheliped carpus inner margin with two large subequal forward-pointing spines (Fig. 7 C); cheliped merus lower margins heavily granulated, inner lower margin with spine-like tooth distally; P 3 longest, P 5 shortest (carpus, propodus, and dactylus not elongated); P 2 – 5 dactyli tapering to pointed tip, each bearing 4 rows of downward-pointing, short, sharp spines. Male pleon slim, triangular, telson narrow triangle with rounded apex, pleomeres Al – 6 quadrate. G 1 TA proximal third straight, not widened, margins parallel, at midpoint bent sharply outward at 60 ° angle to longitudinal axis of G 1 SA; G 1 TA (Fig. 11 B – E) widened by low dorsal lobe (⅓ TA width at TA-SA junction); tip straight, only slightly upcurved. G 1 SA at junction with G 1 TA with horizontal margin on ventral side, U-shaped indentation filled by conspicuous dorsal membrane on dorsal side. G 2 TA long, flagellum-like (Fig. 11 F). Margins of G 1 TA, SA lined by setae. Size Large species, adult size range between CW 50 to 80 mm. Colour Preserved specimens are uniformly light brown like the holotype, but the large adult female from the Malagarasi River in Tanzania has black pigmentation on both fingers of the chelae (Fig. 6 E – F).	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFBEFFE4B5695504FBA0D247.taxon	distribution	Distribution Potamonautes amosae sp. nov. was collected from rocky areas of Lake Kivu in the D. R. Congo and Rwanda (Fig. 3). Lake Kivu is a relatively small (100 km long by 50 km wide), deep lake (depth 480 m) situated in the Albertine Rift of the Western Rift Valley. This lake is divided by the border between the D. R. Congo and Rwanda, with the large Idjwi Island lying in the D. R. Congo. The Ruzizi River drains south out of Lake Kivu and links it to the northern part of Lake Tanganyika in Burundi, but this species has not been recorded from this river. Potamonautes amosae sp. nov. is found along the eastern shores of Lake Tanganyika in localities associated with the Malagarasi River in western Tanzania (Capart 1952; Reed & Cumberlidge 2006; M. Mbalassa & S. Marijnissen pers. com.) where it flows through the Kigoma District, and on the western shores of Lake Tanganyika at Kalemie in the D. R. Congo (Capart 1952).	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFBEFFE4B5695504FBA0D247.taxon	biology_ecology	Ecology Little is known about the habitat and ecology of P. amosae sp. nov. In the region of Lake Tanganyika this species was often captured in marshes and wetlands near the lake, but never in the lake itself (Capart 1952). In Lake Kivu this species is found on islands in the lake as well as in the lake (Chace 1942). The range of P. amosae sp. nov. includes part of the Lake Victoria Basin Freshwater Ecoregion (FEOW # 521) (Thieme et al. 2005; Abell et al. 2008).	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFBEFFE4B5695504FBA0D247.taxon	conservation	Conservation status An IUCN extinction risk assessment of P. amosae sp. nov. has not yet been carried out. This species has a wide distributional range (with an estimated extent of occurrence (EOO) of almost 46 600 km 2) and has been recorded from seven localities (Fig. 3) in three different countries. Given that there are no known immediate threats to this species, it would probably be assessed as Least Concern.	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFBEFFE4B5695504FBA0D247.taxon	discussion	Remarks There are a number of characters that distinguish P. amosae sp. nov. from P. orbitospinus in Lake Malawi. For example, the male thoracic sternal sulcus S 3 / 4 of P. amosae sp. nov. is faint and shallow (vs deep and complete in P. orbitospinus); the low dorsal lobe of the G 1 TA of P. amosae sp. nov. means that it is only slightly widened (vs a G 1 TA dorsal margin that is conspicuously widened by a high dorsal lobe in P. orbitospinus); the anterolateral margin of P. amosae sp. nov. is lined by small granules (vs lined by a row of small distinct teeth in P. orbitospinus); the merus, propodus, and dactylus of P 5 of P. amosae sp. nov. are all short (vs all elongated and slender in P. orbitospinus); and the third maxilliped ischium of P. amosae sp. nov. is smooth (vs with a third maxilliped ischium that has a deep vertical sulcus in P. orbitospinus). In the past, P. amosae sp. nov. from Lake Kivu has been identified as P. lirrangensis s. lat. by a number of authors (Chace 1942; Bott 1955; Reed & Cumberlidge 2006; Cumberlidge & Meyer 2011). These identifications were made based on characters shared with the type of P. lirrangensis s. str. from Liranga (such as denticles or granules lining the anterolateral margin, 2 large pointed spines on the cheliped carpus inner margin, and a large pointed spine on the cheliped merus inner margin). There are a number of illustrations of P. amosae sp. nov. available, but most of these specimens have been identified as P. lirrangensis s. lat. For example, Chace (1942) illustrated the carapace and G 1 of a specimen from Lake Kivu (MCZ CRU- 11224), and Capart (1952: fig. 12) figured an entire specimen from Kalemie (formerly Albertville) on the western shores of Lake Tanganyika and remarked on its similarity to the species found in Lake Kivu. Later, Reed & Cumberlidge (2006: figs 41 – 51, 153 – 154, 177 pl. V) described in detail an adult female (CW 81 mm) and male (CW 56.5 mm) of P. lirrangensis s. lat. (NMU TRW 1971.15) from the Malagarasi River at Uvinza in the Kigoma District of Tanzania near Lake Tanganyika. DNA sequence data are available from specimens formerly assigned to P. lirrangensis s. lat. from Lakes Kivu, Tanganyika, and Malawi (Marijnissen et al. 2006; Daniels et al. 2015; Kochey et al. 2017). Marijnissen et al. (2006) used 2 mitochondrial DNA sequence markers (12 S rRNA and 16 S rRNA) to investigate relationships between specimens identified morphologically as P. lirrangensis s. lat. from Ruzizi in Lake Kivu in the D. R. Congo (GenBank DQ 203210, DQ 203236), from Uazua in the Zambian part of Lake Tanganyika (DQ 203211, DQ 203237), and from Thumbi West Island near Cape Maclear in southern Lake Malawi (GenBank DQ 203209, DQ 203235). Marijnissen et al. (2006: fig. 1) found that the specimen from Lake Kivu (here recognised as P. amosae sp. nov.) formed a separate basal lineage from the clade formed by the other 2 specimens from Lake Malawi (here recognised as P. orbitospinus). Daniels et al. (2015) sequenced four DNA markers (GenBank AY 803494, AY 803534, AY 803568, AY 803682) for a specimen (ZMA. Crust. De. 204681) held in the NBL that was identified in that work as P. lirrangensis s. lat. and incorrectly listed as being from Lake Malawi. In fact, specimen ZMA. Crust. De. 204681 was collected from Lake Kivu (site 13, E. major; 23 Aug. 2002; Pascal Isumbisa leg.) and is therefore properly identified as P. amosae sp. nov. There is molecular support for the recognition of P. amosae sp. nov. as a valid species from mitochondrial 16 S rRNA and the nuclear coding gene Histone H 3 sequences (Fig. 14). Across the 2 genes, 5 specimens are assigned to P. amosae sp. nov.: 3 from Uvinza, Kigoma District, Tanzania (2016 - 07 - 08 - UV 1; 2016 - 07 - 08 - UV 2; 2016 - 07 - 08 - UV 3), and two from Lake Kivu. The first specimen from Lake Kivu is ZMA. Crust. De. 204681 represented by AY 803534 and AY 803682 (Daniels et al. 2015); the second specimen is from Ruzizi, Lake Kivu represented by DQ 203236 (Marijnissen et al. 2006).	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFBAFFEFB6F55694FB4BD172.taxon	description	Figs 2, 4 E, 5 C, 6 G – H, 7 D, 10, 12 – 14, Table 1	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFBAFFEFB6F55694FB4BD172.taxon	description	Common name The Malawi blue crab.	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFBAFFEFB6F55694FB4BD172.taxon	diagnosis	Diagnosis Exorbital tooth large forward-pointing spine; lateral margin of exorbital tooth not angled, in line with midline axis of carapace curving slightly inward (concave) before meeting postfrontal crest; epibranchial tooth pointed, as large as other teeth lining anterolateral margin (Fig. 4 E). Anterolateral margin posterior to epibranchial tooth curving strongly outward (Fig. 4 E); postfrontal crest distinct, completely traversing carapace between epibranchial teeth; posterior surface of carapace with deep urogastric grooves; third maxilliped ischium with thin, deep vertical sulcus; thoracic sternal sulcus S 3 / 4 deep, V-shaped, completely traversing sternum (Fig. 10 B); cheliped carpus inner margin with two large, subequal, forward-pointing spines (Fig. 7 D); cheliped merus inner lower margin with spine-like tooth distally; P 5 carpus, propodus, and dactylus all slender, distinctly elongated; G 1 TA (Fig. 12 A – C, E – G,) conspicuously widened by high, rounded dorsal lobe (as wide as TA width at TA-SA junction); tip distinctly curved upwards.	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFBAFFEFB6F55694FB4BD172.taxon	materials_examined	Material examined Lectotype (here designated) MALAWI • ♂ adult (CW 56.9, CL 38.4, FW 13.8 mm); western shore of Lake Malawi; 31 Jan. 1908; Tanganyika Exped., J. E. S. Moore leg.; NHMUK 1908.1.31.27. Paralectotypes MALAWI • 3 juvs (including CW 33.2, CL 22.8, CH 11.6, FW 10.0 mm); Lake Malawi; 19 Dec. 1891; M. Woodward leg.; NHMUK 1891.12.19.1 to NHMUK 1891.12.19.3 • 1 ♂ subadult (CW 27.5 mm); Universities Mission, Likoma, Lake Nyassa (now Lake Malawi); 14 Jan. 1893; J. A Williams leg.; NHMUK 1893.1.14 • 1 ♀ adult (CW 52.8 mm); west coast of Lake Malawi from Nkhata Bay to Ruarwe; Jun. 1896; A. Whyte leg.; NHMUK 1897.4.29.1 • several subadults; Nkhata Bay, Lake Malawi; 23 Jun. 1904; Third Tanganyika Exped., local fishermen and Dr W. A. Cunnington leg.; NHMUK 1897.4.29.23. Additional material MALAWI • 2 ♀♀ adults (CW 61.1, 65.8 mm), 2 ♀♀ subadults (CW 36.7, 45.1 mm), 1 ♂ subadult (CW 36.6 mm), 9 juvs; Lake Malawi, N of Hudzi; 20 Oct. 1926; Cristy leg.; NHMUK 1926.10.20.1 to NHMUK 1926.10.20.5 • 1 ♂ subadult (CW 31.1 mm); NW coast of Lake Malawi, near Nkhata Bay; 31 Jan. 1908; NHMUK 1908.1.31.16 - 18 • 1 ♀ adult (CW 55.6 mm); Lake Malawi, Monkey Bay; 20 Oct. 1926; NHMUK 1926.10.20.6 • 1 ♂ subadult (CW 49 mm), 1 ♀ adult with hatchlings (CW 64.8 mm); NW coast of Lake Malawi, near Nkhata Bay; 26 Jul. 1954; Miers leg.; NHMUK 1954.7.26.5, NHMUK 1954.7.26.6 • 1 ♀ adult (CW 61.1 mm), 1 ♂ adult (CW 55.4 mm); Lake Malawi; 5 Jun. 1956; G. Fryer leg.; NHMUK 1956.6.5.10, NHMUK 1956.6.5.11 • 1 ♀ adult (CW 57 mm), 1 ♂ subadult (CW 40 mm), 2 juvs (CW 32.5, 33.4 mm); Lake Malawi; 26 Jul. 1954; W. A. Cunnington leg.; NHMUK 1954.7.26.3, NHMUK 1954.7.26.4 • 1 ♂ subadult (CW 51.1 mm); Lake Malawi, Monkey Bay; Mar. 1968; D. H. Eccles leg.; among rocks in sand; NMU TRW 1972.04 • 1 ♂ subadult (CW 46.2 mm); Lake Malawi, 2 km ENE of Monkey Bay; May 1968; D. H. Eccles leg.; NMU TRW 1972.05 • 1 ♀ subadult (CW 51.1 mm); Lake Malawi; Sep. 1988; Irv. Kornfield leg.; NMU 09.1988 k. 1 • 1 ♀ (damaged); Lake Malawi, N of Monkey Bay; 5 Apr. 1972; D. H. Eccles leg.; depth 91 m; NMU TRW 1972.02 • 1 ♂ (CW 51.4 mm); Lake Malawi, Monkey Bay; 24 Mar. 1968; D. H. Eccles leg.; among rock in sand with little vegetation; NMU TRW 1972.04 • 1 ♂ (CW 46.5 mm); Lake Malawi, ENE of Monkey Bay; 23 May 1968; D. H. Eccles leg.; NMU TRW 1972.05 • 1 ♂ subadult (CW 46.5 mm); Lake Malawi, Cape Maclear; M. Genner leg.; NHMUK 2010 - 06 - CM-CM 6 • 1 ♀ subadult (CW 50.15 mm); same collection data as for preceding; NHMUK 2010 - 06 - CM-CM 8 • 1 ♀ adult (CW 52.2 mm); same collection data as for preceding; Jun. 2010; NHMUK CM 13 • 1 ♀ adult (CW 54.4 mm); same collection data as for preceding; NHMUK CM 14 • 1 ♀ subadult (CW 44.1 mm); same collection data as for preceding; NHMUK CM 21 • 1 ♀ adult (CW 54.8 mm); Lake Malawi, NW coast near Nkhata Bay; 1961; Sweeney leg.; NHMUK 2011.1509 • 1 ♀ subadult (CW 32.7 mm); Lake Malawi, Cape Maclear; 17 Jun. 2010; M. Genner leg.; UB CM 17 • 1 ♀ subadult (CW 37.4 mm), 1 ♀ adult (CW 57.6 mm); 2 ♂♂ adults (CW 55.1, 54.9 mm); same collection data as for preceding; UB CM 22, UB CM 11, UB CM 20, UB CM 12 • 1 ♀ adult (CW 57.1 mm), 1 ♀ subadult (CW 33.1 mm); same collection data as for preceding; 26 Jun. 2010; UB CM 10, UB CM 5 • 1 ♂ subadult (CW 49.2 mm); same collection data as for preceding; 21 Jun. 2010; UB CM 4 • 1 ♀ subadult (CW 48.3 mm); same collection data as for preceding; UB CM 9 • 1 ♀ subadult (CW 46.7 mm); same collection data as for preceding; UB CM 15 • 1 ♀ subadult (CW 35.4 mm); same collection data as for preceding; UB CM 16 • 1 ♀ subadult (CW 45.4 mm); same collection data as for preceding; UB CM 24 • 1 ♂ adult (CW 59.4 mm); same collection data as for preceding; UB CM 7 • 2 ♀♀ adults (CW 55.4, 54.4 mm), 2 ♀♀ subadults (CW 44.9, 45.9 mm); same collection data as for preceding; UB CM 7 • 1 ♂ adult; same collection data as for preceding; 26 Jun. 2010; R. Bills leg.; AMG CAW 467 A.	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFBAFFEFB6F55694FB4BD172.taxon	description	Redescription Carapace height equal to front width (CH / FW 1.0); carapace length 2.5 × front width (CL / FW 2.5); carapace width 3.5 × front width (CW / FW 3.5); exorbital tooth large forward-pointing spine; exorbital tooth lateral margin not angled, in line with midline axis of carapace, curving slightly inward (concave) before meeting postfrontal crest; epibranchial tooth pointed, as large as other teeth lining anterolateral margin (Figs 4 E, 10 A). Anterolateral margin posterior to epibranchial tooth curving strongly outward (Fig. 4 E); postfrontal crest distinct, completely traversing carapace between epibranchial teeth; posterior surface of carapace with deep urogastric grooves; carapace branchiostegal wall divided by vertical pleural suture into suborbital and subhepatic regions, both smooth with sparse granules, pterygostomial region smooth (Fig. 10 B); epistomial tooth prominent, granulated, V-shaped. Mandible palp comprising 2 articles; terminal article single, undivided, with setae (but no hard flap) at junction between articles. Third maxillipeds filling entire oral field, except for transversely ovate respiratory openings at superior lateral corners; exopod with long flagellum; ischium with deep vertical sulcus. Thoracic sternal sulcus S 3 / 4 deep, completely traversing sternum; episternal sulci S 4 / E 4, S 5 / E 5, S 6 / E 6, and S 7 / E 7 distinct. Major chela dactylus (moveable finger) and pollex of propodus (fixed finger) thick, broad, leaving long interspace between fingers when closed; both fingers with 3 large teeth unfused proximally, several medium-sized teeth distally (Fig. 6 G – H); cheliped carpus inner margin with two large subequal forwardpointing spines (Fig. 7 D); cheliped merus inner lower margin with spine-like tooth distally; P 5 carpus, propodus, and dactylus all slender, distinctly elongated; P 2 – 5 dactyli elongated, tapering to pointed tip, each bearing 4 rows of downward-pointing, short, sharp spines. Pleon of male slim, triangular, telson narrow triangle with rounded apex, pleomeres Al – 6 quadrate. G 1 TA proximal third straight, not widened, margins parallel, at midpoint bent sharply outward at 90 ° angle to longitudinal axis of G 1 SA; G 1 TA (Fig. 12 A – C, E – G) conspicuously widened by high, rounded dorsal lobe (as wide as TA width at TA-SA junction); tip distinctly curved upwards; G 1 SA at junction with G 1 TA with horizontal margin on ventral side, U-shaped indentation filled by conspicuous dorsal membrane on dorsal side. G 2 TA: long, flagellum-like (Fig. 12 D, H). Margins of G 1 TA, SA lined by setae. Size Large species, pubertal molt starting around CW 53 mm (largest adult male CW 56.9 mm, largest adult female CW 53.9 mm). Colour The carapace surface and branchiostegal walls of living specimens are deep blue, and are especially bright in newly-hardened specimens (Fig. 13). There are distinct white outlines marking the postfrontal crest, anterolateral margins, frontal margin, orbital margins, exorbital teeth, epistome, and the third maxilliped ischium and merus. The thoracic sternum is pinkish blue / grey and cream, and the arthrodial membranes on the inner side of the joints between the coxae and the basis of the chelipeds and P 2 – 5 are cream.	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFBAFFEFB6F55694FB4BD172.taxon	distribution	Distribution Potamonautes orbitospinus is abundant and widely distributed throughout Lake Malawi (Fig. 2) and has not been recorded from outside of the lake.	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFBAFFEFB6F55694FB4BD172.taxon	biology_ecology	Ecology Lake Malawi is the southernmost Great Lake in the East African Rift system and lies in 3 countries: Malawi, Mozambique, and Tanzania. The Ruhuhu River in Tanzania flows west into the northeastern part of Lake Malawi while the Shire River drains south out of the lake and is a tributary of the Zambezi River. In 1904, Cunnington and his assistants collected the first known specimens of P. orbitospinus from the waters of Lake Malawi itself, noting that some specimens were found on the beach (Cunnington 1907). The specimens reported on here are all restricted to Lake Malawi, and this species is a lake specialist that has never been collected in the rivers of the drainage basin that flow into the lake.	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFBAFFEFB6F55694FB4BD172.taxon	conservation	Conservation status An IUCN conservation assessment of P. orbitospinus has not yet been carried out. The species is known from a large number of specimens from 16 localities all in Lake Malawi (29 600 km 2). Given that its estimated extent of occurrence (EOO) is more than 21 100 km 2, and that no specific threats are known, it would probably be assessed as Least Concern. It is significant that the population levels of P. orbitospinus are sufficient to be regularly caught as bycatch in local fisheries in Lake Malawi, and this species is also captured to supply a steady demand by the global aquarium trade.	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
03C787B8FFBAFFEFB6F55694FB4BD172.taxon	discussion	Remarks The recognition of P. orbitospinus and P. lirrangensis s. str. as valid species returns to the original taxonomic situation over 110 years ago when they were first described from two widely separated locations (Rathbun 1904; Cunnington 1907). Chace (1942) also treated P. lirrangensis and P. orbitospinus as valid species, but Bott (1955), Reed & Cumberlidge (2006) and Cumberlidge & Meyer (2011) considered Potamon (Potamonautes) orbitospinus to be a junior synonym of Potamonautes lirrangensis s. lat. The result has been that the available descriptions and distribution maps of Potamonautes lirrangensis s. lat. (Reed & Cumberlidge 2006: fig. 177) incorrectly combine characters and localities of P. lirrangensis s. str. from the Congo River with those of P. orbitospinus from Lake Malawi, and P. amosae sp. nov. from Lake Kivu and Kigoma District near Lake Tanganyika. Potamonautes orbitospinus is recognised here based on characters of the lectotype described by Cunnington (1907) from Lake Malawi as well as other comparable material from this lake. The redescription includes new taxonomically important characters because although the description by Cunnington (1907) of P. orbitospinus was based on an adult male, he did not illustrate the first gonopod or sternal characters of the type specimen. See concluding remarks below for comparisons with other superficially similar species. The combined phylogeny based on mitochondrial 16 S rRNA and the nuclear coding gene Histone H 3 (Fig. 14) includes a specimen from Thumbi West Island near Cape Maclear in southern Lake Malawi (GenBank DQ 203209, DQ 203235), alongside eight other specimens from Cape Maclear and Chiofu on the east coast of Lake Malawi. The phylogeny suggests a monophyletic clade for P. orbitospinus from Lake Malawi, separate from the clade for P. amosae sp. nov. (Fig. 14). A specimen identified as P. lirrangensis s. lat. from ‘ Uazua’ in the Zambian part of Lake Tanganyika (POlirrangensisZAM 31; Marijnissen et al. 2006) has a partial 16 S sequence (DQ 203237) with high similarity (99 %) to a specimen of P. orbitospinus from Lake Malawi (POlirrangensisMAL 27; DQ 203235; Marijnissen et al. 2006). This same specimen (POlirrangensisZAM 31), however, has a partial 12 S sequence (DQ 203211) which has only 97 % similarity to POlirrangensisMAL 27 (DQ 203209). This may indicate that P. orbitospinus shares a close evolutionary affinity to specimens within Lake Tanganyika, but further sampling is required to determine the evolutionary relationships of these two groups. Kochey et al. (2017) carried out a molecular study of the Malawi blue crab (which they identified as P. lirrangensis s. lat.) that found the morphologically similar populations in Lake Malawi to be equally close genetically, and confirmed that the lake hosts only a single species of freshwater crab (here identified as P. orbitospinus). Those authors also found that the blue crab populations in Lake Malawi had only moderate haplotype diversity and low levels of nucleotide diversity for two mitochondrial loci (NADH dehydrogenase subunit 1 (ND 1) and cytochrome b (CytB) (Kochey et al. 2017). The lack of divergence of blue crab populations in Lake Malawi and the morphological similarity of specimens found in different parts of the lake suggests a recent colonisation (Kochey et al. 2017).	en	Cumberlidge, Neil, Johnson, Emily, Clark, Paul F., Genner, Martin J. (2021): Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species. European Journal of Taxonomy 744 (1): 145-178, DOI: 10.5852/ejt.2021.744.1309, URL: http://dx.doi.org/10.5852/ejt.2021.744.1309
