Arcopotamonautes itamba Cumberlidge & Genner, 2025

Arcopotamonautes itamba Cumberlidge & Genner View in CoL sp. n.

( Figures 1 View Figure 1 , 3–8 View Figure 3 View Figure 4 View Figure 5 View Figure 6 View Figure 7 View Figure 8 ; Tables 1, 3)

Material examined

Type material. Holotype: TANZANIA: adult ♂ (CW 55.6 mm), Itamba Crater Lake , Mbeya District (033.8427⁰E, 824 m ASL), coll. M. J. Genner, 19 July 2011 ( NHMUK 2018.308 About NHMUK ).

Paratypes: TANZANIA: subadult ♂ (CW 41.1 mm) Itamba Crater Lake , Mbeya District (033.8427⁰E, 824 m ASL), coll . M . J . Genner, 19 July 2011 ( NHMUK 2018.307 About NHMUK ) ;

TANZANIA: subadult ♂ (CW 46.3 mm), Itamba Crater Lake, Mbeya District (09.3522⁰S, 033.8427⁰E

ASL), coll . M . J . Genner, 19 July 2011 ( NHM 2018.314 ); TANZANIA: 2 subadult ♂♂ (CW 47.8 mm 2025.1169; 31.4 mm, NHMUK 2025.1170 About NHMUK ), subadult ♀ (CW 23 mm) ( NHMUK 2025.1168 About NHMUK ) Itamba Crater Mbeya District (09.3522⁰S, 033.8427⁰E, 824 m ASL), coll . M . J. Genner, 22 November 2011;

subadult ♀ (CW 44.4 mm), Itamba Crater Lake, Mbeya District (09.3522⁰S, 033.8427⁰E, 824 m ASL

M. J. Genner, 19 July 2011 ( NHMUK 2018.315 About NHMUK ) .

Other material. TANZANIA: adult ♀ (CW 61 mm), Kyungululu Crater Lake , Mbeya District, coll . M. J.

18 July 2011 ( NHMUK 2018.324 About NHMUK ); TANZANIA: adult ♂ CW 56.8 mm, Kyungululu Crater Lake , Mbeya (09.308⁰S, 033.8655⁰E, 927 m ASL), coll . M . J . Genner, 18 July 2011 ( NHM 2018.310 ); TANZANIA: adult

54.0 mm), Kyungululu Crater Lake (09.308⁰S, 033.8655⁰E), coll . M . J . Genner, 18 July 2011 ( NHMUK TANZANIA: adult ♀ (CW 51.6 mm, NHMUK 2025.1212 About NHMUK ) Itamba Crater Lake , Mbeya District (033.8427⁰E, 824 m ASL), coll . M . J . Genner, July 2011; TANZANIA: 13 adult ♂♂ (CWs in mm): 58.3 (2025.1189), 57.3 ( NHMUK 2025.1206 About NHMUK ), 56.4 ( NHMUK 2025.1208 About NHMUK ), 56.2 ( NHMUK 2025.1213 About NHMUK ), 54.6 (2025.1192), 54.5 ( NHMUK 2025.1182 About NHMUK ), 53.2 ( NHMUK 2025.1198 About NHMUK ), 53.1 ( NHMUK 2025.1186 About NHMUK ), 51.9 (2025.1210), 51.4 ( NHMUK 2025.1205 About NHMUK ),49.0 ( NHMUK 2025.1199 About NHMUK ), 48.6 ( NHMUK 2025.1201 About NHMUK ), 7 subadult (CWs 46.3, 45.0, 44.5, 43.4, 43.36, 43.1, 39.0 mm), 17 adult ♀♀ (CWs in mm): 58.9 ( NHMUK 2025.1176 About NHMUK

HISTORY

( NHMUK 2025.1193), 49.6 ( NHMUK 2025.1209 About NHMUK ), 49.3 ( NHMUK 2025.1174 About NHMUK ), 47.3 ( NHMUK 2025.1194 About NHMUK District ( 09.3522°S, 033.8427°E), coll. M. J. Genner, 19 July 2011; TANZANIA: 1 specimen, subadult 38.0 mm, NHMUK 2025.1239 About NHMUK ) Itupi East stream ( 09.31°S, 033.77°E, 1,116 m ASL), coll GoogleMaps . G GoogleMaps . Turner , 2 July TANZANIA: 1 specimen, Kyungululu Crater Lake ( 09.308°S, 033.866°E), coll GoogleMaps . M GoogleMaps . J . Genner , 18 July TANZANIA: subadult ♀ (CW 31.0 mm), Masoko Crater Lake ( 09.332°S, 033.756°E, 861 m ASL M. J. Genner ( July 2018) ( NHMUK 2025.1240 About NHMUK ); TANZANIA: adult ♂ (CW 52.0 mm, NHMUK subadult ♀ (CW 40.1 mm, NHMUK 2025.1217 About NHMUK ), Nkokwa ( 09.520°S, 033.785°E, 522 m ASL P. N. Gabagambi, 20 November 2020; TANZANIA: 2 subadult ♂♂ (CW 45.2 mm ( NHMUK GoogleMaps

31.9 mm ( NHMUK 2025.1223 About NHMUK ), 4 subadult ♀♀ (CW 45.9 mm ( NHMUK 2025.1218 About NHMUK ), 37.1 mm (2025.1220), 33.2 mm ( NHMUK 2025.1219 About NHMUK ), 31.9 mm ( NHMUK 2025.1222 About NHMUK ), Nguwesi River ( 033.827°E, 568 m ASL), coll . P . N . Gabagambi, 20 November 2020; TANZANIA: adult ♀ (CW ( NHMUK 2025.1225 About NHMUK ), 5 subadult ♂♂ (CWs 48.0 mm ( NHMUK 2025.1230 About NHMUK ), 39.0 mm ( NHMUK

44.0 mm ( NHMUK 2025.1229 About NHMUK ), 36.4 mm ( NHMUK 2025.1227 About NHMUK ), 35.0 mm ( NHMUK 2025.1228 About NHMUK ), 3 subadult (CWs 41.6 mm ( NHMUK 2025.1226 About NHMUK ), 40.0 mm ( NHMUK 2025.1232 About NHMUK ), 38.0 mm ( NHMUK 2025.1224 About NHMUK ) River ( 09.363°S, 033.853°E, 763 m ASL), coll GoogleMaps . P GoogleMaps . N. Gabagambi, 19 November 2020. ZAMBIA: 4 juveniles 14.0 mm ( NHMUK 2025.1233 About NHMUK ), 22.0 mm ( NHMUK 2025.1234 About NHMUK ), 18.0 mm ( NHMUK 2025.1235 About NHMUK ), ( NHMUK 2025.1236 About NHMUK ) Chilonga ( 12.16°S, 031.232°E, 1,390 m ASL), coll GoogleMaps . M GoogleMaps . J . Genner, 17 June 2010; subadult ♂ (CW 24.0 mm ( NHMUK 2025.1238 About NHMUK ), juvenile (CW 18.0 mm ( NHMUK 2025.1237 About NHMUK ), Kaombe ( 030.769°E, 1,549 m ASL), coll. M. J. Genner, 17 June 2010.

Diagnosis

Exorbital tooth small, low; epibranchial tooth rounded, granular; anterolateral carapace margin small granules ( Figure 4 View Figure 4 (a,b)); carapace lateral margin behind epibranchial tooth lined by small margin curving strongly inward posteriorly over carapace surface ( Figure 4 View Figure 4 (a,b)); postfrontal crest smooth, completely traversing carapace between epibranchial teeth; posterior surface of carapace with urogastric, cardiac grooves; carapace branchiostegite suborbital, subhepatic, pterygostomial smooth; vertical, epimeral sutures marked by small granules ( Figure 5 View Figure 5 (b)); third maxilliped ischium deep vertical sulcus ( Figure 5 View Figure 5 (a)); thoracic sternal sulcus S3/4 deepest at sides, shallow in middle ( Figure 5 View Figure 5 (a)); margins of dactylus, propodus pollex of both chelae lined by distinct rounded teeth large teeth proximally, interspersed by medium-sized rounded teeth (Figure (6(a–c)); cheliped carpus margin distal tooth large, slim, pointed, proximal tooth medium-sized, pointed ( Figure 3 View Figure 3 (a)); cheliped lower margins lined by large granules, distal meral tooth spinelike; P2–5 carpus, propodus, and dactylus elongated ( Figure 6 View Figure 6 (c)). G1TA midpart raised by thin high dorsal crest formed from medial margin of lobe ( Figure 7 View Figure 7 (a,b)), G1TA midpart broadened by wide gutter running between medial, lateral dorsal lobe ( Figure 7 View Figure 7 (d)); G1TA distal third slim; ventral, dorsal lobes both low, tapering to pointed tip ( Figures 7 View Figure 7 (a,b) and 8(a,b,d–f)).

Description

Carapace arched, height greater than front width ( CH /FW 1.3); carapace length 1.5 × carapace width 1.5); exorbital tooth small, low; epibranchial tooth rounded, granular; anterolateral carapace margin small granules ( Figure 4 View Figure 4 (a,b)); carapace lateral margin behind epibranchial tooth lined by small granules, curving strongly inward posteriorly over carapace surface ( Figure 4 View Figure 4 (c,d)); postfrontal crest distinct, completely traversing carapace between epibranchial teeth; posterior surface of carapace with deep cardiac grooves; carapace branchiostegite suborbital, subhepatic, pterygostomial regions all smooth; epimeral sutures marked by small granules ( Figure 5 View Figure 5 (b)). Epistomial tooth prominent, granulated, ( Figure 4 View Figure 4 (b)). Mandibular palp consisting of basis and two articles; terminal article undivided, with hardened ridge along superior margin originating at article junction ( Figure 6 View Figure 6 (d)). Third maxilliped with deep vertical sulcus ( Figure 5 View Figure 5 (a)). Thoracic sternal sulcus S3/4 reduced to two short deep sulci, middle obscure ( Figure 5 View Figure 5 (a)); episternal sulcus S4/E4 obscure, S5/E5, S6/E6, S7/E7 faint, incomplete ( Figure 6 View Figure 6 (b chela dactylus (moveable finger) arched, propodus pollex (fixed finger) thick, broad, leaving ovoid between fingers when closed; margins of dactylus, margins of propodus pollex of both chelae lined by

HISTORY longest, P5 shortest ( Figure 3 View Figure 3 (b)); P2–5 dactyli tapering to pointed tip, each bearing four rows of pointing, short, sharp spines ( Figure 3 View Figure 3 (b)). G1TA length about one-third G1SA length (G1TA/G1SA 0.4), outward at 45° to longitudinal axis of G1SA; G1TA lateral margin lined with short setae; G1TA ventral, dorsal lobes; ventral lobe low, slim, not raised, not widened, extending from G1SA-G1TA

HISTORY of dorsal lobe ( Figure 7 View Figure 7 (d)); G1TA distal third slim; ventral, dorsal lobes both low, tapering to pointed tip ( Figures 7 View Figure 7 (a,b) and 8(a,b,d–f)). G1SA medial margin lined by conspicuous setae, lateral margin with short setae. G1SA ventral side with horizontal margin at G1TA-G1SA junction; G1SA dorsal side with indentation filled by conspicuous dorsal membrane. G2SA long, slim, subequal to G1SA; G2SA widest tapering sharply inward about one-third along length, last two-thirds forming long, thin, tapering, process supporting elongated flagellum-like G2TA (G2TA/G2SA 0.6) ( Figures 7 View Figure 7 (c) and 8(c)).