Figs 92–94, Map 5
Type material. Holotype male from 03º 04’ S 51º 46’ W, Margem Direita do Rio Xingu, Senador José Porfírio, Pará, Brazil, 24.ii.2001 (MPEG 239). Paratypes: BRAZIL. Pará: Senador José Porfírio, Margem Direita do Rio Xingu, 03º 04’ S 51º 46’ W, 1 ♁, 25.ii.2001 (MPEG 240, 244); 1♁, 02.iii.2001 (MPEG 242); 1♁, 04.iii.2001 (MPEG 243); 3♁, 03.iii.2001 (MPEG 245); trilha do Censo, 1 ♁, 23.ii.2002 (MPEG 238).
Etymology. The specific name is a noun in apposition from the type locality name, Rio Xingu.
Diagnosis. Males of A. xingu resemble those of A. vilhena (Fig. 75 A–C), A. harveyi (Fig. 78 A–C), A. itapitocai (Fig. 83 A–C), A. nattereri (Fig. 67 A–C) and A. utinga (Fig. 103 A–C) by the BTA displaced dorsally in relation to a middle longitudinal line along prolateral tegular surface (Fig. 94 A). They r Resemble those of A. vilhena, A. nattereri and A. utinga by the keels being very close to each other, as seen in prolateral view (Fig. 94 A, B) and those of A. vilhena, A. harveyi, A. itapitocai, A. itaqui (Fig. 91 A–C) and A. utinga by PA continuous to PI. They differ from those of all other species of the group nattereri by a prolateral tegular depression above PA on prolateral tegular margin as seen in dorsal view and distal third of reservoir corrugated (Fig. 94 A).
MALE (MPEG 239): Total length 16.38; Carapace, long 7.00; wide 6.25. Carapace rounded. Anterior eye row slightly procurved, posterior row recurved (Fig. 92 B). With one short bristle between AME-clypeus. With one long bristle between ALE–ALP and few short and weak bristles between posterior eyes-fovea and lateral eyesedge of carapace. Sternum with eight sigilla strongly fused medially (Fig. 92 C). Rastellum protuberant, inverted Vshaped, hirsute, without spines apically (Fig. 92 E, F). Chelicerae with seven denticles along prolateral row of teeth. Prolateral row with five megateeth and one tooth on basal part. Retrolateral row with five megateeth and two denticles between three basal megateeth (Fig. 92 D). Patella and tibia III with distal crown of well-developed thorns, not interrupted in middle (Fig. 93 A, B). Patellae III and IV with spines on prolaterodorsal face (Fig. 93 A, C). Tibia IV without spines on dorsal surface (Fig. 93 D). Ventral pseudoscopulae occupying 50% of tarsus I, 70% of II and 100% of III and IV. Pseudoscopula of tarsi I and II with setae spaced, forming diffuse group of bristles; on tarsi III and IV, compact. Carapace, chelicerae, sternum, coxae, trochantera, femora, patellae, tibiae, metatarsi and tarsi reddish brown; abdomen pale gray with dorsal scutum occupying 1/3 of anterior abdomen (Fig. 92 A). Eyes: Diameters: PME 0.36, PLE 0.4, ALE 0.56, AME 0.48; MOQ: Length 1.32, front width 2.96, back width 2.8; Interdistances: PME–PME 1.56, PLE–PME 0.12, AME–AME 0.2, ALE–AME 0.56, ALE–PLE 0.6, AME–PME 0.4. Ocular area: OAL 4.5, OAW 3.75, and IF 2. Body: Clypeus: 0.25; Fovea: 2.62; Labium: long 1.37; wide 1.12; Chelicerae: long 3.5; wide 1.87; Sternum: long 4.37; wide 3.5. Abdomen: long 7.87; wide 5. Leg measurements: I: Fe 6.62/ Pa 3/ Ti 4.25/ Me 4.75/ Ta 2.87/ total 21.5. II: 6.25/ 3/ 3.75/ 5/ 2.87/ 20.87. III: 5.25/ 3.12/ 2.87/ 5.12/ 2.75/ 19.12. IV: 7.25/ 3.25/ 5.75/ 6/ 3.37/ 25.62. Formula 4123. Spination: I—Fe v0, d0, p0, r0; Pa v0, d0, p0, r0; ti v0-0-3, d0, p0, r0; Me v3-3-5, d0, p1-0- 1, r2-6-6; ta v0, d0, p0-3-2, r1-6-4. II—Fe v0, d0, p0, r0; Pa v0, d0, p0, r0; ti v0-2-1, d0, p0, r0-0-2; Me v2-4-2, d0, p0-0-2, r0-4-5; ta v0-0-2, d0, p1-2-4, r1-4-6. III—Fe v0, d0, p0, r0; Pa v0, d3-6-16, p0-0-2, r0; ti v0, d0-0-12, p0- 0-2, r0-0-1; Me v1-0-2, d1-1-2, p1-0-2, r0-2-3; ta v0, d0, p1-3-4, r0-7-4; IV—Fe v0, d0, p0, r0; Pa v0, d11-11-4, p0-0-1, r0; ti v0-0-2, d0, p0, r0; Me v0-1-1, d0, p1-1-3, r0; ta v0, d0, p0-6-9, r0-3-9. Palp: PA well-developed, continuous to PI. Embolus with three keels (PAc, PI and PS). BTA developed, displaced dorsally in relation to middle longitudinal line along prolateral tegular surface; serrated area below PAc with one denticle; embolar base thin and elongated (Fig. 94 A–C).
Distribution. BRAZIL. Pará: Senador José Porfírio (Map 5).