Arrenurus (Megaluracarus) urbanus Ramírez-Sánchez & Rivas, 2013, sp. nov.

Arrenurus (Megaluracarus) urbanus sp. nov.

(FIGURES 1 D, 2D, 3D, 4G–H, 26–32)

Type material. Holotype male from Cuemanco canal, Xochimilco ecological park, Mexico City, 2242 masl, 19º17’20” N 99º06’06” W, 27 October 2001, coll. J. Cime and G. Rivas. Paratypes: Two females (one of them same data as holotype) and two males (CNAC007183), same locality as holotype, 16 December 2001, coll. J. Cime and M. Ramírez-Sánchez.

Diagnosis. Idiosoma margins smooth, cauda moderately long, slightly constricted at its base and proportioned with the anterior idiosoma (Fig. 1 D). Idiosoma and cauda bulky in lateral view (Fig. 2D). P-II medially with a characteristic patch of two types of setae: Needle and snake-shaped (Fig. 28). The idiosoma and appendages intense greenish blue, without pale areas in the integument.

Description. MALE: Idiosoma 693 (729–735) long and 467 (441–473) wide; anterior idiosoma margin rounded (Fig. 1 D). Greatest width of dorsal shield 368 (357–378); dorsal shield length including cauda 609 (620– 646); non-caudal portion bearing the postocularia and three pairs of glandularia, D2 setae well separated from its corresponding glands; D3 setae and glands close to each another and located rostral to its widest portion (Fig. 26). Cauda moderately long in proportion with anterior idiosoma (Fig. 1 D), 189 (210–220) long, slightly constricted at its base, proximal width of cauda 247 (257), distal width of cauda 278 (284); posterior margin rounded and smooth when viewed dorsally; in lateral view, cauda thicker at its base than the anterior idiosoma (Fig. 2D, 27). First coxae with sharp but not projecting anterior corners (Fig. 3 D); second coxae with blunt corners; second and third coxae separated by two rows of body pores; medial margin of third and fourth coxae parallel, with

posterior corner squared; posterior margin of fourth coxae straight. Acetabular plates of moderate size extending straight out from genital opening and reaching posterior angles of fourth coxae; a few hairs on the posterior margin of fourth coxae but they are not visible in dorsal view. Dorsal lengths of palpal segments (Fig. 28): P-I 25 (28–30); P-II 65 (65–69); P-III 43 (33–38); P-IV 68 (65–68); P-V 38 (30–32). P-II medial bears a patch of numerous long needle-shaped setae and four snake-shaped setae; P-IV distoventral portion angular, with a relatively large antagonistic seta, 28 in length. Dorsal lengths of distal segments of first leg (Fig. 29): I-Leg-4 94 (90–93); I-Leg-5 90 (93–95); I-Leg-6 120 (125–138). Dorsal lengths of distal segments of fourth leg (Fig. 30): IV-Leg-4 120 (125), 170 (178) to tip of distal extension; IV-Leg-5 133 (125); IV-Leg-6 165 (185–188); III-Leg-3 and 4 with long, stiff swimming setae; the IV-Leg-4 distal process bears four thick, somewhat wavy swimming setae; IV-Leg-3 and 5 bear long stiff, swimming setae; dorsal surface of IV-Leg-5 bears three short, spine-like setae placed in a straight line.

FEMALE: Idiosoma 788–809 long, 651–662 wide; both anterior and posterior margins rounded (Fig. 4 G). Dorsal shield 663–683 long and 515–536 wide, bearing the postocularia and three pairs of glandularia (Fig. 31). Acetabular plate region 420–425 wide; acetabular plates laterally directed, short, bowed and narrow in relation to gonopore length; gonopore 189 long and 179 wide; one and a half rows of idiosoma pores between second and third coxae, three rows between left and right posterior coxae (Fig. 4 H, 32). Dorsal lengths of palpal segments: P-I 29–30; P-II 68–71; P-III 41–43; P-IV 69–70; P-V 30–34. Palp structure and chaetotaxy as in the male. Dorsal lengths of distal segments of first leg: I-Leg-4 (91–95); I-Leg-5 (88–94); I-Leg-6 (115–125). Dorsal lengths of distal segments of fourth leg: IV-Leg-4 (140–150); IV-Leg-5 (163–168); IV-Leg-6 (175–195); IV-Leg-3 and 4 bear considerably long, stiff swimming setae; IV-Leg-5 and 6 bear numerous short swimming setae; dorsal surface of IV-Leg-5 bears three short, spine-like setae placed in a line.

Etymology. The name refers to the urban conditions surrounding the Xochimilco natural reserve, where the specimens were collected.

Discussion. The P-II chaetotaxy of Arrenurus urbanus sp. nov. is complicated, as it consists of a mixture of two types of setae, i.e., many long needle-shaped setae and four snake-shaped setae. Arrenurus spathulifer Lundblad from Argentina, Brazil, Paraguay and Uruguay (Lundblad, 1944) presents very similar palp chaetotaxy and idiosoma shape to A. urbanus, except that in A. spathulifer the cauda is not constricted at its base. Arrenurus willinki Rosso de Ferradás 2000 from Argentina and Uruguay, and Arrenurus brevicaudatus Viets 1936 known from Argentina, Bolivia, Brazil, Colombia, Guyana, Peru, Uruguay and Venezuela, also exhibit a mixture of two types of setae in the palp, but considerably fewer than A. urbanus; in those species, the dorsoglandularia position and the general shape of idiosoma are also similar to A. urbanus, but the proportions of the cauda are different among the three species.