The diagnosis of Myrmozercon used here is based on that of Shaw and Seeman (2009). Most species of Myrmozercon, including the type species Myrmozercon brevipes, show moderate to strong hypertrichy on the dorsal shield. However, Myrmozercon burwelli Shaw & Seeman, 2009 (24-25 pairs), and the new species, have a reduced dorsal chaetotaxy. All species appear to have asymmetrical and unpaired setae on the dorsal shield, which makes it difficult to recognise their homology except the new species. In most species the dorsal shield is reduced or truncated posteriorly to expose a strip of unsclerotised opisthonotal skin, but this is not true for every species. Species of Myrmozercon also vary in the presence or absence of metasternal setae st4, the sternal shield of new species is extended to which the sternal shield is fused with the endopodal plates, with three pairs of setae and three pairs of lyrifissures and metasternal setae (st4) absent. The leg chaetotaxy of Myrmozercon species is variable, and does not provide diagnostic characters that define the genus (Shaw and Seeman 2009) and this is very characteristic and fixed in the new species. The new species has one ventral seta on the palp trochanter the same as in most species of Myrmozercon. Shaw and Seeman (2009) described a swelling on the dorso-distal edge of the palp trochanter in several species, but this structure is not present in new species. This instability in morphology, and the edentate chelicerae and short peritremes of Myrmozercon, suggest that Myrmozercon is parasitic on its ant hosts, and not simply a commensal in its host’s nests, but this has not been established experimentally. The specimens of new specieswere found clinging to the abdomen and head of the ants.

Holotype, female, Kenevist Rural District in the Central District of Mashhad County, Khorasan Razavi Province, Iran, 36.97'N, 59.68'E, alt. 945 m, 25 April 2012, A. Ghafarian coll., in nest of Monomorium sp. (in YIAU). Paratypes, four females, same data as holotype (in JAZM and ANIC).

Figures 1–13. Dorsal idiosoma (Fig. 1). Length 522–534. Dorsal shield length 488–500, width 420–436 (n = 5). Shield posteriorly truncate, not covering entire idiosoma, leaving a curved strip of unprotected skin posterior to setae J5, shield without distinct reticulate ornamentation over whole surface; with 33 pairs of setae, 21 podonotal (z2 absent), 12 opisthonotal (Z4, S5 absent) and Z5 in soft skin posterior to shield, almost all setae except j1 and J4 slightly barbed in apical third or less, with club-like tip (Fig. 2), opisthonotal setae very long, reaching well past base of next posterior setae, dorsal shield setae increasing in length from anterior to posterior (j1 25-27, J1 54-59, J2 67-69, J3 79-82), without unpaired and asymmetrical seta, setae on shield uniform in length and thickness except j1 (25-27) and J4 (20-25) very fine and minute. A pair of very fine and minute setae in R series on the lateral soft skin but appear on ventral view. Shield with eight pairs of minute pores and lyrifissures including a pair of lyrifissures situated near z1, other pores inconspicuous.

Ventral idiosoma (Fig. 3). Tritosternum with short broad base (10-11 × 15-17 wide) fused to sternal shield, bifurcated at a short distance above suture, laciniae 37-40 in length, with smooth edges, strap-like and broad at base; pre-sternal shields fused with sternal shield. Sternal shield (length 248-255) narrowest between coxae II (104-108) widest between coxae II and III (218-22), with biconvex anterior margin and extending beyond level of st1, lateral margins thickened and posterolateral corners fused with endopodal shield; posterior margin concave; shield bearing three pairs of smooth pointed setae (st1 30-37, st2 40-45, st3 50-51) and two pairs of lyrifissures, one pair between setae st1 and st2 and the other between st2 and st3; surface with indistinct reticulate ornamentation. Seta st4 absent, metasternal pores also on extent of sternal shield but metasternal plates apparently absent. Genito-ventral shield wide, strongly tapering posteriorly, 320–346 long, 168–174 maximum width. Surface of shield smooth with longitudinal markings in anterior half; with one pair of simple setae st5 (35–37). Anal shield triangular, its anterior without lineate ornamentation, cribrum small, anal pores indistinct, bearing short post-anal seta 15-17 long, and a pair of para-anal setae 37–42 long. Opisthogastric skin with long, narrow metapodal plates (40–44 × 8–10 wide) and eight pairs of setae, almost all setae slightly barbed in apical third or less, each arising on small sclerotised platelet (Figs. 4, 5), (Jv1 47-50, Jv2 35-37, Jv5 64-73, Zv1 37-42, Zv2 45-50, Zv3 55-63, Zv4 45-50, Zv5 67-75). Peritreme very short (35-40), extending to posterior level of coxae Ш. Peritrematal shields absent, post-stigmatal section conspicuous, with one pair of pore.

Gnathosoma. Hypostomal groove with nine rows of denticles, 10 to 15 very fine denticles per row (Fig. 6). Hypostome with three pairs of setae, internal posterior hypostomal setae h3 longest, palp coxal setae absent; surface of hypostome ornamented with transverse and curved lines. Palp chaetotaxy: trochanter 1, femur 5, genu 5, tibia 12; all palp setae pointed, palp tarsal claw two-tined, dorsodistal edge of palp femur without swelling. Epistome triangular, smooth, with pointed apex (Fig. 7). Chelicera hyaline, fixed digit of chelicera reduced, with four minute terminal denticles, pilus dentilis, dorsal lyrifissure present (Fig. 8); movable digit weakly sclerotised, distally curved, with one small subterminal tooth and one stronger terminal tooth, cheliceral seta absent, arthrodial corona with hyaline flap without filaments (Fig. 8). Corniculi long, weakly sclerotised.

Legs: Legs II and III short (258–268, 268–272), I and IV longer (288-298). Chaetotaxy: Leg I: coxa 0 0/1 0/1 0, trochanter 1 0/1 1/1 1 (pd thick), femur 1 2/1 2/1 1 (ad1 and pd1 long, ventral setae all thick, Fig. 9), genu 1 2/1 2/1 1 (ad1 and pd1 long with club-like tip, ventral setae all thick, Fig. 9), tibia 1 2/1 2/1 1 (ad1 and pd1 long with club-like tip, ventral setae all thick, Fig. 9). Leg II: coxa 0 0/1 0/1 0, trochanter 1 0/1 0/2 1, femur 1 2/1 2/1 1 (ad1 and pd1 thick, al and pl long, Fig. 10), genu 1 2/1 2/1 1 (ad1 thick, pd1 long with club-like tip, al and pl long, Fig. 10), tibia 1 1/1 2/1 1 (al and pl long, Fig. 10). Leg III: coxa 0 0/1 0/1 0, trochanter 1 0/1 0/1 1 (al thick), femur 1 2/1 1/1 1 (ad1 thick, al and pl long, Fig. 11), genu 1 2/1 2/1 1 (ad1 and pd1 thick, ad1 in two paratypes club-like tip, al and pl long, Fig. 11), tibia 1 1/1 2/1 1 (al and pl long, Fig. 11). Leg IV: coxa 0 0/1 0/0 0, trochanter 1 1/2 0/1 0 (ad thick), femur 1 2/1 1/1 0 (al long Fig. 12), genu 1 2/1 2/1 1 (ad1 and pd1 thick, ad1 in two paratypes club-like tip, al and pl long, Fig. 12), tibia 1 1/1 2/1 1 (al and pl long, Fig. 12). Tarsi I-IV with 16 setae, pre-tarsi with membranous ambulacrum, claws absent.

Genital structures: Insemination ducts opening on posterior margin of coxa III; sacculus an irregular, dark coloured mass behind coxae IV, ducts entering sacculus via a pair of circularopenings (Fig. 13).

The species is named in memory of Cyrus the Great (Old Persian: Kuruš; c. 600 BC or 576 BC–530 BC) was the first Achaemenian Emperor of Persia, as the “father of the Iranian nation”, who issued a decree on his aims and policies, later hailed as his charter of the rights of nations.

Myrmozercon cyrusi differs from all other species in the genus by its very short peritreme, palp coxal setae absent, genua I-IV with similar chaetotaxy (1 2/1 2/1 1) and trochanter of palp with only one ventral seta.