(Figs. 63–67)

Material examined. Holotype male, pond “Katbakkies”, Skitterykloof N of Ceres, Western Cape Province, South Africa, 32° 52.984 S 19° 44.286 E, alt. 581 m a.s.l., 4-xi-2004 (BMSA). Paratypes: six males, 1 female (not sclerotized) (BMSA), seven males, one female (RMNH), same data as holotype.

Diagnosis. Petiole hyaline with a serrated posterior margin and more anteriorly a rectangular chitinized structure. The female can be identified by the large distance of the fourth coxal plates in combination with the rounded sclerotized patches of the gonopore connected by a medial strip of sclerotization and the shape of the genital plates.

Description. Male: Idiosoma brownish, 972 (940–1016) long and 757 (721–802) wide. Idiosoma anteriorly truncated, anterior margin straight. Cauda not set off from anterior idiosoma, posterior idiosoma with a large concavity. Posterior margin with a closed cleft, which is widened more anteriorly. Dorsal shield complete, 547 (526– 575) long and 502 (478–567) wide, somewhat pear-shaped (more distinct in some of the paratypes). Petiole tubelike, hyaline, with a serrated posterior lower margin and more anteriorly upper margin with a rectangular chitinized structure. Anterior coxal plates not reaching to anterior idiosoma margin. Medial distance of fourth coxal plates large. Medial margin of third coxal plates as large as medial margin of fourth coxal plates. Gonopore 64 long. Genital plates long and narrow, extending onto dorsum (but this only visible in young, not sclerotized males). Lengths of PI-PV: 42, 92, 60, 94, 50; PII with three setae near anterior margin of segment. Lengths of I-leg-4-6: 144, 156, 150. Lengths of IV-leg-4-6: 178, 130, 150; IV-leg-4 without a spur.

Female: Idiosoma reddish brown, 1094 long and 899 wide. Anterior idiosoma margin straight, idiosoma posteriorly truncated. Dorsal shield complete, 846 long and 608 wide. Anterior coxal plates reaching to anterior idiosoma margin. Medial margin of third coxal plates slightly longer than fourth medial margin of coxal plates. Medial distance of fourth coxal plates 1,4 times as wide as width of one genital valve. Gonopore 148 long and 166 wide. Genital valves with two rounded sclerotized patches connected by a strip of sclerotization. Genital plates short, a little bit than two times as long as wide. Lengths of PI-PV: 44, 80, 52, 118, 62; palp as in male. Lengths of I-leg-4- 6: 162, 148, 126. Lengths of IV-leg-4-6: 200, 182, 150.

Etymology. Named for the serrated posterior margin of the petiole.

Remarks. The serrated posterior lower margin of the petiole together with the rectangular chitinized structure will separate the new species from other species with a hyaline petiole. Like many other Micruracarus species, the relatively large female has a gonopore with rounded sclerotized patches, but in A. serratipetiolatus n. sp. these are connected by a wide strip of sclerotization.