Idiosoma small, oval, posterior margin rounded and very convex. All part of marginal shield wide and fused anteriorly to dorsal shield. Dorsal and ventral setae smooth and needle-like. Genital shield of female octagonal, without sculptural pattern and anterior process. Dorsal and marginal shields neotrichous. Corniculi horn-like, internal malae with several long branches. Hypostomal setae h3 longer than others, h2 situated outside the longitudinal row h1–h4 and shorter than others. Tritosternum with narrow basis, laciniae divided into two short and two long pilose branches. Epistome hemispherical and marginally pilose. Leg I without claw, trochanters II-IV with a triangular process.

Sumatrella chelonica sp. n.

The name of the new genus refers to the name of island where the specimens were collected. Gender feminine.

On the basis of the shape of internal malae (divided into pilose branches), the absence of the T-shaped dorsal setae and the hypostomal setae h2 position lateral to row h1–h4, I refer this genus to Oplitidae. Recently several genera and species groups have been recognized in this family (Kontschán 2010, Kontschán and Starý 2012, Wiśniewski and Hirschmann 1993), but the new genus differs from the others on the basis of the very convex idiosoma, the octagonal genital shield and the wide marginal shield. Only the genus Chelonuropoda Sellnick, 1954 shares this combination of character states with the new genus (i.e. very convex idiosoma and wide marginal shield) but the former differs in several characters, the most important of which are summarized in Table 1.

Holotype. Female. Indonesia, Sumatra, West Sumatra Province, primary forest at buttom of Haran Canyon, near Echo Point, N of Pavakumbah, 0°06'21"S, 100°39'50"E, 500m, 8.VI.2006. leg. A. Schulz. Paratypes. Three females from Indonesia, Sumatra, West Sumatra Province, primary forest at buttom of Haran Canyon, near Echo Point, N of Pavakumbah, 0°06'21"S, 100°39'50"E, 500m, 8.VI.2006. leg. A. Schulz and 7 females from Indonesia, Sumatra, West Sumatra Province, distributed primary forest near road Lubuksikaping Bonjol, ca. 10 km S of Lubuksikaping, 0°03'16"N, 100°12'33"E, 500m, 12.VI.2006. leg. A. Schulz.

As for the genus.

Length of idiosoma 560–580 µm, width 470–510 µm, height 560–570 µm (n=11). Shape oval, posterior margin rounded and dorsally extremely domed (Figs 18–19). Color reddish brown.

Dorsal idiosoma (Figure 1): Dorsal and marginal shields fused apically. Dorsal shield neotrichous, all dorsal setae smooth and needle like (ca. 32–44 µm) (Figure 2). Surface of dorsal shield smooth, only some muscle scars can be seen at level of coxae IV. Marginal shield very wide (Figure 4) with darker and spine–like patterns on inner margins, setae on marginal shield similar in shape and length to dorsal setae (Fig. 4).

Ventral idiosoma (Figure 5): Tritosternum with narrow, quadrangular basis; laciniae with two short and two long pilose branches (Figure 9). Sternal shield without ornamentation, four pairs of sternal setae smooth, short (ca. 6–7 µm) and needle-like. St1 situated near anterior margin of sternal shield, St2 at level of anterior margin of genital shield, St3 at level of anterior margin of coxae III, St4 at level of posterior margin of coxae III. One pair of lyriform fissure situated close to anterior margin of sternal shield. Three pairs of longer (ca. 25–30 µm) and one pair of shorter (ca. 10–11 µm) ventral setae situated, all ventral setae smooth and needle-like. Two pairs of adanal setae short (ca. 5–6µm) smooth and needle-like, postanal seta smooth, needle-like and long (ca. 14–15 µm). Second setae from postanal seta associated with a setae-like sensory organ. Margins of ventral idiosoma bearing numerous smooth and needle-like setae (ca. 14–17 µm). Surface of ventral shield without ornamentation (Figure 6). Genital shield octagonal, ca. 180 µm long and ca. 130 µm wide, without sculptural pattern and anterior process. Stigmata situated between coxae II and III. Prestigmatic part of peritremes C-shaped with a very short central branch, poststigmatic part short and straight (Figure 8). Pedofossae deep, their surface smooth, separated furrows for tarsi IV absent.

Gnathosoma (Figure 9): Corniculi horn-like, internal malae longer than corniculi and divided into several pilose branches. All hypostomal setae smooth and needle-like, h1 (ca. 25–27 µm) situated near anterior margin of gnathosoma, h2 very short (ca. 9–10 µm) and situated close to h3 and placed lateral to h1-h4 row. Setae h3 long (ca. 33–35 µm), h4 shorter (ca. 16–17 µm). Three ventral denticles situated on central part of ventral gnathosoma at level of h4.

All setae on palp smooth and needle-like (Figure 12). Epistome hemispherical and marginally pilose (Figure 10), chelicerae with one teeth on movable and fixed digits, internal sclerotized node present (Figure 11). Scale bars in micrometers.

Legs (Figures 15–18): Claws absent at the tip of the ambulacral prolongation of leg I. Flap-like prolongations placed on femora II–IV and an unusual triangular process situated on trochantes II-IV.

Male, nymph and larva are unknown.

The name of the new species refers to the raised shape of the mite body which is reminiscent of a turtle.