Sumatrella chelonica gen. n., sp. n., a new remarkable genus and species from Indonesia, Sumatra (Acari, Uropodina, Oplitidae)

Abstract A new genus Sumatrella gen. n. is described and illustrated based on the new species Sumatrella chelonica sp. n. collected in Sumatra, Indonesia. The new genus belongs to the family Oplitidae based on its hypertrichous internal malae and the absence of strongly sclerotized structures on the dorsal shield. The new genus is closely related to the genus Chelonuropoda Sellnick, 1954 but the transverse furrow on ventral idiosoma close to coxae IV and the strongly sclerotized C-shaped dorsal line are missing in the new genus. These characters can be found in species of Chelonuropoda.


Introduction
The Uropodina mites are one of the well-characterized members of the soil mite fauna. They can be found with a high diversity in tropical regions (Lindquist et al. 2009), but currently only 10% of the known species are from this region (Vázquez and Klompen 2007).
The family Oplitidae (Lindquist et al. 2009, Beaulieu et al. 2011) is a very district group among the Uropodina, which possesses several specific characters. The internal malae is subdivided into several branches bearing pilose margins, the hypostomal setae are not situated in a longitudinal row, and the dorsal shield does not bear strongly sclerotized structures. Its members can often be found in ant nests (Mašán 2001). This family was previously treated as one genus, and divided into several species groups in previous systems (Wiśniewski and Hirschmann 1993). Recently it was elevated to family level [Lindquist et al. (2009), Beaulieu et al. (2011] and is divided into further genera (e.g. Kontschán 2010, Kontschán andStarý 2012).
In 2014, some days were spent in the Arachnida collection of Natural History Museum in Geneva, where I found several specimens of a very unusual oplitid species, described here as a new genus and new species.

Material and methods
Specimens of this unusual species were cleared in lactic acid, investigated on halfcovered deep slides and illustrations were made with the aid of a drawing tube. Photographs were taken with a Nikon CoolPix900 digital camera. All specimens are stored in ethanol and deposited in the Natural History Museum in Geneva (NHMG). All measurements are given in micrometres (μm).

Taxonomic
Sumatrella gen. n. http://zoobank.org/360C7C81-9BA6-4CEC-B92A-9F02B5E06768 Diagnosis. 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.
Type species. Sumatrella chelonica sp. n. Etymology. The name of the new genus refers to the name of island where the specimens were collected. Gender feminine.
Systematic notes. 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 (Figs 18-19). Color reddish brown.
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. Etymology. The name of the new species refers to the raised shape of the mite body which is reminiscent of a turtle.

Zoogeographical notes
Species of the probably closely related genus Chelonuropoda Sellnick, 1954 occur in South America and the Afrotropical region; a distribution pattern which has been named 'Amphiatlantic' (Kontschán and Starý 2012). Based on zoogeography, the genus Chelonuropoda must have originated during a geological period when Africa and South America were still connected to each other; i.e. prior to the Upper Cretaceous. The new genus occurring on Sumatra Island is not situated on a Gondwanan fragment. Therefore we can consider two hypotheses about its distribution: either Sumatra was colonized by the new genus by other dispersal means, or the similarities in morphology are the result of parallel evolution and are examples of homoplasy.