Description of four new species of armoured spiders (Araneae, Tetrablemmidae) from Sumatra, Indonesia

Abstract Four new species of armoured spiders from Sumatra, Indonesia are described. Three species are described in the genus Ablemma Roewer, 1963 and one species in the genus Brignoliella Shear, 1978; Ablemmaandrianasp. n. (male), Ablemmacontritasp. n. (male and female), Ablemmakelincisp. n. (male) and Brignoliellapatmaesp. n. (male and female). The female of Ablemmasingalang Lehtinen, 1981 is described here for the first time. The first record of Brignoliella for Sumatra is also presented.


Introduction
Tetrablemmidae are small (0.8-2 mm), cryptozoic spiders predominantly living in forest leaf litter (Jocqué and Dippenaar-Schoeman 2007); they are very diverse in Southeast Asia. Of the 131 known species in this family, 50 have been described from this region (World Spider Catalog 2018). Thirty-five species are found in Eastern and Southern Asia with the remaining species distributed around the world except in Central and Western Asia, Europe, Central America, in the Arctic and Antarctic region. The south Asian fauna of the families Tetrablemmidae and Pacullidae was first studied by Shear (1978) followed by Deeleman-Reinhold (1980) and finally in 1981, Lehtinen published a world revision that united the two families into the family Tetrablemmidae. More recently, taxonomic work has been done on the Asian fauna by Lin et al. (2012Lin et al. ( , 2017Lin et al. ( , 2018. The family was recently redefined to include only 27 genera that belong to the sub-family Tetrablemminae, and the sub-family Pacullinae was elevated to family level including four genera (Wheeler et al. 2017).
In Sumatra, Indonesia, the family Tetrablemmidae remains poorly documented; a total of six species in four genera have been recorded on this island (Stenchly 2011, World Spider Catalog 2018: Ablemma baso Roewer, 1963, A. erna Lehtinen, 1981, A. singalang Lehtinen, 1981; Pahanga lilisari Lehtinen, 1981; Singalangia sternalis Lehtinen, 1981; and Tetrablemma mardionoi Lehtinen, 1981. In this paper, we describe four new species of Tetrablemmidae and present the first record of the genus Brignoliella from Harapan and Bukit Duabelas, Jambi Province, Sumatra. The specimens were sampled from leaf litter and topsoil in lowland rainforest of Sumatra and were collected as part of the Ecological and Socio-economic Functions of Tropical Lowland Rainforest Transformation Systems project (EFForTS), which investigates consequences of converting lowland rainforest into plantation systems (Drescher et al. 2016). Extensive field surveys are being carried out in rainforest, jungle rubber agroforests, rubber plantations and oil palm plantations and the spider fauna is currently being studied in each habitat for its taxonomic and ecological composition. This is the second paper describing new species of spiders from this project, following the recent description of new species of goblin spiders (Fardiansah et al. 2018).

Material and methods
All specimens were collected in the framework of the EFForTS project (Drescher et al. 2016). The material was collected on the plots of the Collaborative German--Indonesian Research Center (CRC990) with the following ecosystem types: primary degraded lowland rainforest, jungle rubber originating from planting rubber trees (Hevea brasiliensis Müll.Arg.) into lowland rainforest but predominantly composed of rubber trees, rubber monoculture, and oil palm (Elaeis guineensis Jacq.) monoculture. Spiders were collected with two methods: (1) by sieving litter layer from the area of 1 × 1 m and further hand collection and (2) by taking 16 ×16 cm samples of litter and the underlying top 5 cm of soil and further heat extraction; all collected specimens were placed into 70% ethanol (Barnes et al. 2014, Klarner et al. 2017. The material examined is deposited in the following institutions: Indonesian Institute of Sciences Cibinong, Indonesia (LIPI); Zoological Museum Hamburg, Hamburg, Germany (ZMH).
Specimens were examined in 75% ethanol under a Leica M125 dissection microscope. Specimens were photographed with a custom-made BK Plus Lab System by Dun, Inc. with integrated Canon camera, macro lenses (65 mm and 100 mm) and the Zerene stacking software. Female genitalia were excised using a sharp entomological needle placed on a slide in lactic acid and observed under a Leica microscope DM2500 LED compound microscope. A Leica DMC 4500 digital camera attached to the microscope was used to photograph all the structures to be illustrated. The digital photos were used to trace proportions and the illustrations were detailed and shaded by referring back to the structure under the microscope. All morphological measurements are given in millimetres. Matching of males and females can be challenging and when in doubt females were not matched. Otherwise males and females were matched based on the following criteria: (1) collected in the same sample, (2) body size and colour, and (3) abundance. Morphological nomenclature follows Lin et al. (2017Lin et al. ( , 2018 Roewer, 1963 Diagnosis. The genus Ablemma most resembles the genera Singaporemma Shear, 1978 andSulaimania Lehtinen, 1981 but it can be distinguished from both genera by the combination of the following characters: 6, 4 or 2 eyes; sternum reticulate ( Fig. 2); male carapace without clypeal horn (Figs 3,4), chelicerae with acute cheliceral apophysis at base of fang (Figs 47-49); heavy right-angled embolus (Figs 7,14,27); female with small posterolateral corner of preanal scutum (Fig. 19).
Compostion. Twenty-five species were known before the present publication, eight of which are only known from one sex (World Spider Catalog 2018).

Ablemma andriana
Female. Unknown. Natural history. Most specimens were collected in secondary lowland rainforest; one specimen was collected in a rubber plantation.
Etymology. The specific name is a noun in apposition taken from Latin, meaning broken, in reference to the tip of the embolus.
Diagnosis. Males can be distinguished from all congeners with the exception of similar species (A. unicornis Burger, 2008, A. erna, A. kaindi Lehtinen, 1981, and A. malacca by the blunt apical end of the male embolus (Figs 12, 13). Furthermore, A. contrita sp. n. differ from A. unicornis by the lack of an anterior tooth on the carapace behind the eye group (Figs 8,11) vs. present in A. unicornis (see Burger 2008, 254, figs 1, 2); from A. erna and A. kaindi (see Lehtinen 1981, 128-129, figs 166, 171) by its shorter and flatter embolus, and the more elongated palpal bulb (Figs 12, 13); from A. malacca by the concave and swollen pars cephalica (Fig.11), straight and not swollen in the latter (see Lin et al. 2017, fig. 7). Females are distinguished from similar species as follows: from A. unicornis by the absence of the posterior pit on the sternum in females (Fig. 16); from A. kaindi by their longer inner genitalic plate; from A. erna by their wider, not expanded apically inner gentitalic plate; from A. malacca by the shorter and thicker inner gentitalic plate (Fig. 20).
Natural history. Specimens were only collected in lowland rainforest with rubber trees.
Distribution. Known only from the type locality, Harapan, Sumatra. Etymology. The specific name is a noun in apposition taken from Indonesian official language «bahasa», meaning rabbit, in reference to the eye projection that resembles rabbit ears.
Female. Unknown. Natural history. So far, specimens were collected only from secondary lowland rainforest and never from modified forests such as rubber or oil palm plantations.
Distribution. Known only from the type locality, Bukit Duabelas, Sumatra.

Ablemma singalang Lehtinen, 1981 Figs 28-33
Type material. Holotype ♂ and paratype ♂ from Indonesia, Sumatera Barat, Padangpanjang district, Gunung Singgalang (1750 m Diagnosis. Females of Ablemma singalang can be distinguished from most congeners by the small rounded basal boss on the chelicerae (Fig. 30, arrow), and the elongated narrow inner plate of the internal genitalia (Fig. 33); short and triangular in other species. Furthermore, females are distinguished from A. malacca with similar internal genitalia, by the larger carapace tubercles (Fig. 31), smaller in the latter species (see Lin et al. 2017, fig. 7H).
Natural history. Male and females specimens were collected together in secondary lowland rainforest, rainforest with rubber trees, and rubber plantation.
Composition. Twenty-three species were known before the current publication of which eight are known from one sex only (World Spider Catalog, 2018).