Description of two new species of Xevioso (Araneae: Phyxelididae) from Southern Africa, with the northernmost localities for the genus

Abstract. Two new species of Phyxelididae are described from southern Africa: Xevioso cepfi sp. nov. (♂♀), from mountains in the Niassa Province of northern Mozambique, and X. megcummingae sp. nov. (♂♀), from urban Harare, northern Zimbabwe and the Viphya Mts in Malawi. They represent the northernmost localities of the genus. An identification key, partially adapted for the new species, is presented. The biogeographical importance of the mountain areas on both sides of the northern part of Lake Malawi is discussed.


Introduction
Phyxelididae is a fairly small spider family with 14 genera and only 64 species. It has a peculiar distribution, mainly in southern and eastern Africa and Madagascar, with a few outliers in Turkey and Indonesia. It retained subfamily status in the complete revision by Griswold (1990) but received family status in the study of Griswold et al. (2005).
Xevioso was so far restricted to Southern Africa, with one species extending its area into Zimbabwe (X. orthomeles Griswold, 1990) and one (X. jocquei Griswold, 1990) widely separated from the rest in Malawi.
During a BINCO-expedition (see BINCO.eu) in November 2016 to the remote mountains of Chitagal, Sanga and the Njesi Plateau (Niassa Province) in northern Mozambique (Jones et al. 2017), an undescribed species of Xevioso was found. Further evaluation of the Phyxelididae collection in the Royal Museum for Central Africa (RMCA) uncovered a male and female of a second remarkable species from Zimbabwe, with one more specimen from the Viphya Mts in Malawi.
Knowledge on the distribution of the genus is greatly expanded here with the addition of two new species: one in northern Mozambique and another with a remarkable distribution, in northern Zimbabwe and a remote locality in Malawi. Herein, we describe and illustrate these new species and thus provide the northernmost localities for the genus.

Material and methods
The specimens examined in the current study were preserved in 70% ethanol and examined using a Nikon SMZ800 stereo microscope for measurements and descriptions. Male palps and female genitalia were drawn with a WILD M10 stereo microscope (Leica). Female epigynes were detached from the abdomen, temporarily mounted in a clearing mixture of methyl salicylate and cedukol (Merck, Darmstadt) and observed with a Leitz Dialux 22 microscope and subject to automontage with the Syncroscopy software. Male palps and habitus were photographed with a Leica MZ16 using the Leica Application Suite (LAS) automontage software (ver. 3.8; Leica, https://leicacamera.com), with a Z-stack of 15-25 images merged into a single photomontage. For SEM photos, specimens were dried overnight in hexamethyldisilazane, gold coated, and examined and photographed with a JEOL 6480 LV scanning electron microscope. Maps were created with the online tool SimpleMappr (Shorthouse 2010 Fig. 1A-B). Carapace light yellowish-brown, lighter posteriorly, shading to dark brownishorange at pars cephalica, blackened around eyes and between AME. Co and Tr concolorous with posterior region of carapace, remainder of legs darkened to pale brownish-orange at tip of each metatarsus. Chelicerae darkest part of body, dark red-brown, with clypeus orange-brown. Sternum cream yellow. Dorsum of abdomen grey, venter pale grey, with some paler areas, pedicel concolorous with sternum.
CARAPACE. Margins weakly sinuate, with very sparse short setae. Carapace with highest point in cephalic area, 1.5 times higher than at fovea (1.63 vs 1.04).
ABDOMEN. With short black setae, denser laterally and longest at posterior apex. Venter with dispersed setae, longest at posterior apex.
LEGS. Formula 1423, F I thicker, weakly undulated. P with small but distinct retrolateral process/ protrusion. Mt I with very weak pl concavity ⅔ towards apex (fi g. 4D).
LEG MEASUREMENTS.  . F with two short stout anterobasal thorns. T with strong, dark axle-shaped process and pronounced DP, delimiting concavity with narrow opening. Palpal bulb simple, not divided into basal and retrobasal lobes. Embolus broadest at base but tapered apically into slender corkscrew, with three coils. TA3 with two acutely pointed prongs, TA2 lobate with short, blunt tip. EBS tri-partite, EBA1 sub-quadrate with weak posterior point, EBA2 recurved and slender, EBA3 fi ne and serrated with apex curving dorsally. Conductor with rl transverse ridge, basocentral lobe distad of embolus, and lateral and apical fringe.  COLOUR. Carapace uniform, creamy yellow-brown. Clypeus from AME's darker, orange-brown, thin line around margin of clypeus black. Chelicerae substantially darker, a deep reddish brown. Legs concolorous with carapace, except leg I: darkening at Mt a deep orange. Abdomen grey with short black setae, venter paler grey, creamy at anterior margin with pedicel concolorous with carapace base.
CARAPACE. Margins very weakly sinuate, if at all. Sparse black setae reach highest abundance medially, anterior of the fovea.
LEGS. Formula 143? (missing leg II). F I undulates weakly ⅔ of length toward apex. As in males, distinct but small rl process/ protrusion at pa. Females lack pl concavity at the mt present in males. (2) palpal T with dorsal hyaline process thin, slightly curved, appearing nail-like in rl view; (3) palpal DP broad and sub-triangular; (4) TA3 tegular processes short and blunt; TA1 absent. Females are recognized by the CO far apart and the longitudinal axis of the spermathecae diverging anteriad.

Etymology
The species name is a matronym in honour of Zimbabwean naturalist, Meg Cumming, collector of the type material.  (Fig. 6A). Carapace light yellowish-orange, darkened anteriorly at pars cephalica, chelicerae deep reddish-brown, darkest part of the body; black pigment around eyes, PME without black pigment, AME's joined by dark pigment. Sternum light yellow, margins darkened to deep reddish-brown. Co and Tr I brownish-orange, darker than others, cream yellow. F I orange, to brownish-orange up to Mt; other legs light brownish-yellow to orange at Mt. Abdomen and venter cream to white entirely.
CARAPACE. Margin weakly sinuate. Short black setae dispersed in irregular and sparse patches. Fovea deeply concave, carapace fl at throughout, clypeus height 1.1 × height of carapace at fovea.
ABDOMEN. Dorsum with very few setae anteriorly, denser on posterior part. Venter with minimal short fi ne setae. PALP. With dense procurved setae and toothless claw.

Discussion
It is well known that the mountain fauna and fl ora of the South African mountains ranging from the Western Cape in the south-west to the Limpopo Province in the north, are unique and have a high proportion of endemic species (Axelrod & Raven 1978). The Limpopo appears to be a natural boundary for most of the southern organisms absent in tropical Africa. However, there are a number of elements that are typical of the Cape fauna occurring north of the Limpopo on inselbergs in Malawi and Mozambique, reaching their northernmost limit there. The geological background of this phenomenon is explained in Axelrod & Raven (1978) and Delvaux (2001). The cedars of the genus Widdringtonia Endl. are an outstanding botanical example, as they reach their northernmost distribution on Mt Mulanje (Malawi) (Pauw & Lindner 1997), a well-known large inselberg with an altitude of about 3000 m. It harbours numerous representatives of taxa with a southern African distribution (Strugnell 2002). Among these is Sphaerotherium transzambeziacum Jocqué, 1984, a pill millipede belonging to a family that otherwise occurs only south of the Zambezi River (Jocqué 1984). Two more inselbergs at about the same latitude just across the border in Mozambique are Mt Namuli and Mt Mabu, which have been inventoried for invertebrates, but only superfi cially (Timberlake et al. 2009(Timberlake et al. , 2012. It has been questioned whether these inselbergs are the northernmost high-altitude leftovers of a fauna that had a strong connection with the Cape fauna (Jocqué 1983(Jocqué , 1984. The case of Xevioso, which clearly has its center of distribution in eastern South Africa, is interesting in this context. The species X. jocquei was considered as an anomaly as far as its distribution is concerned, but it could be explained as a high altitude remnant of a once larger area. It now appears that two more species are found much further north in mountain areas in northern Mozambique and Malawi, on both sides of Lake Malawi, and that the genus has a much larger distribution (Fig. 8). Xevioso cepfi sp. nov. has been collected on all plateaus of the Mozambique Niassa Region at altitudes between 1600 and 1800 m a.s.l. A fi rst hint of the geographic importance of these highlands was already suggested by the inventory of mammals Henrard 2018). The fi nd of X. megcummingae sp. nov. at quite a distance from the type locality, shows that the Viphya Mts in Central Malawi may also harbour more interesting endemics.
Our study confi rms the importance of these remote altitudinal ranges for the understanding of distribution patterns of southern African taxa with a predilection for montane habitats.