Thiratoscirtus elgonensis

Thiratoscirtus elgonensis  is a species of jumping spider in the genus Thiratoscirtus that lives in Nigeria. It has only been found on Mount Elgon, after which it named. The species was first described in 2016 by Angelika Dawidowicz and Wanda Wesołowska. It is a medium-sized spider, with a cephalothorax that is between 1.8 and 2.7 mm long and an abdomen that is between 2.0 and 2.8 mm in length, both oval in shape. It is generally brown with a central lighter streak running down both the carapace, the hard upper part of the cephalothorax, and the top of the abdomen until it ends in a series of chevrons. The area around its eyes is black and Its face, or clypeus, is light brown. The male has pedipalps that are similar to the related Thiratoscirtus efik' but differs in details, including the size of the spike on the palpal tibia known as the tibial apophysis. The female has a distinctive epigyne with a heart-shaped depression and wide insemination ducts.

Taxonomy
Thiratoscirtus elgonensis  is a species of jumping spider that was first described by Angelika Dawidowicz and Wanda Wesołowska in 2016. One of over 500 different species identified by Wesołowska in her career, it is named for the Mount Elgon, where it was first found. They allocated the spider to the genus Thiratoscirtus, first circumscribed in 1909 by Eugène Simon. The genus is very diverse and contains many monophyletic groups.

Thiratoscirtus is a member of the subtribe Thiratoscirtina in the tribe Aelurillini. The genus is closely related to Nimbarus. Wayne Maddison allocated the tribe to the subclade Simonida in the clade Saltafresia in the clade Salticoida. In 2016, Mellissa Bodner and Maddison proposed a subfamily Thiratoscirtinae for the genus and its related genera. This overlapped with a group of genera named Thiratoscirtines after the genus, created by Jerzy Prószyński in 2017. Phylogenetic analysis has shown that the genus is related to the genera Alfenus, Bacelarella, Longarenus and Malloneta. It is likely to have diverged between 16.3 and 18.7 million years ago.

Description
Thiratoscirtus elgonensis  is a medium-sized spider. The spider's body is divided into two main parts:a cephalothorax and an abdomen. The male has a cephalothorax that measures typically between 2.0 and 2.5 mm in length and 1.6 and 1.9 mm in width. The carapace, the hard upper part of the cephalothorax, is a moderately high oval that is generally brown and covered in brown hair. It is marked with a light band across the middle and white streaks formed by hairs on the sides. There is a furrow-like depression in the centre of carapace. A black field surrounds the eyes that is covered in black hairs, with a few longer brown bristles visible particularly around the forward eyes. The sternum, the underside of the cephalothorax, is brown. Its face, or clypeus, is low and light brown with light hairs. Its mouthparts are brown, with paler tips on the labium and maxillae while chelicerae are marked by having a single tooth at the back.

The spider's abdomen is a small oval that measures between 2.1 and 2.7 mm long and between 1.4 and 1.8 mm wide. It is a generally brown oval with a pattern of yellowish chevrons towards the rear. The chevrons are covered in yellowish hairs, the remainder of the abdomen with brown hairs. The sides are whitish and the underside yellowish and marked with brown markings. The spider's spinnerets are light brown, as are its legs. The legs have long thin brown hairs and a single spine.

The pedipalps, sensory organs near the mouth, are small and covered in long dense hairs. The male copulatory organs include a rounded hairy cymbium that surrounds the smaller bean-like palpal bulb. A relatively long embolus extends from the middle of the bulb and curves around towards th top of the cymbium but finishes in a point before it reaches that point. Its palpal tibia is small and has a small single slightly curved spike, or tibial apophysis, extending from one side and a clump of long hairs on the other. The pedipalp is very similar to the related Thiratoscirtus efik, but the embolus is longer and the tibial apophysis is larger.

The female is similar to the male in size with a cephalothorax that is measures typically between 1.8 and 2.7 mm in length and a similar range of widths. The carapace is generally lighter but has a similar pattern, with a lighter streak running down the middle. Between {2.0 and 2.5 mm long and 1.5 mm and 2.0 wide, is abdomen is brown with a single light irregularly-shaped streak running down the middle, finishing in a pattern of chevrons towards the rear. The legs are a similar brown to the majority of the body.

The female's copulatory organs are distinctive with an epigyne that is particularly unusual and helps distinguish the species from others in the genus. It has a depression in the middle that is heart-shaped and two extremely wide insemination ducts. There is also a single spine evident on the palpal tarsus. The openings are fissured and the insemination ducts lead to spermathecae, or receptacles, that have strong sclerotization, each with two chambers. The first chamber is curved and the second spherical.

Distribution and habitat
Thiratoscirtus spiders generally live in Africa and are particularly common in the forests of Central and West Africa. Thiratoscirtus elgonensis  is endemic to Nigeria. It has only been found at Mount Elgon. The fact that the species has only been found there, along with a number of other spiders including Belippo elgonensis, led to Dawidowicz and Wesołowska speculating that the mountain acts as a "centre of endemism".

The spider thrives in high altitudes. The holotype was at an altitude of 2000 m above sea level, while others have been found as high as 3580 m. It is generally found living in vegetation. Some spiders live in moss underneath trees of genera like Alchemilla and Erica. Others live amongst bushes like Acanthus amongst forests of bamboo. One example was found on the giant groundsel Dendrosenecio johnstonii.