Nothophantes, the horrid ground-weaver, is a critically endangered monotypic genus of European dwarf spiders containing the single species, Nothophantes horridus. It was first described by P. Merrett & R. A. Stevens in 1995, and has only been found in an area of Plymouth smaller than 1 square kilometre (0.39 sq mi). The genus name comes from the Ancient Greek νόθος (nothos), meaning "spurious", and hyphantes, meaning "weaver". The species name comes from the Latin horridus, meaning "bristly".
Taxonomy Nothophantes horridus is part of the Linyphiidae family and is closely related to two other genera: Lepthyphantes and Centromerus. The structure of the epigyne would suggest that Nothophantes belongs to the subfamily Lepthyphantinae. The form of the epigyne is very similar to that of the genus Centromerus and Centrophantes, however, the Chaetotaxy is very different comparing these genera and is more similar to the chaetotaxy of Troglohyphantes and Lepthyphantes. Nothophantes was considered to be included in the Lepthyphantes genus as it already was a large and diverse genus but the epigyne is too different to include it. The male was found after the female and it confirmed the status of the taxonomy. The male pedipalp structure supports the subfamily as Lepthyphantinae and is most related to some Lepthyphantes species. However, the elongated Fickert's gland in the radix is very similar to the Centromerus genus. The broad and heavily sclerotised paracymbium is closer related to most Lepthyphantes species.
Anatomy Nothophantes horridus has a total body length of 2.5 millimetres (0.098 in), and has only been found in three limestone quarries and one industrial site in the Cattedown area. Shapter's Field Quarry, the species' type locality, has since been developed by builders and is now the Plymouth Trade Park industrial estate. Its small size and habit of living deep inside cracks and crevices of rocks makes them difficult to find. The female horrid ground-weaver is diagnosable by its epigyne and chaetotaxy. The total body length ranges from 2.15 millimetres (0.085 in) to 2.95 millimetres (0.116 in), with a carapace length from 0.95 millimetres (0.037 in) to 1.25 millimetres (0.049 in) and 0.7 millimetres (0.028 in) to 0.9 millimetres (0.035 in) width. The abdomen is slightly bigger than the carapace with a length of 1.1 millimetres (0.043 in) to 1.6 millimetres (0.063 in). The sternum only has a length measuring from 0.55 millimetres (0.022 in) to 0.7 millimetres (0.028 in) and a width of 0.5 millimetres (0.020 in) to 0.65 millimetres (0.026 in). The colour of the female abdomen is pale grey or darker grey with pale yellow stripes on the dorsal side. The ventral side is also grey, sometimes with two pale longitudinal lines on the sides and a pale area anterior to the epigastric fold. The chaetotaxy is distinct in the Nothophantes horridus. The Carapace has short hairs in the region of the eye and on the clypeus, while the sternum is covered with long hairs interspersed with some shorter hairs. Lastly, the abdomen is covered with short hairs and scattered with long bristles on the dorsal side. There are multiple short hairs on the anterior face. All femurs have several ventral spines arranged in two rows and the patellae have one short proximal spine and one long distal spine. The eyes of the spider are moderately small, with the anterior median eyes spaced 0.5 diameters apart from each other and 2 diameters from the anterior lateral eyes. The posterior median eyes are positioned about 1.25 diameters from each other and 1.5 diameters from the posterior lateral eyes. The length of the legs of the horrid ground-weaver is the longest for the fourth legs with a total length of 4.28 millimetres (0.169 in), measured on a specimen with a carapace length of 0.96 millimetres (0.038 in). The second longest are the first legs (3.78 millimetres (0.149 in)), then the second legs (3.60 millimetres (0.142 in)), lastly, the third legs with a length of 3.38 millimetres (0.133 in). The epigyne is very distinctive from other species and is characterized by a large transverse atrium, that first curves anteriorly and then posteriorly. The vulva has prominent internal chitinised apodemes, which partially obscure the duct structure. Male horrid ground-weavers have a total body length of 2.4 millimetres (0.094 in) to 2.45 millimetres (0.096 in), with a carapace length of 1.05 millimetres (0.041 in) to 1.1 millimetres (0.043 in) and a width of 0.8 millimetres (0.031 in) and 0.85 millimetres (0.033 in). The abdomen is slightly bigger than the carapace with a length of 1.25 millimetres (0.049 in) to 1.3 millimetres (0.051 in). All somatic characters are the same as the female described earlier. However, on tibia II there is no prolateral spine and on tibia I the ventral spine is sometimes not present. The patella has a long curved dorsal spine. The pedipalps are highly distinctive from other spiders in the same family. On the patella there is a long and curved dorsal spine, and the tibia has one dorsal and two retrolateral trichobothria. The suprategulum has a broad, pointed suprategular apophysis, while the radix is heavily sclerotised distally and more lightly sclerotised towards the proximal end, which contains a looped duct and an elongated Fickert's gland. From the suprategulum the junction of radix and membrane, the median membrane arises. The membrane is lightly sclerotised proximally, featuring a long finger-like terminal process. The distal part of the membrane is more membranous and lies near the dorsal surface of the embolus, which is long and narrow with its distal part sclerotised and broadened forming lobes.
Distribution
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