Terry Pratchett's Anelosimus

The total length of the spider is approximately 2.4 to 3.6 millimetres (0.094 to 0.142 in), with females slightly larger than the males. The colouration pattern is similar to others in its genus: the prosoma is light yellow with grey lines, while the abdomen is lighter in colour with spots clustering off the midline. Its primary diagnostic characteristic is the shape of the genitals. In males, the embolus is corkscrew-shaped. A similar shape is found in Anelosimus luckyi, although the embolus is longer in A. pratchetti. The female can be distinguished from others in the genus by the shape of the copulatory ducts and a unique triangular epigynal plate.

The holotype specimen was collected from Berowra Valley Regional Park, at an elevation of approximately 100 metres (330 ft). Additional specimens have been collected from Toolijooa at elevations of approximately 0 to 5 metres (0 to 16 ft). The species has only been found in Australia. The holotype and several paratypes were curated by the National Museum of Natural History. The species' uniqueness and placement in the genus has been confirmed by analysis of nuclear and mitochondrial DNA. Phylogenetic analysis indicates a closer link between Anelosimus pratchetti and two Madagascar species, Anelosimus sallee and Anelosimus may, than several geographically closer species within the same genus. The species on Madagascar have previously been identified as arriving in multiple migration events. The finding further illustrates the complexity of migration within the genus.