Phrynarachne birudissp. nov., a new crab spider (Araneae, Thomisidae) from South Korea

The preprints are preliminary versions of works accessible electronically in advance of publication of the final version. They are not issued for purposes of botanical, mycological or zoological nomenclature and are not effectively/validly published in the meaning of the Codes. Therefore, nomenclatural novelties (new names) or other nomenclatural acts (designations of type, choices of priority between names, choices between orthographic variants, or choices of gender of names) should NOT be posted in preprints. The following provisions in the Codes of Nomenclature define their status:


Introduction
The genus Phrynarachne Thorell, 1869 was erected with Phrynarachne rugosa (Walckenaer, 1805) as the type species. The genus currently consists of 32 species worldwide (World Spider Catalog 2021). Only one species, Phrynarachne katoi Chikuni, 1955, is known in Korea, and although rare, it is widely distributed throughout Korea (Fig.  1A) (Kim et al. 2016, Kim 2019, World Spider Catalog 2021. Two males of Phrynarachne birudis sp. nov. were collected from Gumi-si, Gyeongsangbuk-do (South-central inland area in South Korea) during an intensive seasonal investigation of the spider fauna in hilly province nationwide in 2019-2020 (Fig. 1B). The male of Phrynarachne birudis sp. nov. is described with measurements, a key to the males of Korean Phrynarachne species, morphological illustrations, and a distribution map.

Materials and methods
External morphology was examined and illustrated using a stereoscopic dissecting microscope (LEICA, S8APO, Singapore). Habitus photographs were taken with a CANON 650D with 60 mm macro-lens. Measurements of body parts were made with an ocular micrometer and are recorded in millimeters. Leg and palp (left) measurements are given as leg number, total length (femur, patella, tibia, metatarsus, tarsus). Abbreviations used are as follows: ALE = anterior lateral eye, AME = anterior median eye, PLE = posterior lateral eye, PME = posterior median eye, AER = anterior eye row, PER = posterior eye row; RTA = retrolateral tibial apophysis, VTA ventral tibial apophysis.

Diagnosis
The males of the new species can be easily distinguished from congeners of this genus by the large finger-like VTA with a bent tip and a thumb-like blunt RTA ( Fig. 3A-C); versus very short VTA with a very long and pointed RTA in P. brevis (Tang and Li 2010: 49, figs 35B-D), thumb-like VTA with a slightly bent tip and a very long and pointed RTA in P. ceylonica (Ono 1988: 25, figs 16, 17), thumb-like VTA without a bent tip and a very long and blunt RTA in P. jobiensis (Lehtinen 2016: 152, fig. 2g), thumb-like VTA without a bent tip and a very long and pointed RTA in P. katoi (Ono 1988: 28, figs 25, 26), thumb-like VTA with a slightly bent tip and a wide spear-like RTA in P. lancea, (Tang and Li 2010: 53, figs 37B-D), no VTA and a very long RTA with a slightly curved tip in P. melloleitaoi (Lessert 1933: 121, fig. 44), thumb-like VTA without a bent tip and a bifurcated RTA in P. rugosa (Ledoux 2004: 176, figs 19A-C).

Etymology
The species name is a combination of Latin prefix 'bi-' (means two) and noun 'rudis' (means small stick) referring to two small rod-like proximal protuberances on prolateral surface of the femur I.

Taxon discussion
A total of 32 species of the genus Phrynarachne Thorell, 1869 have been described around the world, of which only 10 species of males are known to date (World Spider Catalog 2021). The genus Phrynarachne is a species-rich one that has not been taxonomically revised comprehensibly in recent times. The males of the genus Phrynarache are generally similar in the shape of the tegulum and embolus. However, the known males can be easily distinguished from each other within this genus by the shape and size of a ventral tibial apophysis (VTA) and a retrolateral tibial apophysis (RTA) in the palpal organ.

Remarks:
The species was collected with a sweep net between shrubs in mixed forest of hilly terrain near the tributary of the Nakdonggang River. The new species appear to be endemic to South Korea. Currently, females have not been collected and are not known, and no ecological information is available for this species other than its habitat.

Identification keys
Key to the males of Korean Phrynarachne species