Zoosyst. Evol. 98 (1) 2022, 1-11 | DOI 10.3897/zse.98.76677 Gee Ee BERLIN Grismadox gen. nov., anew Neotropical genus of ant-resembling spiders (Araneae, Corinnidae, Castianeirinae), including the description of two new species from Bolivia and Paraguay Brogan L. Pett!:*°, Gonzalo D. Rubio**, Robert Perger® Coleccion Cientifica Para La Tierra, 321 Mariscal Estigarribia, Pilar, Neembuci, Paraguay DR FR Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn Campus, Penryn, Cornwall, TRIO 9FE, UK SpiDivERse, Biodiversity Inventory for Conservation (BINCO), Walmersumstraat 44, 3380 Glabbeek, Belgium Consejo Nacional de Investigaciones Cientificas y Técnicas (CONICET), Cerro Azul, Misiones, Argentina Estacion Experimental Agropecuaria Cerro Azul (EEA CA, INTA), Cerro Azul, Misiones, Argentina Nn oO KR W Coleccion Boliviana de Fauna, La Paz, Bolivia http://zoobank.org/CA75C8DB-013E-42D3-920F-654590CAFCAC Corresponding author: Brogan L. Pett (brogan.pett@outlook.com) Academic editor: Danilo Harms Received 17 October 2021 # Accepted 3 December 2021 @ Published 7 January 2022 Abstract A new genus and two new species of ant-resembling castianeirine spiders are described from the Neotropics. Grismadox gen. nov. comprises four species: Grismadox baueri sp. nov., and Grismadox mazaxoides (Perger & Duperré, 2021) comb. nov. from Bolivia, and Grismadox karugua sp. nov. (type species) and Grismadox mboitui (Pett, 2021) comb. nov. from Paraguay. All species are diag- nosed and the new species are described and illustrated. Available ecological data suggests that all four species are primarily epigeal and inhabit Grassland and savannah type habitats. Key Words ant-mimic, Chiquitano, Humid Chaco, myrmecomorph Introduction The subfamily Castianeirinae (Araneae, Corinnidae) 1s represented by slender spiders generally regarded as good examples of Batesian or Millerian mimics of ants (Cush- ing 2012; Perger and Rubio 2020; Perger 2021). The sub- family is cosmopolitan and the New World has a rich fau- na of accurate ant mimics with similar coloration to their ant models and adaptations to the typical body plan (ac- cording to concepts of Pekar and Jarab 2011). New World endemic genera include Mazax O. Pickard-Cambridge, 1898, Myrmecium Latreille, 1824, Myrmecotypus O. Pickard-Cambridge, 1894 and Pse/locoptus Simon, 1896 (World Spider Catalog 2021). The genera Apochinomma Pavesi, 1881, Castianeira Keyserling, 1879 and Spheco- typus O. Pickard-Cambridge, 1895 are recorded from the New World, but have intercontinental distributions, being registered from the Oriental Region, and the former two also from the Afrotropical realm (Haddad 2013; World Spider Catalog 2021). However, Apochinomma may be restricted to the Afrotropical realm, with Neotropical rep- resentatives likely misplaced (Rubio and Arbino 2009). Castianeirines are notorious for having highly conserved genitalic characters (Rubio et al. 2015), with both sexes showing a reduction or absence of various structures typical- ly found in related families of dionychan spiders (Ramirez 2014). However, in contrast to the genera Myrmecium and Mazax, which appear to be monophyletic (Reiskind 1969; Candiani and Bonaldo 2017), the variation in male genitalic structure of Myrmecotypus suggests a polyphyletic group Copyright Pett BL et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. 2 Pett, B.L. et al.: Grismadox gen. nov., a new Neotropical genus of ant resembling spiders (Reiskind 1969; Perger and Rubio 2020). The level of vari- ation exhibited in the embolus shape, length, and trajectory, as well as the presence or absence of a large to small con- ductor, retrolateral tibial apophyses (RTAs) of various sizes, including some large and distinct RTAs (Reiskind 1969; Pett 2021a), alludes to the hitherto undescribed generic diversity within the group. In contrast, female genitalia have always been described as relatively uniform in Myrmecotypus, with copulatory ducts joining the secondary spermathecae (ST II) and projecting posterolaterally (Reiskind 1969; Rubio and Arbino 2009; Perger and Rubio 2020). In the current study, two new castianeirine species are described from Bolivia and Paraguay. These species share a combination of several somatic and genitalic characters with Myrmecotypus mboitui Pett, 2021 and M. mazaxoi- des Perger & Dupérré, 2021 that is not found in other Neo- tropical castianeirines. The similarities between these four species and differences to Myrmecotypus species warrant the establishment of a new genus, herein described. Materials and methods Material is preserved in 70% ethanol. The epigyne was dissected using a custom-made hooked pin and digest- ed by submersion in a glass vial filled with lactic acid, which was placed in boiling water for around thirty min- utes. The cleared epigyne was temporarily prepared on a slide and examined with a compound microscope. Exam- inations were carried out with an AmScope ZM-4T ste- reomicroscope or an Olympus BX61. Images were taken using either a Leica M125C automontage system or an Olympus BX61 with a DP74 camera. All images were z-stacked, with between 10—30 images merged into a sin- gle photomontage, using Helicon Focus 6.7 (www.hel- iconsoft.com). Habitus illustrations were made by BLP using a ‘Wacom One’ graphics tablet with images under- laid at 60% opacity on the program ‘Autodesk Sketch- book’ (see: Cala-Riquelme 2021). Images were adjusted in Adobe Photoshop version 21.0.1 for contrast and white balance. Plates were also composed in Adobe Photoshop. The following indices are used following Reiskind (1969): A) carapace index = carapace width/ carapace length x 100; B) cephalic index = cephalic width/ car- apace width x 100; C) sternum index = sternum width/ sternum length