Abba, a new monotypic genus of orb-weaving spiders (Araneae, Araneidae) from Australia Author Castanheira, Pedro de S. https://orcid.org/0000-0002-0623-1622 Harry Butler Institute, Murdoch University, 90 South St, Murdoch, Western Australia 6150, Australia pedrocastanheira.bio@gmail.com Author Framenau, Volker W. https://orcid.org/0000-0002-7724-3831 Harry Butler Institute, Murdoch University, 90 South St, Murdoch, Western Australia 6150, Australia & Department of Terrestrial Zoology, Western Australian Museum, Locked Bag 49, Welshpool DC, Western Australia, 6986, Australia & Zoological Museum Hamburg, Leibnitz Institute for the Analysis of Biodiversity Change (LIB), Centre for Taxonomy & Morphology, Martin-Luther-King-Platz 3, 20146 Hamburg, Germany text Evolutionary Systematics 2023 2023-01-16 7 1 73 81 http://dx.doi.org/10.3897/evolsyst.7.98015 journal article http://dx.doi.org/10.3897/evolsyst.7.98015 2535-0730-1-73 E51A70F73E3846EA9AA39376EA6C9D0C 2242C2CBF33C5774973E7C0741638C1B Abba gen. nov. Type species. Araneus transversus Rainbow, 1912. Designated here. Etymology. The genus-group name honours the Swedish pop group ABBA whose songs and subsequent musicals Mamma Mia! (2008) and Mamma Mia - Here We Go again! (2018), provided hours of entertainment for the authors. The gender of the genus-group name is feminine. Diagnosis. Abba gen. nov. can be diagnosed by the set of strong prolateral macrosetae on the first tibia of the males and by the distinct colouration of the abdomen in both the males and females, consisting of a pair of dark spots centrally on a uniformly creamy-white to grey dorsal surface (Figs 1A , 3 , 4A ). Figure 1. Abba transversa (Rainbow, 1912) comb. nov., male (QM S88101). A , dorsal habitus; B , ventral habitus; C , left pedipalp, ventral view; D , left pedipalp, dorsal view. Scale bars: 1 mm ( A , B ); 0.1 mm ( C , D ). Description. Small orb-weaving spiders, males (total length ca. 3.0-3.5) smaller than females (total length ca. 4.0-4.5). Carapace longer than wide, pear-shaped and with cephalic region comparatively narrower in males than in females; colouration yellowish-brown (green in live specimens), generally without setae (Figs 1A , 4A ). Fovea transverse in males and females. Anterior median eyes largest, row of posterior eyes slightly recurved, lateral eyes almost touching; lateral eyes on joint tubercles but the row of the posterior lateral eyes slightly wider than that of the anterior lateral eyes; anterior median eyes slightly protruding from the carapace (Figs 1A , 4A ). Maxillae subquadrate, yellow with anterior dark border (Figs 1B , 4B ). Sternum longer than wide, yellow, with a sparse cover of setae (Figs 1B , 4B ). Labium wider than long, with anterior glabrous light edge (Figs 1B , 4B ). Chelicerae fangs with three promarginal teeth of similar size, and three retromarginal teeth of similar size. Legs: Leg formula I> IV> II> III; males with set of ca. five strong prolateral macrosetae on the first tibia (Figs 1A , 3 ). Abdomen slightly longer than wide, somewhat dorso-ventrally compressed, oval, without humeral humps, specialized setae, sigilla, condyles or other specific structures; colour dorsally varying from beige to grey, bearing two centrally located dark spots (Figs 1A , 4A ). Venter grey, sparse layer of guanine crystals (Figs 1B , 4B ). Male pedipalp patella with two macrosetae (Fig. 1C, D ); paracymbium elongated and hook-like (Figs 1D , 2B ); median apophysis subquadrate spatulate, with strong sclerotized finger-like tip and sclerotized base (Figs 1C , 2A, B ); radix poorly developed (Figs 1C , 2A ); terminal apophysis wider than long, rounded with sclerotized tip (Figs 1C, D , 2A, B ); conductor elongate, membranous, apically slightly curved (Figs 1C, D , 2A, B ); embolus heavily sclerotized and thick, curved basally, uncapped (Figs 1C, D , 2A, B ). Epigyne base rounded, lateral portion rounded and heavily sclerotized; atrium wide and heavily sclerotized with copulatory openings located posteriorly (Fig. 4C, D ); scape approximately as long as atrium length, not exceeding posterior epigyne base, with terminal pocket (Fig. 4C ); spermathecae ovoid to spherical, larger than atrium (Fig. 4C-E ).