Bioacoustics of Magnacrus

Remark. Based on the examination of nearly all type species of ornithoctonine genera by Volker von Wirth, the presence of spines above the prolateral palp coxa suture are recognized as a synapomorphy. This character may be useful for dividing the subfamily Ornithoctoninae into two major clades. However, the result will be published in a separate study. Although, Magnacrus tongmianensis ( Zhu, Li & Song, 2002 ) gen. nov. comb. nov. , was original described under the genus Citharognathus , the new genus Magnacrus is separated from Citharognathus by: both male and female specimens of new genus without spines above the prolateral palp coxa suture ( Figs 1E , 2E , 5E , 7E ) vs. present in Citharognathus ( Figs 9E , 10E ); in females, there is a unique dense setal brush on the metatarsus of leg IV retrolaterally ( Figs 4A , 8A ) while absent in Citharognathus ( Fig. 12A ); there are no spinules on the carapace in Citharognathus ( Fig. 9A ); the strongly incrassate patella, tibia and metatarsus of legs III and IV compared to legs I and II ( Figs 4A , 8A ) while in Citharognathus only the tibia of leg IV is incrassate ( Fig. 12A ); there are numerous short, stout black spinules on patellae, tibiae and metatarsi of leg III & IV in C. hosei ( Figs 9C , 12A , 13B ), but absent in the new genus Magnacrus . Additionally, male Citharognathus possess distinct long dense setae on all legs and abdomen ( Fig. 12B ) while this feature is less distinct in male Magnacrus ( Figs 4B , 8B ). Thus, we propose the new ornithortonine genus Magnacrus gen. nov. , to accommodate the new combination M. tongmianensis ( Zhu, Li & Song, 2002 ) gen. nov. comb. nov. , and the new species M. taynguyenensis gen. nov. sp. nov. , both from Vietnam . Additionally, the two genera show differences in both distribution and lifestyle species as Magnacrus are currently known only from the Central Highlands of Vietnam and are typical ground-dwelling spiders ( Figs 14A–D , 15A–B ), whereas the type species of Citharognathus , C. hosei , is an arboreal species distributed in northern Borneo ( Fig. 16 A–B ). Although both genera show an incrassate tibia of leg IV, the thickened posterior legs are not rare for Theraphosids, and this trait is usually of multiple independent origins, such as those genera of the theraphosinae, Eupalaestrus Pocock, 1901 , Crassicrus Reichling & West, 1996 ( Reichling & West 1996 ; Borges et al. 2021 ). At first glance, this feature seems to closely link Magnacrus and Citharognathus . However, the presence of spinules above the maxillary suture and the presence of numerous short, stout black spinules on patella, tibia and metatarsus of leg III & IV in Citharognathus ( Figs 9C , 12A , 13B ) as well as their geographical distribution and lifestyle, suggest that their phylogenetic positions are actually quite distant from each other (Wendt et al. in prep.)