Bioacoustics of Acanthoscurria theraphosoides

Remarks. Prior to the present contribution, RG, while examining specimens for other papers on Acanthoscurria ( i.e., Paula et al ., 2014 ; Gabriel, 2020), concluded the genus Acanthoscurria contained five distinct groups of species, based on genital organ morphology, though grouped merely by the presence of a stridulation organ and a prolaterally-situated male tibial apophysis. He concluded that use of the stridulation organ as a generic-level character as proposed by Pocock (1901 , 1903 ) and most other authors underestimate diversity as this character does not show the marked variation seen in the genitalia of Acanthoscurria species of which separate lineages can be recognised. RG shared this information with DS, who concurred. Furthermore, RG suspected they could represent a new subfamily within Theraphosidae , but that is outside the scope of this work. We have since worked for more than a decade on the genus with collaborators and continually re-examined type material as we discovered new characters. Naming the present species-group is the first step towards future work on these lineages.

Diagnosis. Males of the theraphosoides species-group ( Figs 1–5 ) are readily distinguished from other Acanthoscurria including the type species ( Fig. 6 ) by the presence of a forward-pointing, digitiform, retrolateral palpal tibial apophysis, strongly incrassate palpal tibia, palpal bulb with an incrassate paraembolic apophysis, presence of a subapical granular area, enlarged prolateral accessory inferior keel, and absence of a prolateral accessory central keel and retrolateral pad of plumose stridulatory setae on femur IV (developed or well-developed triangular retrolateral palpal tibial apophysis, slightly or not incrassate palpal tibia, presence of retrolateral pad of plumose stridulatory setae on femur IV, palpal bulb with prolateral accessory central keel, and absence of an incrassate paraembolic apophysis, and no subapical granular area or prolateral accessory inferior keel in the rest of Acanthoscurria ) ( Paula et al. 2014 ; Galleti-Lima & Guadanucci, 2019 ; Gabriel, 2020). Indeed, the following combination of characters separate males of the theraphosoides species-group from all other known theraphosine genera:(1) single, prolaterally-situated, tibial apophysis; (2) prolateral superior keel enlarged and dorso-retrolaterally positioned; (3) enlarged prolateral accessory inferior keel extending from distal section [not apical] to area of paraembolic apophysis; (4) forward-pointing digitiform tegular apophysis; (5) short apical keel with absence of a subapical keel; (6) presence of claviform stridulatory setae on trochanters, and (7) presence of regular Type I urticating setae. Females of the theraphosoides species-group differ from all other theraphosine genera by a combination of (1) a basally fused, short and wide, membranous bursa copulatrix with two receptacles dorsally positioned (apically positioned in the rest of Acanthoscurria ); (2) presence of claviform stridulatory setae on trochanters, and (3) having regular Type I urticating setae (for illustrations of female morphology, see Paula et al ., 2014 ).