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Systematics provides the foundational knowledge about the units of biodiversity, i.e., species, and how we classify them. The results of this discipline extend across Biology and can have important impacts on conservation. Here we review the systematic and taxonomic practices within Theraphosidae over the last 260 years. We examine the rate of newly described species and investigate the contemporary practices being used in the description of new genera and species. There have been two large waves of theraphosid taxonomy, with an explosive growth of newly described species and author combinations in the last 60 years. We look back and find that during 2010–2024 contemporary practices in theraphosid systematics and taxonomy have remained largely static, being dominated by morphology-based approaches. Over this period, only 10% of newly described species incorporated DNA data or explicitly stated the species concept used. Similarly for genera, only five of the 37 newly described genera over that time were supported as distinct and monophyletic by DNA. We highlight the taxonomic movement of species among Theraphosidae, Barychelidae, and Paratropididae; however, given the limited molecular sampling for the two latter families, the boundaries of these families remain a significant area of needed research. To promote inclusivity, we provide a copy of this paper in Spanish as supplementary material. 

The Chiricahua Mountains in southeastern Arizona are renowned for their exceptional biodiversity and high levels of endemism. Morphological, genomic, behavioral, and distributional data were used to report the discovery of a remarkable new tarantula species from this range.Aphonopelma jacobiisp. nov.inhabits high-elevation mixed conifer forests in these mountains, but also co-occurs and shares its breeding period withA. chiricahua—a related member of theMarxispecies group—in mid-elevation Madrean evergreen oak and pine-oak woodlands. This marks the first documented case of syntopy between two montane endemics in the Madrean Archipelago and adds to our knowledge of this threatened region’s unmatched tarantula diversity in the United States. An emended diagnosis and redescription forA. chiricahuaare also provided based on several newly acquired and accurately identified specimens. Phylogenetic analyses of mitochondrial and genomic-scale data reveal thatA. jacobiisp. nov.is more closely related toA. marxi, a species primarily distributed on the Colorado Plateau, than toA. chiricahuaor the other Madrean Sky Island taxa. These data provide the evolutionary framework for better understanding the region’s complex biogeographic history (e.g., biotic assembly of the Chiricahua Mountains) and conservation of these spiders. 

Theraphosinae is the most diverse subfamily of Theraphosidae spiders, but their evolutionary history remains unresolved to date. This problem is common in taxonomic groups with phylogenetic hypotheses that have often been based only on qualitative morphological characters and, rarely, on molecular analyses. Phylogenomics has significantly contributed to the understanding of the evolution of many non-model groups, such as spiders. Herein, we employed ultraconserved elements (UCEs) phylogenomics to propose a new hypothesis for a group of Theraphosinae genera, namely Lasiodoriforms:Vitalius, Lasiodora, Eupalaestrus, Pterinopelma, Proshapalopus, andNhandu. We propose three genera and their respective morphological diagnoses are provided. Our phylogeny supports the transfer of species from the genusVitaliustoPterinopelmaandProshapalopusand fromProshapalopustoEupalaestrus. Finally, we describe a new species ofVitaliusfrom Southern Brazil. Based on these three new generic descriptions and transferred species, the Lasiodoriform tarantulas comprise nine genera from Argentina, Brazil, Paraguay, and Uruguay, and the genusVitaliusnow includes seven species.