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Arachnids of the order Solifugae (solifuges, false spiders, sun spiders, camel spiders, Walzenspinne, wind spiders) possess the largest jaws for body size among the Chelicerata. The chelicerae provide the most important character systems for solifuge systematics, including dentition and the male cheliceral flagellum, both used extensively for species delimitation and diagnosis. However, the terminology used for cheliceral characters is not standardized and often contradictory, in part because it fails to represent homologous structures among taxa. Misinterpretation of character homology may introduce errors in phylogenetic analyses concerning relationships within Solifugae and among the orders of Chelicerata. This contribution presents the first comprehensive analysis of cheliceral morphology across the order Solifugae, the aims of which were to provide a broad survey of cheliceral characters for solifuge systematics, to identify and reinterpret structures based on primary homology, to revise the terminology to be consistent with homology hypotheses, and to provide a guide to terminological synonyms and character interpretations in the literature. Chelicerae were studied in 188 exemplar species (17% of the total), representing all 12 solifuge families, 17 of the 19 subfamilies, 64 genera (46% of the total), and the full range of variation in cheliceral morphology across the order. In total, 157 species representing 49 genera and 17 subfamilies are illustrated. Hypotheses of character transformation, particularly concerning the male flagellum, and a standardized terminology, are presented. The functional morphology of the chelicerae is discussed and the role of sexually dimorphic modifications to the male chelicerae in mating behavior emphasized. The revised terminology, based on hypotheses of primary homology, will facilitate solifuge revisionary systematics and provide a stronger basis for reconstructing phylogenetic relationships within the order Solifugae and testing the phylogenetic position of the order within Chelicerata.
