High-level systematics and phylogeny of the extant scorpions (Scorpiones: Orthosterni)

A number of authors (e. g. Birula, 1917a, 1917b; Mello-Leitão, 1945; Stockwell, 1989) addressed above-level systematics of extant scorpions, and accepted the grouping of scorpion families in several superfamilies. At the same time, Kjellesvig-Waering (1986) classified all extant scorpions under the same superfamily, Scorpionoidea. Sissom (1990) and Fet et al. (2000) did not list any superfamilies, considering the systematic situation above family (and often at the family level as well) unresolved. Most recently, Lourenço (2000a) listed six superfamilies, largely following the unpublished but important study of Stockwell (1989). The goal of this paper is to address scorpion systematics and phylogeny above genus level. We conducted a comprehensive, cladistic morphological analysis of 90 extant genera (over 150 species) of scorpions belonging to all recognized families. We especially concentrated on relationships among so-called “chactoid” scorpions, where subfamilies, tribes, and subtribes were revised and/or established. The family Chactidae was given a special attention due to the number of phylogenetic and taxonomic issues that were revised. In addition, we addressed the status of a recently discovered, unique relict family Pseudochactidae, and the systematic relationships within Iuridae. As a result of intensive study, we propose a number of sweeping changes in current scorpion taxonomy; the results of analyses leading to these changes are discussed in detail. The category of parvorder, subordinate to infraorder, is introduced for the first time in arachnid systematics. Four extant parvorders are recognized within the scorpion infraorder Orthosterni: Buthida, Chaerilida, Pseudochactida, and Iurida. Six extant superfamilies are recognized: Buthoidea, Chactoidea (=Vaejovoidea, syn. n), Chaeriloidea, Iuroidea (new), Pseudochactoidea (new), and Scorpionoidea (=Bothriuroidea, syn. n). Parvorders Buthida, Chaerilida and Pseudochactida are monotypic, each including a single superfamily; parvorder Iurida includes three superfamilies (Chactoidea, Iuroidea, and Scorpionoidea). We recognize 14 extant scorpion families: Bothriuridae, Buthidae, Caraboctonidae, Chactidae, Chaerilidae, Euscorpiidae, Iuridae, Liochelidae, Microcharmidae, Pseudochactidae, Scorpionidae, Superstitioniidae, Urodacidae, and Vaejovidae. Superfamilies Chaeriloidea and Pseudochactoidea are monotypic; superfamily Buthoidea includes two families (Buthidae and Microcharmidae). Superfamily Iuroidea includes two families (Caraboctonidae and Iuridae); subfamily Caraboctoninae (formerly in Iuridae) is elevated to the family rank. Superfamily Chactoidea includes four families: Chactidae, Euscorpiidae, Superstitioniidae (=Troglotayosicidae, syn. n), and Vaejovidae. Within Chactidae, three subfamilies are established: Chactinae, Brotheinae, and Uroctoninae. Within Chactinae, two tribes are established: Chactini and Nullibrotheini, new tribe (monotypic). Within new subfamily Brotheinae, two tribes are established: Brotheini and Belisariini (monotypic). Within Brotheini, two subtribes are established: Brotheina and Neochactina, new subtribe; the latter is based on