Chactoidea Pocock, 1893

Soleglad, Michael E. & Fet, Victor, 2003, High-level systematics and phylogeny of the extant scorpions (Scorpiones: Orthosterni), Euscorpius 2003 (11), pp. 1-175 : 93-94

Superfamily Chactoidea Pocock, 1893

Type Genus. Chactas Gervais, 1844 .

Synonyms.

Vaejovoidea Thorell, 1876, new synonymy (valid as family name).

Composition. We include under Chactoidea four families: Chactidae , Euscorpiidae , Superstitioniidae , and Vaejovidae . The content of Chactoidea is changed here compared to that of Lourenço (2000a): we include here family Vaejovidae , and the superfamily Vaejovoidea is synonymized with Chactoidea . Family Iuridae is placed in superfamily Iuroidea , with the exception of genus Anuroctonus , which is transferred from Iuridae to Chactidae . The following new changes are also enforced within Chactoidea : family Troglotayosicidae is synonymized with Superstitioniidae , and its two genera are transferred to Superstitioniidae ( Troglotayosicus ) and Chactidae ( Belisarius ); genus Uroctonus is moved from Vaejovidae to Chactidae ; and a new arrangement of subfamilies, tribes, and subtribes is established in Chactidae .

Distribution. Europe, Asia, Africa ( Euscorpius ; Mediterranean Sea coast), North America, Central and South America.

Taxonomic history. The taxonomic history of this superfamily is complicated and confusing; see Sissom (2000a) for details. The name was used first by Birula (1917a, 1917b), and embraced Chactidae (which also then included taxa currently assigned to Euscorpiidae and Chaerilidae ), Vaejovidae (which also then included taxa currently assigned to Euscorpiidae and Iuridae ), and, in addition, Bothriuridae . The separate status of Bothriuridae was soon recognized, and this family was excluded from Chactoidea by Mello-Leitão (1945). Placement of Chaerilidae in Chactoidea persisted until Vachon (1956, 1963, 1974) demonstrated a separate trichobothrial “ Type B” for Chaerilidae . Lamoral (1980: 443) suggested that Chactidae and Vaejovidae should be lumped further together into one family. Relationships among these families remained unclear until recently; Sissom (1990) treated Chactidae (in broad sense, including current Euscorpiidae and Superstitioniidae ) and Vaejovidae together in his key, for practical purposes designed without familial distinctions. Stockwell (1989) recognized Chactoidea as including Chactidae , Euscorpiidae , and Scorpiopsidae , but listed Superstitioniidae under Vaejovoidea , which also included Iuridae . Stockwell (1992) formally established Euscorpiidae , Scorpiopsidae , and Superstitioniidae as separate families. Lourenço (2000a), who followed unpublished classification of Stockwell (1989), listed five families in Chactoidea ( Chactidae , Euscorpiidae , Scorpiopsidae , Superstitioniidae , and Troglotayosicidae ) and two families in Vaejovoidea ( Iuridae and Vaejovidae ). Until recently, many authors indicated that separation of Vaejovidae from Chactidae and related families was problematic ( Sissom, 2000a).

Biogeographic history. Our phylogenetic analysis demonstrates the relationship between chactoid families as ((( Euscorpiidae , Chactidae ), Superstitioniidae ), Vaejovidae ). Two of these families ( Chactidae and Euscorpiidae ) incorporate both New World and Old World taxa, while Superstitioniidae and Vaejovidae are found only in the New World. However, this modern distribution is not sufficient to suggest New World origin of Chactoidea . Significant disjunctions between Old World and New World taxa of Chactidae and Euscorpiidae , sometimes at the subfamily level ( Brotheinae and Scorpiopinae ), cannot be explained by the Gondwanaland breakup or by dispersal, and suggest that these ancient lineages existed already in the Pangean times. The only known fossil chactoid is a presumably Oligocene vaejovid from Mexico (Santiago-Blay et al., 2001). The Cretaceous family Palaeoeuscorpiidae , included in Chactoidea by Lourenço (2003), is treated here as parvorder Iurida incertae sedis (see below). A complete absence of Afrotropical and Australian taxa is peculiar for Chactoidea .

Diagnosis. Synapomorphies. Dorsal edge of cheliceral movable finger with two subdistal denticles; ventral surface of leg tarsus configured with moderately developed setal pairs and a median spinule row; hemispermatophore capsule present, weak to moderate development; genital papillae of male visible at posterior edge of genital operculum. Important Symplesiomorphies. Ventral edge of cheliceral movable finger smooth; median denticle (MD) row of chelal finger aligned in straight line; sclerites of genital operculum of female generally fused; chela with “10-carinae” configuration.

Discussion. An interesting but not generally known fact is that the generic name Chactas was given after the literary character, a Native American youth of Natchez tribe in a famous romantic novel Atala by the French writer Chateaubriand, published in 1801.

Characters used to delineate the four chactoid families involve positions of trichobothria on the pedipalp chelae and patellae, the fundamental configuration of the chelal finger median denticle (MD) row, presence or absence of accessory denticles on the chelal fingers, neobothriotaxy, and the overall carinal development and shape of the chelal palm.