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A new genus and species of short-tailed whipscorpion (Schizomida: Hubbardiidae Cook, 1899) is described based on specimens collected in the Venezuelan state of Amazonas. The new genus differs from other Neotropical genera in the presence of six setae on opisthosomal tergite II, the absence of seta Dm4 on the flagellum in both sexes, the female flagellum comprising four segments, and the median lobes of the spermatheca being four times longer than the lateral lobes. Jipai longevus gen. et sp. nov. increases the count of South American schizomid genera to fourteen and the count of species to 57. The type locality of the new taxon is situated in the Guiana region of Amazonia s. l., where three other hubbardiid genera have also been recorded. This discovery contributes to the understanding of Amazonian schizomid diversity and highlights the need for further sampling in this diverse, vulnerable and poorly explored area. 

Thelyphonida Blanchard, 1852, also known as vinegaroons or whip-scorpions, is a small arachnid order with 140 described species contained in a single family, Thelyphonidae Lucas, 1835. Despite being conspicuous and widely distributed across the tropics and subtropics on four continents, knowledge of the order has been slow to advance. Hypoctoninae Pocock, 1899, one of four subfamilies currently recognized and one of two represented in the New World, comprises five genera. Since its inception, Thelyphonellus Pocock, 1894 has remained the only hypoctonine genus occurring in South America, with only four species described prior to the present contribution. The first detailed morphological study and phylogenetic analysis of Thelyphonellus is presented herein. The morphological phylogenetic analysis—the first for Thelyphonida—includes all except one of the previously described species of Thelyphonellus in addition to two new species described herein; the species of Ravilops Víquez and Armas, 2005 (from the Caribbean island of Hispaniola); and the monotypic Old World genus Etienneus Heurtault, 1984 (from West Africa) scored for 45 morphological characters. A single, most parsimonious phylogenetic hypothesis revealed that Thelyphonellus is paraphyletic with respect to Ravilops. The New World Hypoctoninae comprises four clades with disjunct distributions and well supported by a combination of morphological characteristics, on the basis of which four genera, two of which are new, are recognized: Ravilops, with two species, endemic to Hispaniola; Thelyphonellus, herein restricted to Thelyphonellus amazonicus (Butler, 1872) and Thelyphonellus ruschii Weygoldt, 1979, occurring in Guyana, Suriname, French Guiana, and northern Brazil; Wounaan, gen. n., containing Wounaan vanegasae (Giupponi and Vasconcelos, 2008), comb. n. and Wounaan yarigui, sp. n. from Colombia; and Yekuana, gen. n., containing Yekuana venezolensis (Haupt, 2009), comb. n. and Yekuana wanadi, sp. n. from Venezuela. The two new species are described and illustrated. A key to the identification of the Neotropical genera of Hypoctoninae and a map plotting the known distribution of its species are also presented. 

Background/Objectives: Arachnids are a megadiverse arthropod group. The present study investigated the chromosomes of pedipalpid tetrapulmonates (orders Amblypygi, Thelyphonida, Schizomida) and two arachnid orders of uncertain phylogenetic placement, Ricinulei and Solifugae, to reconstruct their karyotype evolution. Except for amblypygids, the cytogenetics of these arachnid orders was almost unknown prior to the present study. Methods: Chromosomes were investigated using methods of standard (Giemsa-stained preparations, banding techniques) and molecular cytogenetics (fluorescence in situ hybridization, comparative genomic hybridization). Results and Conclusions: New data for 38 species, combined with previously published data, suggest that ancestral arachnids possessed low to moderate 2n (22–40), monocentric chromosomes, one nucleolus organizer region (NOR), low levels of heterochromatin and recombinations, and no or homomorphic sex chromosomes. Karyotypes of Pedipalpi and Solifugae diversified via centric fusions, pericentric inversions, and changes in the pattern of NORs and, in solifuges, also through tandem fusions. Some solifuges display an enormous amount of constitutive heterochromatin and high NOR number. It is hypothesized that the common ancestor of amblypygids, thelyphonids, and spiders exhibited a homomorphic XY system, and that telomeric heterochromatin and NORs were involved in the evolution of amblypygid sex chromosomes. The new findings support the Cephalosomata clade (acariforms, palpigrades, and solifuges). Hypotheses concerning the origin of acariform holocentric chromosomes are presented. Unlike current phylogenetic hypotheses, the results suggest a sister relationship between Schizomida and a clade comprising other tetrapulmonates as well as a polyploidization in the common ancestor of the clade comprising Araneae, Amblypygi, and Thelyphonida.