Triaenonychidae Sørensen in L. Koch, 1886 is a large family of Opiliones with ~480 described species broadly distributed across temperate forests in the Southern Hemisphere. However, it remains poorly understood taxonomically, as no comprehensive phylogenetic work has ever been undertaken. In this study we capitalise on samples largely collected by us during the last two decades and use Sanger DNA-sequencing techniques to produce a large phylogenetic tree with 300 triaenonychid terminals representing nearly 50% of triaenonychid genera and including representatives from all the major geographic areas from which they are known. Phylogenetic analyses using maximum likelihood and Bayesian inference methods recover the family as diphyletic, placing Lomanella Pocock, 1903 as the sister group to the New Zealand endemic family Synthetonychiidae Forster, 1954. With the exception of the Laurasian representatives of the family, all landmasses contain non-monophyletic assemblages of taxa. To determine whether this non-monophyly was the result of Gondwanan vicariance, ancient cladogenesis due to habitat regionalisation, or more recent over-water dispersal, we inferred divergence times. We found that most divergence times between landmasses predate Gondwanan breakup, though there has been at least one instance of transoceanic dispersal – to New Caledonia. In all, we identify multiple places in the phylogeny where taxonomic revision is needed, and transfer Lomanella outside of Triaenonychidae in order to maintain monophyly of the family.

Promecostethus unifalculatus Enderlein, 1909, is the only representative of the order Opiliones from the Crozet Islands. The species belongs to the family Triaenonychidae and is biogeographically interesting because it is a candidate for transoceanic dispersal, a very rare event in this ancient family. Despite this significance, P. unifalculatus is taxonomically still poorly known, and a redescription of this species using modern taxonomic standards is urgently needed. Here we redescribe the species, offer the first description and illustrations of the male genitalia and provide a full exomorphological survey of the species using scanning electron microscopy. Furthermore, we provide an emended diagnosis for the genus Promecostethus and discuss its relationship with some morphologically similar genera.

The genus Nuncia has long been the most speciose within the Opiliones family Triaenonychidae, comprising 63 species and subspecies distributed across New Zealand and South America. Recent molecular studies utilizing Sanger sequencing and ultraconserved elements (UCEs) have indicated that this genus is not monophyletic, and true Nuncia are actually confined to New Zealand. Here, the morphology of all South American triaenonychids is re-examined and DNA sequence data compiled from three markers (18S rRNA, 28S rRNA and cytochrome c oxidase subunit I) for a large number of triaenonychid species, including specimens from all areas with species currently and formerly classified in Nuncia to reassess their phylogenetic position. Based on our findings we 1) revalidate the genus Chilenuncia (Muñoz-Cuevas, 1971) nom. rest.; 2) describe five new genera: Fresiaxgen. nov., Mistraliagen. nov., Laftrachiagen. nov., Lautariagen. nov., Nerudiellagen. nov.; 3) redescribe five species: Fresiax spinulosacomb. nov., Mistralia verrucosacomb. nov., Chilenuncia chilensiscomb. nov., Chilenuncia rostratacomb. nov., Nerudiella americanacomb. nov.; and 4) describe 22 new species of South American triaenonychids: Fresiax conicasp. nov., Fresiax fraysp. nov., Fresiax mauryisp. nov., Fresiax pichicuysp. nov., Mistralia ramirezisp. nov., Laftrachia robinsp. nov., Lautaria ceacheisp. nov., Nerudiella cachaisp. nov., Nerudiella caramavidasp. nov., Nerudiella cautinsp. nov., Nerudiella choapasp. nov., Nerudiella curisp. nov., Nerudiella goroisp. nov., Nerudiella jaimeisp. nov., Nerudiella mallecosp. nov., Nerudiella pencosp. nov., Nerudiella pichisp. nov., Nerudiella portaisp. nov., Nerudiella quenessp. nov., Nerudiella vilchessp. nov., Nerudiella wekufesp. nov., and Nerudiella zapallarsp. nov. Furthermore, we provide detailed illustrations of all the South American species belonging to these lineages formerly classified in Nuncia.