Triaenonychidae is a family of Opiliones with almost 500 described species distributed in the southern continents. Recent work has provided a solid phylogenetic foundation based on Sanger and ultraconserved element molecular sequence data that resulted in a global reorganisation of the family. In this study, we turn to the South American triaenonychids, aggregating sequences of three markers (18S rRNA, 28S rRNA and cytochrome c oxidase subunit I), re-examining the position of additional South American species and confirming the existence of a new genus. We provide novel information regarding the external morphology of 10 of the 11 South American genera of Triaenonychidae, based on stereomicroscope and SEM images of the body and genitalia. In addition, a new genus Adrianonyx gen. nov. and two new species, Adrianonyx contulmo sp. nov. from the Monumento Natural Contulmo (Chile) and Adrianonyx crypticus sp. nov. from the Parque Nacional Nahuelbuta (Chile) are described.