<br> The genus<br> Crassignatha<br> Wunderlich, 1995, represents the second most species-rich lineage within the spider family Symphytognathidae. Members of the genus are predominantly distributed in southwestern China and Southeast Asia, with the exception of<br> C.kishidai<br> (Shinkai, 2009), which is recorded from Japan. Historically, the circumscription and diagnosis of<br> Crassignatha<br> have remained ambiguous, and its monophyly has not yet been rigorously tested. In this study, we conducted a molecular phylogenetic analysis based on sequence data from five genetic markers (16S, 18S, 28S, H3, and a fragment of COI) to evaluate the monophyletic status of the genus. Sequences were obtained from 21 species of<br> Crassignatha<br> (ingroup), along with two species of<br> Kirinua<br> Li & Lin, 2021, and one species of<br> Patu<br> Marples, 1951, as the outgroup. The results support the monophyly of<br> Crassignatha<br> and confirm the taxonomic validity of the 21 included species. Five species of<br> Crassignatha<br> belonging to Symphytognathidae are reported from the Yunnan–Guizhou Plateau, four of which are newly described:<br> C. hekou<br> Wu & Lin,<br> sp. nov<br> . (♂♀),<br> C. qingxu<br> Wu & Lin,<br> sp. nov<br> . (♂♀),<br> C. liangdu<br> Wu & Lin,<br> sp. nov<br> . (♂♀), and<br> C. panlong<br> Wu & Lin,<br> sp. nov<br> . (♂♀). Additionally, a new distribution record outside the type locality is provided for the previously known species<br> C. shunani<br> Lin & S. Q. Li, 2020 (♂♀). Detailed diagnoses, descriptions, and illustrations are provided for all newly described species. The geographic distribution of<br> Crassignatha<br> is also discussed.<br>