Early evolution of Rhopalidae (Hemiptera): the first amber-preserved “scentless bug” from Myanmar with phylogenetic implications

As an important group within the superfamily Coreoidea, extant Rhopalidae are commonly dubbed “scentless bugs” due to the degeneration of their scent glands, yet their early evolutionary history and phylogenetic relationships have long remained enigmatic. This study integrates fossil evidence with morphological analyses of Rhopalidae Odorocoris longirostris sp. nov., the first rhopalid species discovered in mid-Cretaceous Kachin amber, clarifying the intrafamilial phylogeny. Results demonstrate that: (i) Originicorizus (Yao et al. 2006a, 2006b) and Quatlocellus (Yao et al. 2006a, 2006b) (165 million years ago) represent the oldest-known stem-group rhopalids, retaining plesiomorphic traits including the presence of vein C and a lanceolate ovipositor. (ii) The new Kachin amber genus Odorocoris gen. nov. has a mosaic of character states typical of Serinethinae and Rhopalinae, providing empirical evidence for the paraphyly of the latter and supporting the reclassification of Serinethinae as a tribal-level taxon (Serinethini stat. nov.). (iii) The character states of fossil groups reveal that evolutionary transitions—degeneration of vein C (Jurassic to mid-Cretaceous), transformation of the ovipositor from lanceolate to plate-like (post mid-Cretaceous), and degeneration of scent glands—were synchronous with niche differentiation during the gymnosperm-to-angiosperm transition. In summary, this study reconstructs the evolutionary framework of Rhopalidae using Kachin amber fossils while illuminating the ecological coevolutionary mechanisms between key morphological transitions and the angiosperm radiation.