Morphology and phylogenetic implications of a genuine stonefly larva (Plecoptera: Perlidae) from mid-Cretaceous...

The family Perlidae is a diverse group of stoneflies frequently found in Mid-Cretaceous Kachin amber from northern Myanmar. However, no detailed descriptions of genuine perlid larvae from amber specimens have been reported. In this study, the first well-preserved genuine stonefly larva from Kachin amber is described and classified within the Perlidae. Morphological analysis reveals its closest affinity to larvae of the extant genus Caroperla Kohno, 1946 (subfamily Acroneuriinae, tribe Kiotinini), yet highlights unique traits suggesting affiliation with an undescribed lineage. Phylogenetic and morphospace analyses based on larval morphology consistently recover this fossil in an intermediate phylogenetic position, raising questions about the monophyly of subfamilies and tribes within Perlidae. Notably, the specimen exhibits functional adaptations such as predatory mouthparts and chloride cell-bearing gills identical to modern Perlidae, indicating morphological stasis since the mid-Cretaceous. This discovery not only underscores the critical role of amber in preserving aquatic immature stages but also provides novel insights into the evolutionary trajectories and ecological resilience of perlid larvae in ancient freshwater ecosystems.