A true Luciolinae fossil from the mid-Cretaceous Burmese amber provides new insights into the early evolution of fireflies (Coleoptera: Lampyridae)

Fireflies (Lampyridae) represent the most diverse terrestrial group of organisms capable of bioluminescence. However, their evolution remains inadequately understood due to the scarcity of early fossils. In this study, we uncover a new fossil genus and species, Cretoluciola birmana gen. et sp. nov., derived from a high-quality piece of the mid-Cretaceous Burmese amber. This new taxon is characterized by large eyes, filiform antennae, six abdominal ventrites and a bipartite light organ in males. It is robustly placed in the subfamily Luciolinae based on both maximum parsimony and Bayesian inference analyses (bootstrap results, with support values (BS) = 99.7%; posterior probabilities (PP) = 1.00), incorporating 410 morphological characters from 37 extant lampyrid genera plus the fossil taxon, and eight AHE loci from representative species. As the first definitive Cretaceous fossil, it establishes a minimum age constraint of 99 million years for Luciolinae, the crown group of Lampyridae. However, these findings cast doubt on the systematic placements of the other two fossil genera within Luciolinae, Flammarionella and Protoluciola, suggesting that the mid-Cretaceous Burmese fauna may have exhibited greater firefly diversity than previously recognized, at least at the subfamilial level. Furthermore, early fireflies are supposed to be nocturnal and adopt various survival and courtship strategies, thereby enhancing our understanding of the evolution of Lampyridae.