A firefly relative that smelled and glowed: evidence for complex signalling systems in Cretaceous lampyroids

The evolution of insect sensory and signalling systems has played a key role in arthropod diversification, yet direct fossil evidence illuminating their early history remains rare. Lampyroids, including fireflies and their relatives, are notable for their elaborately modified antennae and bioluminescence. These characteristics make them an exceptional model for understanding the coevolution of sensory and signalling modalities. Here we describe Icaroramus perisi gen. et sp. nov. from mid-Cretaceous Kachin amber, a lampyroid beetle tentatively placed within Cretophengodidae. Icaroramus is exceptional in possessing both extraordinarily elaborate antennae and a well-developed photic organ. Its 12-segmented quadriheteroramose antennae represent an antennal architecture unknown among extant and fossil beetles. Functionally, these antennae likely combined an expanded olfactory surface area with differentiated sensory fields, enhancing the detection of pheromonal cues. Mate location was therefore probably mediated primarily by pheromones, whereas bioluminescence may have retained its plesiomorphic role in aposematic defence. This discovery expands the known morphological and ecological diversity of Cretaceous lampyroids and provides new insight into the origins of complex signalling strategies in fireflies and their relatives.