X‐ray microtomography and phylogenomics provide insights into the morphology and evolution of an enigmatic Mesozoic insect larva

Fossils sometimes show unusual morphological features absent in living organisms, making it difficult to reconstruct both their affinity and their function. We describe here a new lacewing larva, Ankyloleon caudatus gen. et sp.n. (Neuroptera) from the Cretaceous amber of Myanmar, characterized by an abdomen unique among insects, with ‘tail‐like’ terminal segments bearing a ventral pair of vesicles. Phase‐contrast X‐ray microtomography reveals that these structures were dense and equipped with a median duct, suggesting that they were likely pygopods used for locomotion, holding the position through adhesive secretions. Our phylogenetic analyses, combining genomic and morphological data from both living and fossil lacewings, proved critical to placing Ankyloleon gen.n. on the lacewing tree of life as an early representative of the antlion clade, Myrmeleontiformia. These results corroborate the view that derived myrmeleontiform lacewings ‘experimented’ with unusual combinations of features and specializations during their evolutionary history, some of which are now lost. Zoobank registration: urn:lsid:zoobank.org:pub:0C0AC565‐1AC9‐42CC‐831D‐EDA38BA36F64 A new, morphologically unique lacewing larva from Cretaceous amber of Myanmar (Kachin state) is described and rendered using X‐ray phase‐contrast microtomography. The phylogenetic analysis integrating morphological and genomic data from extant and extinct taxa recovers this larva near antlions, corroborating the Cretaceous as an evolutionary experimentation phase in lacewings. Microtomographic scans showed that the larva had a peculiar tail‐like abdomen, ventrally provided with pillow‐like subterminal pygopods possibly involved in locomotion.