Morphological diversity of dragonfly and damselfly larvae over the last 300 million years

The larvae of dragonflies and damselflies (Odonatoptera) exhibit great morphological diversity, underpinning their important role as aquatic predators in freshwater ecosystems. Depending on species, odonatopteran larvae develop through 10–15 moults, with the metamorphosis to a flying adult taking place in the last moult, so they spend most of their lifetime under water. This pattern of aquatic larvae and flying terrestrial adults is generally referred to as “merolimic”. Their highly prominent compound eyes as well as the specialised extendable mouthparts (“labial mask”), which can be moved forward rapidly, enable the larvae to efficiently capture prey. Prey items include small crustaceans, other merolimnic larvae, but also tadpoles and small fishes. Fossil finds of odonatopterans, including a possible larva, reach back into the Carboniferous, over 300 million years ago. We here report new finds of odontopteran larvae from a more unusual type of preservation, amber. Amber less often preserves aquatic specimens, making odonatopteran larvae in amber rather rare. The new fossil comes from about 100 million years old Kachin amber. So far, less than a handful of odonatoperan larvae have been reported from this deposit, hence expanding the known diversity of these larvae. This includes also larvae with rather slender labial masks. We compared the shapes of the labial masks within a quantitative frame to reconstruct the evolutionary changes of this structure.