A split-footed lacewing larva from about 100-million-year-old amber indicates a now extinct hunting strategy for neuropterans

In larvae of lacewings (Neuroptera), each mandible is conjoined with its corresponding maxilla (upper and lower jaws) forming a stylet. Stylets are specialized for piercing, liquefying and sucking the tissues of their prey. The shape, length and thickness of the stylets can differ immensely among larvae of different in-groups of Neuroptera. In addition, the stylets may possess a single tooth or multiple teeth of various sizes and positions, or may totally lack teeth. The larvae of split-footed lacewings (Nymphidae) are often characterized by a single tooth on each stylet and a relatively wide head capsule. The tooth in known larvae is arranged in the plane of movement of the stylet itself, as also often seen in other lacewing larvae. Here we describe and analyse a new type of fossil representatives of Nymphidae from about 100-million-year-old Kachin Myanmar amber. The new fossil type has a special morphology with prominent lateral processes on the head capsule and a single prominent tooth per stylet. The fossil type differs from all the other known larvae of Nymphidae by the arrangement of the tooth: it extends outside of the plane of movement of the stylets. Similar arrangements of teeth or spines outside of the plane of movement also occur in some raptorial appendages of other representatives of Euarthropoda, where they form a grasping basket. We discuss the implications of this unusual fossil type, concerning its functional morphology and ecology. •