The larval morphology of a new mid-Cretaceous stonefly and its systematic position in Plecoptera

Abstract

The larval stage is an essential part of the life history of stoneflies and can provide substantial biological and evolutionary information. However, well-preserved fossils of larvae are sparse. Herein, the larval morphology of a new extinct stonefly, Kachinoperla zwickigen. et sp. nov., is described based on its exuvia in mid-Cretaceous Kachin amber from northern Myanmar (98.79±0.62 Ma). The new stonefly also represents a new family, Kachinoperlidaefam. nov. according to its unique characters. Kachinoperlidae can be distinguished from other stonefly families by the following larval characters: predaceous mouthparts, subequal glossae and paraglossae, subequal maxillary and labial palps, reduced apical maxillary palpomere, trapezoidal pronotum, banded and semicircular wing pads, invisible notal contour, absent thoracic gills, shortest first two tarsomeres, and strongly projected abdominal tergum 10. The morphological comparison and phylogenetic analysis suggested the new family as a basal lineage within Systellognatha. Evolutionary implications implied by the larval characters are also discussed.