The first orthopteran fossils from the Lower Cretaceous (Albian) Jinju Formation of Korea: Ethological implications for elcanids

Abstract

The lower Albian Jinju Formation has produced various fossils of invertebrates. Of them, insect fossils have remained understudied, and especially, orthopteran fossils have never been described from the Jinju Formation. Here we report a new species of the Elcanidae (Orthoptera: Elcanoidea), Panorpidium spica sp. nov. based on three specimens from the Jinju Formation. Notably, we have applied Wavelength Dispersive Spectrometer (WDS) analysis for the first time on insect fossils, and discovered that the carbon elemental maps are helpful in recognizing crucial morphology. The presence of pterostigmata in forewing supports that elcanids evolved a unique flight mechanism distinct from other extant orthopterans. Based on a detailed morphological comparison with the paddles of the extant tridactylids, it is inferred that the leaf-shaped spurs on the metatibiae of elcanids were used for jumping on the water, although other possible functions cannot be ruled out. Diving into the water and jumping on the water surface must have been an effective way of escaping from predators, both for the flightless nymphs and the short-range flying adults.