Ovipositor and mouthparts in a fossil insect support a novel ecological role for early orthopterans in 300 million years old forests

A high portion of the earliest known, Pennsylvanian, insect fauna is composed of the so-called ‘lobeattid insects’, which systematic affinities and role as foliage feeders remain debated. We investigated hundreds of samples of a new lobeattid species from the Xiaheyan locality using a combination of photographic techniques, including Reflectance Transforming Imaging, and geometric morphometrics, to document its morphology, and infer its phylogenetic position and ecological role. Ctenoptilus frequens sp. nov. possessed a sword-shaped ovipositor whose valves interlocked by two ball-and-socket mechanisms. This unambiguously supports lobeattids as stem-relatives of all living Orthoptera (crickets, grasshoppers, katydids). Given the herein presented and other remains, it follows that this group experienced an early diversification coupled with high numbers of individuals. The ovipositor shape additionally indicates that ground was the preferred substrate for eggs. Visible mouthparts made it possible to assess the efficiency of the mandibular food uptake system in comparison to a wide array of extant species. The new species was omnivorous which explains the paucity of external damage on contemporaneous plant foliage.