Fossil insects of the Middle Triassic Gayndah Formation of south-eastern Queensland

Abstract

The Middle Triassic (Anisian) Gayndah Formation is the northernmost unit of the Early–Middle Triassic Esk Basin of south-eastern Queensland. Fossil insects were discovered in the formation in 1962 and 90 specimens have been collected since then. Of those, the 80 specimens identifiable to Order level are mainly Hemiptera (39%) and Coleoptera (36%), with much fewer Odonata s.l., Plecoptera, Neuroptera, Mecoptera and Trichoptera, and single specimens of Blattodea, Reculida, Titanoptera and ? Orthoptera. The dominance of Hemiptera and Coleoptera is likely due to the durability of their tegmina and elytra during sedimentary transport and deposition, rather than an indication of faunal composition. Faunal elements identified to family or lower level are: Reculida: Shurabia australis Rasnitsyn, 1982 (Geinitziidae); Plecoptera: ? Gondwanoperlidium spp. (Euxenoperlidae); Hemiptera: Tennentsia evansi Lambkin, 2015, Dysmorphoptiloides ellisi Lambkin, 2015, Mesonirvana dougsmithi sp. nov. (Dysmorphoptilidae), Mesoscytina woodsi Lambkin, 2016 (Scytinopteridae), Hylicellidae; Neuroptera: Riekchotes reticulatus gen. et sp. nov. (Ithonidae), Lithosmylidia baronne Lambkin, 1988, Lithosmylidia sp. (Archeosmylidae), Gayndahpsychops carsburgi Lambkin, 2014 (Osmylopsychopidae); Mecoptera: Mesoses gayndah Lambkin, 2014 (Mesopsychidae), Mesochorista sp. (Permochoristidae); Trichoptera: Prorhyacophila colliveri Riek, 1955 (Prorhyacophilidae). The fauna is a typical Triassic transitional one that has commonalities with the more extensively sampled and species-rich faunas of the Queensland Late Triassic insect localities at Denmark Hill, Dinmore and Mount Crosby. Exceptions are a hindwing base ascribed to the Titanoptera, an order known in Australia only from the Middle Triassic Hawkesbury Sandstone of New South Wales, and the forewing of Riekchotes reticulatus, the earliest and only Triassic record of the neuropteran family Ithonidae.