Lycopsid–arthropod associations and odonatopteran oviposition on Triassic herbaceous Isoetites

Associations between lycopsid and herbivorous arthropods are rare in the fossil record and equally sparse among the three surviving lineages of Lycopodiaceae, Selaginellaceae and Isoëtaceae. However, from the Middle–Upper Triassic Madygen Formation of southwestern Kyrgyzstan, we describe the first association between an isoetalean host, Isoetites (a quillwort), and a pattern of elliptical egg insertion scars that altered the hostʹs live plant tissues. This ovipositional damage, in some cases deployed in a stereotypical zigzag pattern, was most likely caused by small damselfly-like insects from the extinct suborder Archizygoptera of the order Odonatoptera (dragonflies). If this identification is correct, it indicates considerable behavioral stasis of dragonflies extending deep into the Mesozoic. Our detection of lycopsid ovipositional damage adds to the list of major plant hosts from the preangiospermous Mesozoic that were resources for host use by egg-laying dragonflies, particularly horsetails, ferns, and seed plants that included conifers, peltasperms, corystosperms, ginkgophytes, bennettitaleans and probably cycads.