Redefining the Thripida (Insecta: Paraneoptera)
The Thysanoptera (Paraneoptera) constitute a very diverse order of minute insects, characterized mainly by a ‘punch-and-suck’ mode of feeding due to a specialized asymmetrical gnathal apparatus with two maxillary stylets plus only one functional mandible. We have studied their fossil relatives from the Thripida family sensu Vishniakova (1981) and Zherikhin (2002), as revised by Nel et al. (2012a), in order to identify new morphological characters and help to polarize some of the characters present in the Thysanoptera. Here we present perfectly preserved specimens from the Middle Jurassic Daohugou beds of China, approximately 165 million years old, belonging to three new species and one new genus of Lophioneurida (Thripida): Lophiosina lini gen. et sp. nov., Undacypha bournieri sp. nov. and Undacypha kreiteri sp. nov. Precise analysis of the fossil heads revealed two ancestral mandibular sclerites that can still be found modified in the Recent thrips mouthcone, although in different ways in the two suborders of Thysanoptera, Terebrantia and Tubulifera. Their absence from the left side of the mouthcone of Terebrantia is a morphological apomorphy for this suborder. Studying fossils also allows us to inform the evolution of Thysanoptera in the deep past. Here we show that some of the characters usually thought to be apomorphies for Thysanoptera are instead apomorphies for all Thripida; this is the case for the typical gnathal apparatus but also for the eversible arolium and the fringe hairs. This leads us to redefine the Thysanoptera within the Thripida.