New fossil data and phylogenetic inferences shed light on the morphological disparity of Mesozoic Sinoalidae (Hemiptera, Cicadomorpha)

Like many fossil insect groups, the systematic framework of extinct Homoptera' is mainly based on venational traits of isolated wings; most taxa of Mesozoic Sinoalidae, however, were erected with whole-bodied specimens. On the basis of new fossil data and phylogenetic analyses, this froghopper family is herein chosen as a case study to discuss the potential influence of the absence and/or neglect of body information in palaeoentomological studies. Mesodorus orientalis Chen et Wang, gen. et sp. nov., found in the mid-Cretaceous Burmese amber, bears a venational topology of fore- and hindwings similar to that of the genus Fangyuania from the same horizon and locality, but distinctly differs from the latter and other known sinoalids in possessing a series of unique body characters. Given the similar wing features, Jiania crebra and J. gracila were proposed to be synonyms in a recent study; these two congeners, however, are apparently discernable in their ovipositor and so the synonym should be rejected. Three main clades were recovered within the Sinoalidae in our cladistic analyses, including Clade I (Stictocercopis + Chengdecercopis), Clade II (Huabeicercopis + Luanpingia + Sinoala + Jiania + Shufania), and Clade III (Fangyuania + Mesodorus), and their relationship is as following: Clade I + (Clade II+Clade III). The Jurassic Clade I, as the basal lineage, is remarkably different from other sinoalids in bearing wings with complex venation, but similar to the Jurassic Clade II in body structures. The Cretaceous Clade III possesses a reduced wing topology similar to Clade II, but differs from the latter in possessing a series of novel body characteristics for each taxon (i.e., Fangyuania and Mesodorus). Unsurprisingly, our finds confirm that the information from body structures, vital to understanding the biodiversity and evolutionary history of extinct insects, should not be ignored in palaeoentomological studies.