Comparative Wing Morphology Uncovers a New Mayfly Family (Insecta: Ephemeroptera) from Cretaceous Kachin Amber

The Mesozoic era, particularly the Cretaceous period, represents a critical chapter in the evolutionary history of mayflies (Insecta: Ephemeroptera), with numerous extinct lineages recorded from compression fossils and amber inclusions. Despite their basal position and structural diversity, the true extent of siphlonuroid diversity during this time remains underappreciated. Here, we describe a new mayfly genus and species, Venusdemilo venusae gen. et sp. nov., based on a female specimen in mid-Cretaceous Kachin amber (~99 Ma). The new taxon exhibits a suite of unique wing venation features, including a strongly developed cubital field with four bifurcate veins arising directly from CuA, an angled forewing tornus, absence of a basal arch in MP2, and the presence of attaching veinlets to AA distally. Comparative analysis excludes V. venusae gen. et sp. nov. from any existing family and supports the establishment of a new family, Venusdemiloidae fam. nov., to accommodate this distinctive taxon. The discovery reveals a previously undocumented morphological disparity within mid-Cretaceous Siphlonuroidea and underscores the underestimated diversity of fossil mayflies during the Mesozoic.