Over the last 20 years, compression fossils of feathers surrounding dinosaurs have greatly expanded our understanding of the origin and evolution of feathers. One of the most peculiar feather morphotypes discovered to date are rachis dominated feathers (RDFs), which have also been referred to as proximally ribbon-like pennaceous feathers (PRPFs). These elongate feathers are only found in the tail plumage, typically occurring in pairs with both streamer (not proximally ribbon-like) and racket-plume morphologies recognized. Here we describe a large sample set of isolated and paired RDFs from Upper Cretaceous Burmese amber (~99 Ma). Amber preserves the finest details of these fragile structures in three dimensions, demonstrating that RDFs form a distinct feather morphotype with a ventrally open rachis, and with significant variability in pigmentation, microstructure, and symmetry.

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International audienceTwo new genera and species of fossil chrysidoid wasps belonging to the families Chrysididae and Bethylidae are described from Charentese (Fouras Bois-Vert and Archingeay) lower Upper Cretaceous amber of France. New taxa include: Sphaerocleptes neraudeaui n. gen. et sp., and Nucifrangibulum carentonensis n. gen. et sp. A new bethylid wasp is also described but left in open nomenclature. These findings are the first records of the subfamilies Cleptinae and Bethylinae in these deposits and time interval. The implications of these discoveries, and the features shared with previously known taxa are discussed