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.

中文翻译：

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白垩纪缅甸琥珀中的观赏羽毛：解开以轴为主的羽毛结构之谜

在过去的 20 年里，恐龙周围羽毛的压缩化石极大地扩展了我们对羽毛起源和进化的理解。迄今为止发现的最奇特的羽毛形态类型之一是轴支配羽毛 (RDF)，也被称为近端带状羽状羽毛 (PRPF)。这些细长的羽毛仅在尾羽中发现，通常成对出现，同时具有流光（不是近端带状）和球拍羽形态。在这里，我们描述了来自上白垩纪缅甸琥珀（~ 99 Ma）的大量孤立和配对 RDF 样本集。琥珀在三个维度上保留了这些脆弱结构的最精细细节，表明 RDF 形成了独特的羽毛形态，具有腹侧开放的羽轴，