Data from: A Silurian short-great-appendage arthropod

A new arthropod, Enalikter aphson gen. et sp. nov., is described from the Silurian (Wenlock Series) Herefordshire Lagerstätte of the UK. It belongs to the Megacheira (=short-great-appendage group), which is recognized here, for the first time, in strata younger than mid-Cambrian age. Discovery of this new Silurian taxon allows us to identify a Devonian megacheiran representative, Bundenbachiellus giganteus from the Hunsrück Slate of Germany. The phylogenetic position of megacheirans is controversial: they have been interpreted as stem chelicerates, or stem euarthropods, but when Enalikter and Bundenbachiellus are added to the most comprehensive morphological database available, a stem euarthropod position is supported. Enalikter represents the only fully three-dimensionally preserved stem-group euarthropod, it falls in the sister clade to the crown-group euarthropods, and it provides new insights surrounding the origin and early evolution of the euarthropods. Recognition of Enalikter and Bundenbachiellus as megacheirans indicates that this major arthropod group survived for nearly 100 Myr beyond the mid-Cambrian.本文记述了产自英国志留纪温洛克统（Wenlock Series）赫里福德特异埋藏化石库（Herefordshire Lagerstätte）的全新节肢动物（arthropod）——Enalikter aphson gen. et sp. nov.（新属新种）。该类群隶属于大附肢类（Megacheira，亦称短巨附肢类short-great-appendage group），本研究首次在中寒武世之后的地层中确认了该类群的存在。这件志留纪新类群的发现，使得我们能够明确泥盆纪大附肢类代表物种——产自德国洪斯吕克板岩（Hunsrück Slate）的Bundenbachiellus giganteus的分类归属。大附肢类的系统发育位置长期存在争议：此前学界曾将其解读为螯肢动物干群（stem chelicerates）或真节肢动物干群（stem euarthropods）；但当将Enalikter与Bundenbachiellus纳入目前最全面的形态学数据库进行分析后，结果支持大附肢类属于真节肢动物干群的系统发育位置。Enalikter是目前唯一一件完全三维立体保存的真节肢动物干群化石，它处于冠群真节肢动物（crown-group euarthropods）的姊妹演化支中，为真节肢动物的起源与早期演化研究提供了全新的认知视角。将Enalikter与Bundenbachiellus归为大附肢类，表明这一重要的节肢动物类群在中寒武世之后仍存续了近1亿年。