Data from: Extant primitively segmented spiders have recently diversified from an ancient lineage

Living fossils are lineages that have retained plesiomorphic traits through long time periods. It is expected that such lineages have both originated and diversified long ago. Such expectations have recently been challenged in some textbook examples of living fossils, notably in extant cycads and coelacanths. Using a phylogenetic approach, we tested the patterns of the origin and diversification of liphistiid spiders, a clade of spiders considered to be living fossils due to their retention of arachnid plesiomorphies and their exclusive grouping in Mesothelae, an ancient clade sister to all modern spiders. Facilitated by original sampling throughout their Asian range, we here provide the phylogenetic framework necessary for reconstructing liphistiid biogeographic history. All phylogenetic analyses support the monophyly of Liphistiidae and of eight genera. As the fossil evidence supports a Carboniferous Euramerican origin of Mesothelae, our dating analyses postulate a long eastward over-land dispersal towards the Asian origin of Liphistiidae during the Palaeogene (39–58 Ma). Contrary to expectations, diversification within extant liphistiid genera is relatively recent, in the Neogene and Late Palaeogene (4–24 Ma). While no over-water dispersal events are needed to explain their evolutionary history, the history of liphistiid spiders has the potential to play prominently in vicariant biogeographic studies.

活化石（living fossils）是指在漫长地质时段中保留祖征（plesiomorphic traits）的演化支系。学界此前普遍认为，此类演化支系的起源与分化均发生在遥远的地质年代。但近期针对若干教科书级经典活化石类群的研究对这一认知提出了质疑，其中以现生苏铁（cycads）和腔棘鱼（coelacanths）最为突出。本研究采用系统发育分析方法（phylogenetic approach），对地蛛科（Liphistiidae）蜘蛛的起源与分化模式进行了检验。该类群因保留了蛛形纲祖征（arachnid plesiomorphies），且隶属于与所有现生蜘蛛互为姐妹群的古老单系群——中纺亚目（Mesothelae），而被视作活化石类群。依托在其整个亚洲分布范围内开展的原创性采样，我们构建了重建地蛛科生物地理历史所需的系统发育框架。所有系统发育分析结果均支持地蛛科及其下辖8个属的单系性。鉴于化石证据表明中纺亚目起源于石炭纪（Carboniferous）的欧美大陆，我们的测年分析推测，地蛛科于古近纪（Palaeogene，39~58 Ma）期间通过长期的陆地东向扩散抵达亚洲并完成起源。与此前的学界预期相悖，现生地蛛科各属的分化时间相对较晚，集中在新近纪（Neogene）与古近纪晚期（Late Palaeogene，4~24 Ma）。尽管无需借助跨水扩散事件即可解释地蛛科的演化历程，但其演化历史仍有望在分替生物地理学（vicariant biogeographic）研究中占据重要地位。