Asymmetrical rates of cladogenesis and extinction abound in the Tree of Life, resulting in numerous minute clades that are dwarfed by larger sister groups. Such taxa are commonly regarded as phylogenetic relicts or “living fossils” when they exhibit an ancient first appearance in the fossil record and prolonged external morphological stasis, particularly in comparison to their more diversified sister groups. Due to their special status, various phylogenetic relicts tend to be well-studied and prioritized for conservation. A notable exception to this trend is found within Amblypygi (“whip spiders”), a visually striking order of functionally hexapodous arachnids that are notable for their antenniform first walking leg pair (the eponymous “whips”). Paleoamblypygi, the putative sister group to the remaining Amblypygi, is known from Late Carboniferous and Eocene deposits, but is survived by a single living species, Paracharon caecus Hansen, 1921, that was last collected in 1899. Due to the absence of genomic sequence-grade tissue for this vital taxon, there is no global molecular phylogeny for Amblypygi to date, nor a fossil-calibrated estimation of divergences within the group. Here, we report a previously unknown species of Paleoamblypygi from a cave site in Colombia. Capitalizing upon this discovery, we generated the first molecular phylogeny of Amblypygi, integrating ultraconserved element sequencing with legacy Sanger datasets and including described extant genera. To quantify the impact of sampling Paleoamblypygi on divergence time estimation, we performed in silico experiments with pruning of Paracharon. We demonstrate that the omission of relicts has a significant impact on the accuracy of node dating approaches that outweighs the impact of excluding ingroup fossils, which bears upon the ancestral range reconstruction for the group. Our results underscore the imperative for biodiversity discovery efforts in elucidating the phylogenetic relationships of “dark taxa”, and especially phylogenetic relicts in tropical and subtropical habitats. The lack of reciprocal monophyly for Charontidae and Charinidae leads us to subsume them into one family, Charontidae, new synonymy.

中文翻译：

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遗迹的重新发现揭开了鞭蜘蛛（Amblypygi）的第一个全球系统发育史


生命之树中分支发生和灭绝的不对称率比比皆是，导致许多微小的分支与较大的姐妹群体相比显得相形见绌。当此类类群在化石记录中首次出现古老且长期外部形态停滞时，特别是与其更加多样化的姐妹类群相比，通常被视为系统发育遗迹或“活化石”。由于其特殊地位，各种系统发育遗迹往往会得到充分研究并优先保护。这一趋势的一个显着例外是 Amblypygi（“鞭蜘蛛”），这是一种视觉上引人注目的功能性六足蜘蛛纲动物，以其触角状的第一对步行腿（同名“鞭子”）而闻名。古鳗鱼（Paleoamblypygi）是剩下的钝鳗鱼（Amblypygi）的假定姊妹类群，在石炭纪晚期和始新世沉积物中被发现，但仅存有一个现存物种，即 Paracharon caecus Hansen，1921 年，最后一次收集于 1899 年。由于缺乏基因组序列 -尽管对这一重要分类群的组织进行了分级，但迄今为止，还没有 Amblypygi 的全球分子系统发育，也没有对该组内差异进行化石校准的估计。在这里，我们报告了来自哥伦比亚一个洞穴遗址的一种以前未知的古蜥蜴物种。利用这一发现，我们生成了第一个 Amblypygi 分子系统发育图，将超保守元件测序与遗留的桑格数据集相结合，并包括所描述的现存属。为了量化 Paleoamblypygi 采样对分歧时间估计的影响，我们在计算机模拟实验中进行了 Paracharon 的修剪。 我们证明，遗骸的遗漏对节点测年方法的准确性具有显着影响，其影响超过了排除群内化石的影响，而排除群内化石则影响该群的祖先范围重建。我们的结果强调了生物多样性发现努力阐明“暗类群”的系统发育关系的必要性，特别是热带和亚热带栖息地的系统发育遗迹。 Charontidae 和 Charinidae 缺乏互惠的单系性，导致我们将它们归入一个科，Charontidae，新的同义词。