Metamorphosis is ancestral for crown euarthropods, and evolved in the Cambrian or earlier

Macroevolutionary developmental biology employs fossilized ontogenetic data and phylogenetic comparative methods to probe the evolution of development at ancient nodes. Despite the prevalence of ecologically differentiated larval forms in marine invertebrates, it has been frequently presumed that the ancestors of arthropods were direct developers, and that metamorphosis may not have evolved until the Ordovician or later. Using fossils and new dated phylogenies, I infer that metamorphosis was likely ancestral for crown arthropods, contradicting this assumption. Based on a published morphological dataset encompassing 217 exceptionally preserved fossil and 96 extant taxa, fossils were directly incorporated into both the topology and age estimates, as in “tip dating” analyses. Using data from post-embryonic fossils representing 25 species throughout stem and crown arthropod lineages (as well as most of the 96 extant taxa), characters for metamorphosis were assigned based on inferred ecologi...

宏观演化发育生物学（Macroevolutionary developmental biology）采用化石保存的个体发育数据（ontogenetic data）与系统发育比较方法（phylogenetic comparative methods），探究古老演化节点处的发育演化历程。尽管海洋无脊椎动物中广泛存在生态分化的幼虫形态，但学界此前普遍认为节肢动物的祖先为直接发育类群，且变态发育直至奥陶纪乃至更晚才得以演化产生。本研究借助化石与全新的定年系统发育树，推断变态发育很可能是冠群节肢动物（crown arthropods）的祖征，这与前述学界假定相悖。本研究基于一项已发表的形态学数据集，该数据集涵盖217件保存异常完好的化石标本与96个现生类群（extant taxa），且如"末端定年（tip dating）"分析一般，将化石直接纳入系统发育拓扑结构与年代估算环节。本研究利用涵盖茎群节肢动物（stem arthropods）与冠群节肢动物（crown arthropods）演化支共25个物种的胚后发育化石（post-embryonic fossils）数据（同时纳入96个现生类群中的绝大多数类群），对变态发育相关性状的赋值基于推测的生态学[原文内容未完整呈现]。