Quantifying morphological evolution is key to determining the patterns and processes underlying the origin of phyla. We constructed a hierarchical morphological character matrix to characterize the radiation and establishment of echinoderm body plans during the early Paleozoic. This showed that subphylum-level clades diverged gradually through the Cambrian, and the distinctiveness of the resulting body plans was amplified by the extinction of transitional forms and obscured by convergent evolution during the Ordovician. Higher-order characters that define these body plans were not fixed at the origin of the phylum, countering hypotheses regarding developmental processes governing the early evolution of animals. Instead, these burdened characters were flexible, enabling continued evolutionary innovation throughout the clades' history.

中文翻译：

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一门起源的进化和发展。

量化形态进化是确定门起源的模式和过程的关键。我们构建了一个分层的形态特征矩阵来表征早期古生代棘皮动物身体计划的辐射和建立。这表明亚门级进化枝在寒武纪逐渐分化，由此产生的身体计划的独特性被过渡形态的灭绝放大，并被奥陶纪的趋同进化所掩盖。定义这些身体计划的高阶特征并没有固定在门的起源上，这与有关控制动物早期进化的发育过程的假设相反。相反，这些负担过重的角色是灵活的，能够在整个进化枝的历史中不断进行进化创新。