英国伦敦帝国理工学院Sutton Mark D团队最新的研究报道了志留纪新刺虫化石，揭示了软体动物复杂的早期历史。这一研究成果于2025年1月8日发表在国际顶尖学术期刊《自然》上。

软体动物门是物种数量第二丰富的动物门，但早期软体动物的进化途径一直存在争议。这个高度多样化和长寿的动物群现在只保留了过去形式的一小部分。最近的分析一致发现，它基本可分为两个姊妹分支，Conchifera（包括腹足类、双壳类和头足类）和Aculifera，包括Polyplacophora（“石鳖”）和Aplacophora。

软体动物的进化总体上以身体平面特征的可塑性为特征，但从历史上看，aculiferans被认为进化更为保守。来自古生代早期少数完整保存的aculiferan或类aculiferan化石被认为是其过渡形式，提出了现有多placophoran和aplacophoran身体形态之间的特征极性问题。早期aculiferans的历史，以及它们所占据的形态和生态范围，仍然没有得到充分的采样。

研究人员描述了来自志留纪Herefordshire特异埋藏的两种新的三维保存的aculiferan物种，这大大扩展了进化支系的形态和生态范围。系统发育分析提示了在一个复杂的类群关系中的位置，显示基本特征状态会发生逆转，如瓣膜的存在和脚的性质。与先前的形态保守性假设相反，早期aculiferans的进化产生了大量不寻常的形式，与其他冠类软体动物的多样化相当。

附：英文原文

Title: New Silurian aculiferan fossils reveal complex early history of Mollusca

Author: Sutton, Mark D., Sigwart, Julia D., Briggs, Derek E. G., Gueriau, Pierre, King, Andrew, Siveter, David J., Siveter, Derek J.

Issue&Volume: 2025-01-08

Abstract: Mollusca is the second most species-rich animal phylum, but the pathways of early molluscan evolution have long been controversial. Modern faunas retain only a fraction of the past forms in this hyperdiverse and long-lived group. Recent analyses have consistently recovered a fundamental split into two sister clades, Conchifera (including gastropods, bivalves and cephalopods) and Aculifera, comprising Polyplacophora (‘chitons’) and Aplacophora. Molluscan evolution in toto is characterized by plasticity in body-plan characters, but historically aculiferans have been interpreted as more conservative. The few completely preserved aculiferan or aculiferan-like fossils from the early Palaeozoic have been largely regarded as transitional forms that inform questions of character polarity between the extant polyplacophoran and aplacophoran body forms. The history of early aculiferans, and the morphological and ecological range that they occupied, remain inadequately sampled. Here we describe two new three-dimensionally preserved aculiferan species from the Silurian Herefordshire Lagersttte. which substantially extend the morphological and ecological range of the clade. Phylogenetic analyses indicate positions within a complex nexus of taxa and suggest reversals in the states of fundamental characters such as the presence of valves and the nature of the foot. In contrast to previous hypotheses of morphological conservatism, evolution in early aculiferans generated a profusion of unusual forms comparable to the diversification of other crown-group molluscs.

DOI: 10.1038/s41586-024-08312-0

Source: https://www.nature.com/articles/s41586-024-08312-0