State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environments and Department of Geology, Northwest University, Xi'an 710069, China; Department of Earth Sciences, Palaeobiology, Uppsala University, Uppsala 75236, Sweden.
State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environments and Department of Geology, Northwest University, Xi'an 710069, China; Department of Palaeontology, University of Vienna, Althanstrasse 14, Vienna 1090, Austria.
Curr Biol. 2023 Apr 24;33(8):1565-1572.e3. doi: 10.1016/j.cub.2023.02.038. Epub 2023 Mar 8.
Morphology usually serves as an effective proxy for functional ecology, and evaluating morphological, anatomical, and ecological changes permits a deeper understanding of the nature of diversification and macroevolution. Lingulid (order Lingulida) brachiopods are both diverse and abundant during the early Palaeozoic but decrease in diversity over time, with only a few genera of linguloids and discinoids present in modern marine ecosystems, resulting in them frequently being referred to as "living fossils." The dynamics that drove this decline remain uncertain, and it has not been determined if there is an associated decline in morphological and ecological diversity. Here, we apply geometric morphometrics to reconstruct global morphospace occupation for lingulid brachiopods through the Phanerozoic, with results showing that maximum morphospace occupation was reached by the Early Ordovician. At this time of peak diversity, linguloids with a sub-rectangular shell shape already possessed several evolutionary features, such as the rearrangement of mantle canals and reduction of the pseudointerarea, common to all modern infaunal forms. The end Ordovician mass extinction has a differential effect on linguloids, disproportionally wiping out those forms with a rounded shell shape, while forms with sub-rectangular shells survived both the end Ordovician and the Permian-Triassic mass extinctions, leaving a fauna predominantly composed of infaunal forms. For discinoids, both morphospace occupation and epibenthic life strategies remain consistent through the Phanerozoic. Morphospace occupation over time, when considered using anatomical and ecological analyses, suggests that the limited morphological and ecological diversity of modern lingulid brachiopods reflects evolutionary contingency rather than deterministic processes.
形态通常是功能生态学的有效替代指标，评估形态、解剖和生态变化可以更深入地了解多样化和宏观进化的本质。早古生代的舌形贝（Lingulida 目）腕足动物种类繁多，数量丰富，但随着时间的推移，其多样性逐渐减少，现代海洋生态系统中只有少数几个舌形贝属和瓣鳃贝属存在，因此它们经常被称为“活化石”。导致这种下降的动态仍然不确定，也不确定是否存在形态和生态多样性的相关下降。在这里，我们通过应用几何形态测量学来重建舌形贝腕足动物在整个显生宙的全球形态空间占据情况，结果表明，早奥陶世达到了最大形态空间占据。在这个多样性达到顶峰的时期，具有矩形壳形状的舌形贝已经拥有了几个进化特征，例如外套腔管的重新排列和伪间区的减少，这些特征在所有现代底栖形式中都很常见。奥陶纪末大灭绝对舌形贝有不同的影响，不成比例地消灭了那些具有圆形壳形状的形式，而具有矩形壳形状的形式在奥陶纪末和二叠纪-三叠纪大灭绝中都存活了下来，留下的动物群主要由底栖形式组成。对于瓣鳃贝，其形态空间占据和表栖生活策略在整个显生宙都保持一致。随着时间的推移，考虑到解剖学和生态学分析，形态空间占据表明现代舌形贝腕足动物有限的形态和生态多样性反映了进化的偶然性，而不是确定性过程。
