Non‐calcified marine macroalgae (“seaweeds”) play a variety of key roles in the modern Earth system, and it is likely that they were also important players in the geological past, particularly during critical transitions such as the Cambrian Explosion (CE) and the Great Ordovician Biodiversification Event (GOBE). To investigate the morphology and ecology of seaweeds spanning the time frame from the CE through the GOBE, a carefully vetted database was constructed that includes taxonomic and morphometric information for non‐calcified macroalgae from 69 fossil deposits. Analysis of the database shows a pattern of seaweed history that can be explained in terms of two floras: the Cambrian Flora and the Ordovician Flora. The Cambrian Flora was dominated by rather simple morphogroups, whereas the Ordovician Flora, which replaced the Cambrian Flora in the Ordovician and extended through the Silurian, mainly comprised comparatively complex morphogroups. In addition to morphogroup representation, the two floras show marked differences in taxonomic composition, morphospace occupation, functional‐form group representation, and life habit, thereby pointing to significant morphological and ecological changes for seaweeds roughly concomitant with the GOBE and the transition from the Cambrian to Paleozoic Evolutionary Faunas. Macroalgal changes of a similar nature and magnitude, however, are not evident in concert with the CE, as the Cambrian Flora consists largely of forms established during the Ediacaran. The cause of such a lag in macroalgal morphological diversification remains unclear, but an intriguing possibility is that it signals a previously unknown difference between the CE and GOBE with regard to the introduction of novel grazing pressures. The consequences of the establishment of the Ordovician Flora for shallow marine ecosystems and Earth system dynamics remain to be explored in detail but could have been multifaceted and potentially include impacts on the global carbon cycle.

中文翻译：

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古生代早期动物多样化过程中的海藻形态和生态学：两个植物的故事。

非钙化海洋大型藻类（“海藻”）在现代地球系统中起着多种关键作用，而且它们很可能也是地质过去的重要参与者，尤其是在诸如寒武纪爆炸（CE）和奥陶纪生物多样性大事件（GOBE）。为了研究从CE到GOBE的时间跨度的海藻形态和生态学，构建了一个经过仔细审查的数据库，其中包括来自69个化石矿床的非钙化大型藻类的分类学和形态计量信息。对数据库的分析显示了海藻的历史模式，可以用两种植物群来解释：寒武纪植物群和奥陶纪植物群。寒武纪植物群以相当简单的形态群为主，而奥陶纪植物群，它取代了奥陶纪的寒武纪植物群，并延伸到志留纪，主要由相对复杂的形态群组成。除形态群表示外，这两个菌群在分类学组成，形态空间占用，功能形式群表示和生活习性上也显示出显着差异，从而指出海藻的显着形态和生态变化与GOBE和寒武纪过渡有关到古生代演化动物区系。然而，由于寒武纪植物区系主要由埃迪卡拉时期形成的形式组成，因此与CE一致的大型藻类变化与CE并不一致。大型藻类形态多样性出现这种滞后的原因尚不清楚，但是一个引人入胜的可能性是，它标志着CE和GOBE在引入新型放牧压力方面的先前未知的差异。建立奥陶纪植物区系对浅海生态系统和地球系统动力学的影响仍有待详细探讨，但可能是多方面的，并可能包括对全球碳循环的影响。