School of Geography, Geology and the Environment, University of Leicester, Leicester LE1 7RH, UK.
Faculty of Advanced Science and Technology, Kumamoto University, Kumamoto, 860-8555, Japan.
Biol Lett. 2021 Dec;17(12):20210403. doi: 10.1098/rsbl.2021.0403. Epub 2021 Dec 1.
The fossil record of terrestrialization documents notable shifts in the environmental and physiological tolerances of many animal and plant groups. However, for certain significant components of modern freshwater and terrestrial environments, the transition out of marine settings remains largely unconstrained. Ostracod crustaceans occupy an exceptional range of modern aquatic environments and are invaluable palaeoenvironmental indicators in the fossil record. However, pre-Carboniferous records of supposed non-marine and marginal marine ostracods are sparse, and the timing of their marine to non-marine transition has proven elusive. Here, we reassess the early environmental history of ostracods in light of new assemblages from the late Silurian of Vietnam. Two, low diversity but distinct ostracod assemblages are associated with estuarine deposits. This occurrence is consistent with previous incidental reports of ostracods occupying marginal and brackish settings through the late Silurian and Devonian. Therefore, ostracods were pioneering the occupation of marginal marine and estuarine settings 60 Myr before the Carboniferous and they were a component of the early phase of transition from marine to non-marine environments.
陆生化的化石记录记录了许多动植物群体在环境和生理耐受性方面的显著变化。然而，对于现代淡水和陆地环境的某些重要组成部分，从海洋环境过渡的情况在很大程度上仍未得到限制。介形类甲壳动物占据了现代水生环境的特殊范围，并且是化石记录中非常有价值的古环境指示物。然而，前石炭纪时期所谓的非海相和边缘海相介形类的记录却很少，它们从海洋到非海洋的过渡时间也一直难以确定。在这里，我们根据越南晚志留世的新组合重新评估了介形类动物的早期环境历史。两种低多样性但明显不同的介形类动物组合与河口沉积物有关。这种情况与以前通过晚志留世和泥盆纪偶然报道的介形类动物占据边缘和半咸水环境的情况是一致的。因此，介形类动物在石炭纪前 6000 万年就开始开拓边缘海和河口环境，它们是从海洋到非海洋环境过渡的早期阶段的一个组成部分。
