Maximum recorded size of recent and fossil brachiopods

Changes in predator-prey interactions are often implicated as drivers of major evolutionary change. A prominent example is the dramatic changes in shallow marine assemblages during the Mesozoic Marine Revolution (MMR) when major clades, including rhynchonelliform brachiopods, became restricted and less diverse. Currently, shallow water temperate and polar brachiopods can be large, but in the tropics, they are all small. By contrast, we demonstrate that throughout the Jurassic large brachiopods occurred in shallow sites, from polar to tropical latitudes, but are absent in later periods from tropical areas. These changes occurred in parallel in both major orders (Rhynchonellida and Terebratulida) and also independently within the two sub-ordinal lineages within the Terebratulida (terebratulinids and terebratellinids). Increases in both grazing and predation pressures associated with the MMR might account for this pattern. However, we note that many current environments support both large brachiopods and high densities of grazing species and suggest that the pattern fits more closely to the intensification of durophagous predation in shallow tropical waters.捕食者-猎物相互作用的改变常被视作重大演化变革的驱动因素。其中一个典型案例便是中生代海洋革命（Mesozoic Marine Revolution, MMR）期间浅海生物组合发生的剧烈变化：包括有铰腕足类（rhynchonelliform brachiopods）在内的主要演化支类群，其分布范围大幅收缩、多样性显著降低。目前，温带与极地浅水环境中的腕足动物个体可长得较大，但热带海域的腕足动物个体均偏小。与之形成鲜明对比的是，本研究证实，整个侏罗纪时期，从极地到热带纬度的浅海生境中均存在大型腕足动物，但在侏罗纪之后的热带海域中再无大型腕足动物的踪迹。这一演化格局的变化在两大目——正形贝目（Rhynchonellida）与穿孔贝目（Terebratulida）——中均平行出现，且在穿孔贝目下的两个亚目支系（terebratulinids与terebratellinids）中也独立发生。与中生代海洋革命相关的牧食压力与捕食压力的增强，或许可以解释这一格局。但我们注意到，诸多现存环境中同时存在大型腕足动物与高密度的牧食生物类群，因此该演化格局更契合浅海热带水域中碎壳捕食（durophagous predation）作用增强的假说。