Data from: Two pulses of morphological diversification in Pacific pelagic fishes following the Cretaceous–Palaeogene mass extinction

Molecular phylogenies suggest some major radiations of open-ocean fish clades occurred roughly coincident with the K/Pg boundary, however the timing and nature of this diversification is poorly constrained. Here we investigate evolutionary patterns in ray-finned fishes across the Cretaceous-Palaeogene (K/Pg) Mass Extinction 66 million years ago (Ma), using microfossils (isolated teeth) preserved in a South Pacific sediment core spanning 72-43 Ma. Our record does not show significant turnover of fish tooth morphotypes at the K/Pg boundary: only two of 48 Cretaceous tooth morphotypes disappear at the event in the South Pacific, a rate no different from background extinction. Capture-mark-recapture analysis finds two pulses of origination in fish tooth morphotypes following the mass extinction. The first pulse, at ~64 Ma, included short-lived teeth, as well as forms that contribute to an expansion into novel morphospace. A second pulse, centered at ~58 Ma, produced morphotype novelty in a different region of morphospace from the first pulse, and contributed significantly to Eocene tooth morphospace occupation. There was no significant increase in origination rates or expansion into novel morphospace during the early or middle Eocene, despite a near 10-fold increase in tooth abundance during that interval. Our results suggest that while the K/Pg event had a minor impact on fish diversity in terms of extinction, the removal of the few dominant Cretaceous morphotypes triggered a sequence of origination events allowing fishes to rapidly diversify morphologically, setting the stage for exceptional levels of ray-finned fish diversity in the Cenozoic.

分子系统发育（Molecular Phylogenies）研究显示，部分远洋鱼类支系的大辐射演化事件大致与白垩纪-古近纪（K/Pg）界线同期发生，但该辐射事件的发生时间与具体过程仍未得到严格约束。本研究依托采自南太平洋、涵盖7200万至4300万年前地层的沉积岩芯中保存的微体化石（孤立牙齿），对发生于6600万年前（Ma）的白垩纪-古近纪（K/Pg）集群灭绝事件前后的辐鳍鱼类（ray-finned fishes）演化模式展开研究。本研究的化石记录显示，K/Pg界线处并未出现鱼类牙齿形态型（tooth morphotypes）的显著类群更替：南太平洋剖面中，48种白垩纪牙齿形态型仅2种在该灭绝事件中消失，其灭绝速率与背景灭绝率并无显著差异。标记-重捕分析（Capture-mark-recapture analysis）结果显示，集群灭绝事件后，鱼类牙齿形态型出现两次起源脉冲。第一次脉冲发生于约6400万年前，包含短命型牙齿，以及推动物种开拓新形态空间（morphospace）的牙齿类型。第二次脉冲以约5800万年前为中心，在与第一次脉冲截然不同的形态空间区域产生了新的形态型，并显著提升了始新世（Eocene）鱼类牙齿的形态空间占据度。尽管始新世早中期的牙齿化石丰度增长了近10倍，但该时期的起源速率并未出现显著提升，也未出现向新形态空间的拓展。本研究结果表明，尽管K/Pg灭绝事件对鱼类多样性的灭绝影响较为微弱，但少数占主导地位的白垩纪牙齿形态型的消失，触发了一系列起源事件，使得鱼类得以快速实现形态多样性分化，为新生代（Cenozoic）辐鳍鱼类多样性的空前繁荣奠定了基础。