The rise of ray-finned fishes (Actinopterygii) after the fall of the Devonian world.

摘要

Ray-finned fishes (Actinopterygii) make up more than half of all living vertebrates, represented by around 30,000 species of all forms and functions. While living actinopterygians are used as model organisms and study groups in multiple fields of biology, their early evolutionary history and the mechanisms underlying their modern dominance are not well characterized. Investigation of the context and characteristics of the initial, Devonian-Mississippian (416-318 million years ago; Ma) diversification of ray-finned fishes is therefore essential for understanding the evolutionary and ecological underpinnings of the modern vertebrate fauna. Here, I combine approaches from quantitative paleobiology and community ecology with detailed re-examination of important early taxa in order to study patterns of divergence, disparity and diversity in Devonian-Mississippian actinopterygians.;I compiled a new diversity dataset for later Devonian (391-359 Ma) and Mississippian (359-318 Ma) jawed vertebrates in order to investigate the patterns of global diversity and their relationship with two major mass extinction intervals, the Frasnian-Famennian Kellwasser event (374 Ma) and the end-Devonian Hangenberg event (359 Ma). Site-specific species lists drawn from this larger dataset were subjected to analyses of faunal composition, revealing complete and sudden turnover of the global vertebrate fauna associated with the Hangenberg event. The Hangenberg event sets the stage for the diversification of actinopterygians: all Mississippian and modern aquatic faunas are dominated by ray-finned fishes.;The Tournaisian is marked by the first appearance of actinopterygian durophages (e.g. Fouldenia) and the founders of often widespread, long-lived Paleozoic groups that go on to contain the first deep-bodied and eel-like actinopterygians (e.g. Tarrasius) in the Visean (345-328 Ma). While it was once thought such divergent body plans arose only rarely among non-teleosts, re-investigation of relevant taxa shows that such morphologies and traits appeared in multiple lineages. The functional, ecological and morphological diversity of early ray-finned fishes might approximate the same in Mesozoic and later vertebrate biotas dominated by neopterygians and teleosts. Thus, the pre-requisites of modern actinopterygian dominance were achieved in the aftermath of the end-Devonian mass extinction, a major contingent event in subsequent vertebrate evolution.