'Fish' (Actinopterygii and Elasmobranchii) diversification patterns through deep time.

Area of Science:

• Paleontology
• Evolutionary Biology
• Ichthyology

Background:

• Ray-finned fishes and sharks comprise over half of vertebrate diversity but their evolutionary history is poorly understood.
• Previous studies treated these groups separately due to differing fossil records and sampling biases.
• Direct analysis of fossil data is prone to biases, necessitating analytical correction for accurate palaeodiversity assessment.

Purpose of the Study:

• To conduct a comprehensive analysis of fish evolutionary history by comparing phylogenies and fossil records for Actinopterygii and Elasmobranchii.
• To correct for biases in the fossil record and reveal deep-time palaeodiversity signals and diversification events.
• To qualitatively and quantitatively assess palaeodiversity events within their palaeoenvironmental and biological contexts.

Main Methods:

• Comparative analysis of large datasets including recent and fossil taxa phylogenies.
• Examination of fossil records for Actinopterygii and Elasmobranchii throughout the Mesozoic-Cainozoic interval.
• Bias correction methods applied to palaeodiversity curves to reconstruct evolutionary signals.

Main Results:

• Elasmobranchii possess a superior fossil record quality compared to Actinopterygii, particularly due to microfossil preservation and limited freshwater diversity.
• Identified significant diversification events for elasmobranchs, marine and freshwater actinopterygians in the Jurassic, Cretaceous, and Paleocene-Eocene.
• The Cenomanian and Paleocene-Eocene intervals represent exceptional radiation events for all fish groups.

Conclusions:

• Fish evolutionary history is shaped by both biotic and abiotic factors, including palaeotemperatures, sea-levels, and environmental heterogeneity.
• Understanding fish diversification requires correcting for fossil record biases and considering group-specific preservation potentials.
• The study provides a corrected deep-time phylogenetic palaeodiversity signal for ray-finned fishes and sharks, highlighting major evolutionary radiations.