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New Age of Fishes initiated by the Cretaceous−Paleogene mass extinction

Citation

Sibert, Elizabeth C.; Norris, Richard D. (2020), New Age of Fishes initiated by the Cretaceous−Paleogene mass extinction, Dryad, Dataset, https://doi.org/10.5061/dryad.prr4xgxj4

Abstract

Ray-finned fishes (Actinopterygii) comprise nearly half of all modern vertebrate diversity, and are an ecologically and numerically dominant megafauna in most aquatic environments. Crown teleost fishes diversified relatively recently, during the Late Cretaceous and early Paleogene, although the exact timing and cause of their radiation and rise to ecological dominance is poorly constrained. Here we use microfossil teeth and shark dermal scales (ichthyoliths) preserved in deep-sea sediments to study the changes in the pelagic fish community in the latest Cretaceous and early Paleogene. We find that the Cretaceous−Paleogene (K/Pg) extinction event marked a profound change in the structure of ichthyolith communities around the globe: Whereas shark denticles outnumber ray-finned fish teeth in Cretaceous deep-sea sediments around the world, there is a dramatic increase in the proportion of ray-finned fish teeth to shark denticles in the Paleocene. There is also an increase in size and numerical abundance of ray-finned fish teeth at the boundary. These changes are sustained through at least the first 24 million years of the Cenozoic. This new fish community structure began at the K/Pg mass extinction, suggesting the extinction event played an important role in initiating the modern “age of fishes.”

Methods

Samples were processed using a standard ImageJ protocol to clean the images and find individual light "particles" on a dark background. Due to their often semi-transparent nature, often teeth had to be "filled in" to ensure that ImageJ found their correct borders. This was done iteratively and by hand, until all objects visible in the image were captured by the "Analyze Particles" function corretly.

Usage Notes

Open the 4th ("*_BW") image in ImageJ to see the particle IDs found using "Analyze Particles" protocol. For some reason, the outlines and numbers aren't readable by regular image viewers, but are saved in the image and will appear if opened with ImageJ.

The first number indicates which IODP sample the fossils are from, while the second indicates which hole on the physical slide they are in - some samples included more fossils than fit in a single hole, thus multiple holes were used and imaged. (See "Age-Depth Key" files)

Funding

American Philosophical Society, Award: Lewis and Clark Fund for Astrobiology 2012