Ichthyolith (tooth and denticle) counts from DSDP 386, 596, ODP 886, 1262, IODP U1403, and Gubbio K/Pg boundary sections

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 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: While 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.