Blocking temperature radiometric dating
Radiolaria have left a geological record since at least the Ordovician times, and their mineral fossil skeletons can be tracked across the K–Pg boundary.
There is no evidence of mass extinction of these organisms, and there is support for high productivity of these species in southern high latitudes as a result of cooling temperatures in the early Paleocene.
Animals in the water column are almost entirely dependent on primary production from living phytoplankton, while animals living on or in the ocean floor feed on detritus or can switch to detritus feeding.
Extinction was more severe among animals living in the water column than among animals living on or in the sea floor.
No purely herbivorous or carnivorous mammals seem to have survived.
Rather, the surviving mammals and birds fed on insects, worms, and snails, which in turn fed on dead plant and animal matter.
However, the extinction also destroyed a plethora of other terrestrial organisms, including certain mammals, pterosaurs, birds, Yet the devastation caused by the extinction also provided evolutionary opportunities.
In the wake of the extinction, many groups underwent remarkable adaptive radiations—a sudden and prolific divergence into new forms and species within the disrupted and emptied ecological niches resulting from the event.