To better understand radiolarian evolution and taxonomy, two middle Cambrian specimens recovered from Australia were studied using micro-CT. Analyses of their 3-D models revealed for the first time their skeletal architecture constructed of spicules. Insertion of an artificial sphere into their shells indicates that they may have secreted their spicules one by one during cell enlargement. The timing of skeletal genesis may be an important factor influencing the morphology of early radiolarians.

We used organic-walled microfossils to better define the Plio–Pleistocene transition (2.56 Ma) that is associated with the intensification of the Northern Hemisphere glaciation. The disappearance of species around 2.75 Ma reflects an ecological response accompanying the Greenland ice sheet growth. A strong regionalism marks the Labrador Sea and suggests cooler conditions than elsewhere in the North Atlantic, although our zone boundaries are contemporaneous with the eastern North Atlantic.